Biology GCSE

Biology GCSE glossary

1964 key terms for Biology GCSE, A to Z, each linked to the topic pages that use it.

Find a term in Biology GCSE

1964 terms found. Open a term to try a short memory check.

A

abiotic and biotic components: Chemical elements continuously cycle between living biotic communities and non-living abiotic environments such as air, water, rocks, and soil.OCR
abiotic and biotic correlations: Biotic influences such as grazing pressure or plant competition and abiotic gradients such as light intensity and soil moisture are recorded at each sampling…OCR
Abiotic component: The non-living parts of the environment, such as light intensity, temperature, moisture, soil pH and mineral content, wind and oxygen availability.AQA
Abiotic components: The non-living parts of an ecosystem, such as air, water, soil and rocks, through which materials cycle.AQA
abiotic factors: Non-living variables such as temperature, light intensity, moisture and soil pH that directly influence physiological survival and affect plant growth and…AQA, OCR
Absence of invasion and spread: The cells do not invade other parts of the body and do not travel in the blood to form tumours elsewhere.AQA
Absorption: The movement of dissolved products through the wall of the small intestine into the blood.AQA
Absorption and transport: The products of digestion are absorbed into the blood, mainly in the small intestine, and transported by the blood to cells.AQA
Absorption of soluble nutrients: Small soluble products cross the cell membrane and supply the microorganism with the soluble nutrients it needs for respiration, growth and reproduction.AQA
Accommodation: The ciliary body contains circular ciliary muscles connected to the lens by suspensory ligaments, which control lens curvature during accommodation.AQA, OCR
Accurate observation and recording: Noting the starting colour and the final colour for each test and recording what you see accurately.AQA
active site: A rigid, complementary three-dimensional shape that binds only one specific substrate to form an enzyme-substrate complex.AQA, OCR
Active site and substrate binding: The active site is a region with a shape complementary to one particular substrate, and only that substrate binds to form an enzyme–substrate complex.AQA
Active transport: Movement of sugar molecules from the gut lumen into the blood against a concentration gradient, needing energy from respiration and carrier proteins in the…AQA, OCR
active transport of minerals: Mineral ions in lower concentrations in soil than inside root cells are absorbed against their concentration gradient using carrier proteins powered by ATP.OCR
Adaptation: An inherited feature that improves an organism's chance of surviving and reproducing in its normal habitat.AQA
Adaptation and extinction: Some species cannot move or adapt quickly enough and may become extinct, reducing biodiversity.AQA
Adaptation and natural selection: Inherited features that increase survival and reproductive success, so they are subject to natural selection.AQA
Adaptation and survival: Organisms survive in extreme environments because they possess adaptations matched to those conditions, and such environments support life only where suitable…AQA
Adaptation of transport tissues: Hollow tubes reduce resistance to flow, lignin gives strength, and dead cells remove cytoplasmic obstacles.AQA
Adaptation to environmental conditions: A feature linked to its advantage in a habitat, named and then explained in how it helps the organism survive and reproduce there.AQA
Adaptations of root hair cells: A long, thin extension increases the surface area for absorption, and a large number of mitochondria supplies the energy needed for active transport.AQA
ADH: A hormone from the pituitary gland that controls how much water is reabsorbed by the kidney tubules.AQA
Adrenal glands: The glands that produce adrenaline in times of fear or stress.AQA
adrenaline: Secreted by the adrenal glands during stress or fear to trigger the fight-or-flight response, raising heart rate, dilating bronchioles, and diverting blood to…OCR
Adult body cell: A cell such as a skin cell, taken from the animal to be cloned, from which the nucleus is extracted and inserted into the enucleated egg cell.AQA
adult stem cells: Cells from mature tissues such as bone marrow that are multipotent and present fewer ethical objections and lower rejection risks if harvested from the patient.AQA, OCR
aerobic and anaerobic decomposition: Aerobic decomposition uses oxygen for efficient respiration and rapid breakdown of organic matter, releasing carbon dioxide, while anaerobic decomposition…OCR
Aerobic and anaerobic pathways: Aerobic respiration uses glucose and oxygen as reactants and releases more energy per glucose molecule, while anaerobic respiration occurs without oxygen and…AQA
Aerobic conditions: Oxygen is supplied continuously so the fungus can respire aerobically to release energy for growth and reproduction.AQA
Aerobic respiration: Respiration that takes place using oxygen, occurs mainly in mitochondria, and completely breaks down glucose to carbon dioxide and water, transferring a…AQA, OCR
Aerobic respiration and oxygen: Oxygen is needed for aerobic respiration by decomposers, so plenty of oxygen increases the rate of decay, while waterlogged or sealed conditions limit oxygen…AQA
aerobic vs anaerobic: Aerobic respiration requires oxygen whereas anaerobic respiration occurs in the absence of oxygen.OCR
Aesthetic and behavioural traits: Appearance includes traits valued for aesthetics, such as large or unusual flowers, and behavioural traits are also selected, such as a gentle nature in…AQA
Agar gel plate: A solid medium containing nutrients on which bacteria grow on the surface or within the gel, each original cell giving rise to a visible colony.AQA
agricultural biotechnology: Using gene technology in modern agriculture, which presents substantial opportunities alongside contested risks, including practical and ethical considerations.OCR
agricultural economics: Determining the point of diminishing returns where adding fertiliser yields no economic benefit, so the optimum application rate avoids financial waste.OCR
Agricultural usefulness: Usefulness includes traits improving food production, such as disease resistance in crops or higher meat or milk yield in farm animals.AQA
Agriculture: Mainly involves crop production, and plant growth hormones are used in it to control plant growth.AQA
Agriculture and medicine contexts: The two settings in which potential benefits and risks of genetic engineering should be explained, with at least one benefit and one risk for each.AQA
AIDS: The late stage of HIV infection, occurring when the body's immune system becomes so badly damaged it can no longer deal with other infections or cancers.AQA, OCR
Air pollution: Pollution that can occur in air, from smoke and acidic gases.AQA
airborne droplets: Water droplets from coughing or sneezing that carry pathogens through the air, spreading diseases such as influenza and measles.OCR
Airborne spread: Pathogens carried in droplets or aerosols breathed out by an infected host, as with influenza.AQA
Algae: Producers that include microscopic phytoplankton in water as well as larger seaweeds, so level 1 is not restricted to land plants.AQA
allele diversity: High genetic diversity ensures that if an environmental disturbance occurs, some individuals will possess alleles conferring survival advantages.OCR
allele frequency: A measure that increases over time as surviving individuals pass their advantageous alleles to their offspring.OCR
Allele frequency change: The frequency of favourable alleles in the population increases across generations.AQA
Allele frequency in populations: The frequency of the beneficial allele increases in the population over generations.AQA
Allele notation: Genetic diagrams use a capital letter for the dominant allele and the same letter in lower case for the recessive allele.AQA
allele segregation: Alleles separate into gametes, so offspring inherit one allele from each parent.OCR
Alleles: Each gene may have different forms, and these different versions of the same gene give rise to variations in a characteristic.AQA
Alleles and genetic variation: The two members of a pair carry the same genes in the same order, though they may carry different versions called alleles, which is why characteristics can…AQA
allicin: An antibacterial chemical produced by garlic as a chemical defence.OCR
Alveoli: Tiny air sacs where gas exchange occurs, each surrounded by a dense capillary network.AQA
Amino acid interactions: Folding involves interactions between amino acids, such as hydrogen bonds and disulfide bridges.AQA
Amino acid sequence: The precise sequence in which amino acids are joined together, determined by the sequence of bases on the template, so the protein can fold into a functional…AQA, OCR
amino acids as monomers: Individual subunits that link to synthesize protein polymers.OCR
Ammonia: The nitrogen-containing product formed when the amino group is converted during deamination.AQA
Amylase: Produced in the salivary glands and the pancreas, it acts on starch, breaking it down to sugars such as maltose.AQA
Anabolic and catabolic reactions: Anabolic reactions build new molecules, such as amino acids joining to form proteins, while catabolic reactions break molecules down, such as glucose being…AQA
Anaerobic decay: When microorganisms break down biological material without oxygen, the process is called anaerobic decay, which produces methane gas.AQA
Anaerobic respiration: Respiration that takes place without oxygen, occurs in the cytoplasm, and partially breaks down glucose, transferring less energy per glucose molecule because…AQA, OCR
Anaerobic respiration and lactic acid production: Muscle cells may respire anaerobically when oxygen supply cannot keep pace with demand, producing lactic acid which accumulates and contributes to fatigue.AQA
Analysis and interpretation of data: Comparing zones and deciding which substance is most effective, using comparative language such as larger zone, more effective.AQA
Angioplasty: A procedure in which a balloon catheter is guided to the narrowed section and the balloon is inflated to push the atheroma aside.AQA
Animal welfare: A concern that these methods may raise, since restricted movement may cause distress.AQA
anomalous data: Obvious anomalous readings should be excluded before calculating the mean reaction time.OCR
antagonistic hormones: Two hormones where insulin lowers blood glucose while glucagon raises it, so each reverses the change that triggered the other.AQA, OCR
Antibacterial chemicals: Substances that inhibit or kill bacteria, lowering the chance of infection entering damaged tissue.AQA
Antibiotic clear zones: When comparing clear areas around colonies, calculate each area separately and compare the values to judge which microorganism is more affected by an…AQA
Antibiotic resistance: Evolves when random mutations produce resistant bacteria, and the antibiotic selects these by killing susceptible ones, so the proportion of resistant…AQA, OCR
antibiotic resistance markers: Genes on the plasmid used to select successfully transformed bacteria, as only bacteria carrying the recombinant vector survive on antibiotic-treated agar.OCR
Antibiotics: Treatments that kill bacteria or inhibit their growth, and so can treat bacterial infections but are ineffective against viruses.AQA
Antibiotics and painkillers: Antibiotics kill bacteria or stop their growth, while painkillers relieve symptoms but do not kill pathogens.AQA
Antibiotics and treatment: Antibiotics such as penicillin can kill the pathogen, and penicillin was originally an effective and easily used treatment for gonorrhoea.AQA
antibiotics versus antivirals: Antibiotics specifically kill bacteria or inhibit their growth without harming human cells but are ineffective against viruses, whereas antivirals inhibit…AQA, OCR
antibodies: Proteins secreted by plasma cells that bind specifically to antigens, causing agglutination or tagging pathogens for phagocytosis.OCR
Antibody production: Lymphocytes produce antibodies that bind to antigens on a specific pathogen, which can clump pathogens together, neutralise them or help other white blood…AQA
Anticoagulant medicine: Medicine that patients with mechanical valves usually need for life because the valves increase the risk of blood clots.AQA
antidiuretic hormone: Synthesised by the hypothalamus and secreted by the posterior pituitary gland, it regulates the water permeability of the kidney collecting ducts.OCR
antigen detection: Detection of pathogen-specific antigens using monoclonal antibody test kits, such as rapid flow tests.OCR
antigen detection with antibodies: Laboratory detection of the antigen from the disease causing organism, using monoclonal antibody test kits that bind pathogen-specific antigens.OCR
Antigen specificity: Monoclonal antibodies bind to one specific antigen because their binding sites are complementary to it.AQA
Antigen stimulation: An antigen triggers the lymphocyte to produce its specific antibody, which does not necessarily cause disease.AQA
Antigen-antibody specificity: An antibody is specific to one binding site on one protein antigen, so it binds only where the complementary antigen is present.AQA
Antigen–antibody binding: White blood cells secrete specific antibodies that bind to antigens on the pathogen, leading to its destruction.AQA
antigens: Unique molecular markers on the surface of pathogens that lymphocytes recognise as non-self.OCR
Antigens and antibodies: Antigens from the pathogen are recognised as foreign, and white blood cells called lymphocytes produce antibodies that are specific to those antigens.AQA
antimicrobial compounds: Chemicals synthesised by plants that destroy or inhibit bacterial and fungal pathogens.OCR
Antiretroviral drugs: Treatment that can control HIV by suppressing viral replication rather than curing the infection, so it must be continued.AQA
Antiretroviral treatment: Effective treatment that can prevent HIV from progressing to AIDS, so late stage HIV is not inevitable.AQA
antiseptic chemicals: Non-specific chemical antimicrobials applied externally to living skin to destroy pathogens and prevent wound infection.OCR
Antitoxin production: White blood cells produce antitoxins that neutralise toxins released by pathogens.AQA
Antitoxins: Substances that neutralise toxins produced by bacteria, not the pathogens themselves.AQA
Apex predator: A carnivore at the top of a food chain or web with no predators of its own in that ecosystem.AQA
apex predators: Tertiary consumers at the top of the food chain that have no natural predators.OCR
Aphids: Insects that feed on plant sap and can weaken plants, and also act as vectors, transmitting viruses between plants.AQA
Apparatus and measurement skills: Selecting and using apparatus such as measuring cylinders or syringes to measure volumes of starch, amylase and buffer solutions.AQA
Apparatus and techniques: Specific equipment and methods used when investigating photosynthesis, identified by AT codes.AQA
Application of knowledge: Using knowledge of mitosis in unfamiliar contexts by looking for clues such as growth, repair or asexual reproduction and linking the situation to mitosis.AQA
Application of knowledge to unfamiliar contexts: Using the principle of specific binding with information supplied in a question rather than recalling a memorised example.AQA
Application to unfamiliar organisms: You should be able to apply your understanding of asexual and sexual reproduction to explain advantages and disadvantages for an unfamiliar organism when a…AQA
Applications in animals, plants and microorganisms: Genes are transferred to the cells of animals, plants or microorganisms so that they develop with desired characteristics.AQA
Applications of genomics in medicine: Medical uses include predicting risk of conditions, choosing treatments that suit a person's genetic make-up, designing new medicines, and understanding…AQA
Appropriate prescribing: Doctors should prescribe antibiotics only for serious bacterial infections where they are likely to be effective, and only when there is a clear bacterial…AQA
Appropriate scales: A scale that uses most of the available axis and gives evenly spaced major intervals, with each axis labelled with quantity and unit.AQA
Appropriate use of antibiotics: Antibiotics are the medicines that kill bacteria, so they are used only for bacterial infections.AQA
approximation: A sensible value produced by estimation, rounded to one or two significant figures rather than excessive decimal places.OCR
Areas of decay: Regions of soft, broken-down plant tissue, often on fruit, roots or stems.AQA
arteries: Blood vessels that carry blood away from the heart and have thick, muscular and elastic walls to withstand and maintain high blood pressure.AQA, OCR
Artificial pacemaker: An electrical device used to correct irregularities in the heart rate.AQA
artificial selection: Another name for selective breeding, in which humans deliberately choose individuals with desirable traits to breed together.AQA, OCR
Aseptic technique: The method of preparing an uncontaminated culture by sterilising equipment and media, cleaning work surfaces, washing hands and keeping the lid closed or only…AQA
Aseptic technique and risk management: Using aseptic technique, keeping lids on and following safe disposal to make informed judgements about risks such as contamination or growth of pathogens.AQA
Aseptic technique and safe culturing: Culturing bacteria requires aseptic technique, sterilised equipment and incubation at a safe school temperature, no higher than 25 °C.AQA
aseptic techniques: Measures that prevent contamination of pure microbial cultures and protect the investigator.OCR
Asexual reproduction: Produces genetically identical offspring by mitosis, so it is rapid, requires only one parent and is efficient when conditions are stable, but gives no…AQA, OCR
Asexual reproduction and cloning: Reproduction producing genetically identical offspring from one parent, without gametes or fertilisation, which is why it is described as cloning.AQA
Asexual versus sexual reproduction: Many fungi reproduce asexually by spores but also reproduce sexually to give variation.AQA
aspirin: An analgesic medicine extracted from salicin in willow bark, developed from plant defence chemicals.OCR
Atheroma: Fatty material that builds up in the artery wall and narrows the lumen.AQA
atmospheric gases and water availability: Conditions whose changes affect organisms, with sulfur dioxide affecting lichen distribution and drought or altered rainfall forcing migration and geographic…OCR
ATP: The substance to which the energy released is transferred, which powers cell activities.AQA
ATP (Adenosine Triphosphate): The molecule that stores and transfers energy in cells, often called the 'universal energy currency'.OCR
ATP supply: The continuous provision of ATP in all living cells by cellular respiration, which never ceases.OCR
ATP yield: Aerobic respiration produces a high yield of ATP while anaerobic respiration produces a low yield of ATP per glucose.OCR
autoclaving: Sterilises glassware and nutrient agar growth media using steam under pressure at 121 °C.OCR
Autosomes and sex chromosomes: The first 22 pairs of chromosomes are autosomes and carry genes that control general characteristics, while the 23rd pair are the sex chromosomes and carry…AQA
autotrophs: Organisms that synthesize organic compounds from inorganic precursors and function as producers.OCR
Auxin and cell elongation: Auxin is a plant hormone made in the shoot and root tips that causes cells to elongate, so a higher auxin concentration leads to more growth on that side.AQA
Auxin mechanisms: Unequal distribution of auxin causes unequal growth rates, stimulating cell elongation in shoots but inhibiting it in roots.AQA
Auxin uses: These depend on auxin promoting or disrupting normal growth and development, as a weed killer, as a rooting powder and in tissue culture.AQA
auxins: Plant hormones synthesised in actively growing shoot tips and root tips and transported to zones of elongation.OCR
axis labels and units: Axes labelled fully with the correct variable names and SI units, such as Time in days or Biomass in g/m².OCR
axis scaling: Linear, regular scales chosen so that plotted points occupy at least half the available grid space in both dimensions.OCR

B

Bacteria: Single-celled organisms that can divide rapidly and may release toxins.AQA
Bacterial chromosome: The main circular DNA molecule that sits free in the cytoplasm, usually as a single loop.AQA
Bacterial disease: A disease caused by a bacterium, such as gonorrhoea, which can be treated with antibiotics such as penicillin.AQA
Bacterial hosts and plasmids: Bacteria are useful hosts because they reproduce rapidly and can be grown on a large scale, and a plasmid is a small circular DNA molecule used as a vector.AQA
Bacterial mutation: Random mutations can arise in bacterial populations and some reduce the effect of an antibiotic.AQA
Bacterial reproduction: Surviving resistant bacteria reproduce, often rapidly by binary fission, passing the resistance allele to their offspring.AQA
bacterial selection: Non-resistant bacteria are killed by antibiotics while resistant bacteria survive, reproduce, and pass on resistance alleles.OCR
Balanced argument and judgement: Presenting more than one side of the importance of understanding the human genome and reaching a judgement, weighing benefits against concerns.AQA
bar charts: Display categorical, discontinuous health data with distinct gaps between bars, for example rates of bacterial versus viral infections or blood groups.OCR
bark: Layers of dead cells on tree trunks that shed regularly, carrying pathogens away.OCR
Bark and dead cell layers: Layers of dead cells around stems that protect deeper living tissues and eventually fall off, carrying pathogens away.AQA
Barrier and physical methods of contraception: Non-hormonal methods act physically or chemically: condoms block sperm and also reduce infection risk, and diaphragms need correct fitting.AQA
Barrier contraception: A method such as a condom that physically prevents the exchange of body fluids during sexual contact, so the bacterium cannot move from an infected person to…AQA
barrier methods: Non-hormonal physical barriers such as condoms, which have lower theoretical effectiveness due to user error but provide protection against sexually…AQA, OCR
Barriers against microorganism invasion: The named physical defences of plants, each linked to how it prevents microorganisms entering or spreading.AQA
Barriers to treatment: Difficulties including the blood-brain barrier limiting which drugs reach the brain and surgery risking damage to healthy tissue.AQA
Basal metabolic rate: The rate at which the body uses oxygen and energy while at rest, which thyroxine stimulates.AQA
Base of the food chain: The position occupied by producers, which do not eat other organisms and are always numbered 1.AQA
Base sequence: The order of bases within a gene, read in triplets, which fixes the order of amino acids.AQA
Behavioural adaptations: Actions or patterns of behaviour carried out by the organism, such as migrating, hibernating, basking in the sun or hunting at night.AQA
Benedict's solution: Added to the sample and heated in a water bath, a colour change towards brick-red indicates a reducing sugar.AQA
Benedict’s test for reducing sugars: Benedict’s solution is blue and, when heated with a reducing sugar such as glucose, changes through green and yellow to brick-red, reflecting how much…AQA
Benefits and risks: The potential advantages and possible negative outcomes of genetic engineering, which students should explain for agriculture and medicine.AQA
Benefits and risks of major surgery: Transplantation can improve survival and quality of life, but there are risks such as infection and rejection.AQA
Benign tumour: A growth of abnormal cells which is contained in one area, usually within a membrane.AQA
benign tumours: Abnormal cell masses contained within a membrane that do not invade surrounding tissues or spread.OCR
Beta-carotene: A substance made by golden rice grains that the human body converts into vitamin A.AQA
Bias and random selection: A sample must be selected without bias, for example by random selection, so that the sample represents the population.AQA
biconcave disc: A shape that provides a high surface area to volume ratio, maximizing oxygen diffusion rates.OCR
Bile: A digestive fluid made in the liver and stored in the gall bladder before release.AQA
Bile ducts: Tubes along which bile travels from the liver to the gall bladder.AQA
Binary fission: Asexual reproduction in which one bacterial cell divides into two genetically identical daughter cells, with the circular DNA replicated and the cell dividing.AQA
Binomial naming: The scientific name of an organism is formed from its genus and species, for example Homo sapiens, and is written in a standard way.AQA
Binomial system: A system in which organisms are named by genus and species, with the name always written as genus followed by species, never reversed.AQA
Biochemical evidence and DNA sequencing: Comparing DNA base sequences, amino acid sequences in proteins and metabolic pathways provides measurable data about relatedness between organisms.AQA
Biodiversity: The variety of living things, which can be reduced when fewer insects survive because wild flowers have declined.AQA
biodiversity conservation: Modern conservation guided by evolutionary principles, using seedbanks to store plant seeds and preserve genetic diversity.OCR
Biodiversity loss: Biodiversity can fall if species cannot adapt or relocate quickly enough, and some may become extinct.AQA
biodiversity preservation: Conservation initiatives such as nature reserves, captive breeding for reintroduction, wetland restoration and legal hunting prohibitions preserve biodiversity.OCR
bioethics and germline editing: Ethical dilemmas include astronomical treatment costs creating unequal access and moral controversies surrounding germline editing that permanently alters…OCR
biofortification and ethics: Nutritional enrichment such as Golden Rice biofortified with beta-carotene, alongside ethical and socioeconomic concerns about farmers becoming dependent on…OCR
Biogas generators: These are airtight vessels designed to carry out anaerobic decay on a large scale, in which waste biological material is placed so that oxygen is excluded.AQA
bioindicator species: Organisms that provide biological evidence, such as lichens revealing atmospheric sulfur dioxide levels or freshwater invertebrates indicating aquatic organic…OCR
Biological catalysts: Proteins that act as biological catalysts in living organisms, lowering the activation energy needed for a reaction so it happens faster at body temperature.AQA
biological control: Using natural predators or parasites to control pest numbers without chemical residues.OCR
Biological drawing skills: Making a drawing with a sharp pencil using clear, continuous, unshaded lines, large enough to show detail, with labels, a title and, where relevant, a scale…AQA
Biological polymers: Large molecules built from many repeating smaller units, such as DNA, which is built from repeating nucleotide units.AQA
Biological valves: Valves taken from an animal such as a pig or cow, or from a human donor, which tend to work well without long-term anticoagulant medicine but may wear out…AQA
Biomass: The mass of biological material synthesized by organisms, formed as glucose is converted into biological macromolecules.AQA, OCR, Pearson Edexcel
Biomass as living material: The mass of living material, often measured as dry mass per unit area, for example in grams per square metre (g/m²).AQA
Biomass harvesting and purification: The dense biomass is harvested from the fermenter and purified so that it is safe and suitable to use as food.AQA
Biomass transfer between trophic levels: Only a fraction of the glucose taken in becomes new biomass available to the next trophic level, because most of it is respired to power the organism's life…AQA
Biotechnology applications: Useful uses of extremophile enzymes, such as heat-stable DNA polymerase used in the polymerase chain reaction.AQA
Biotic component: The community of living organisms, including their relationships such as feeding, pollination and decomposition.AQA
Biotic components: The living parts of an ecosystem, such as plants, animals and decomposers, through which materials cycle.AQA
biotic factors: Living influences on a community, such as the availability of food, new predators arriving, new pathogens, or one species outcompeting another.AQA, OCR
Biuret reagent: Added to the sample, a colour change from blue to purple indicates protein.AQA
Biuret test for protein: Biuret reagent is blue and turns purple when protein is present.AQA
Black spot: A fungal disease, common on roses, that produces dark spots on leaves and can cause leaf loss.AQA
Blood glucose homeostasis: When blood glucose falls too low, glucagon causes glycogen to be converted into glucose and released into the blood.AQA
blood glucose regulation: The process in which insulin increases glucose uptake from blood plasma and its conversion to glycogen, reducing circulating concentration back towards the…AQA, OCR
blood plasma: A pale straw-coloured aqueous solvent that transports dissolved nutrients, waste products, hormones, antibodies and thermal energy.OCR
Blood transport of hormones: The blood carries the hormone from the secreting gland to a target organ where it produces an effect.AQA
blood-brain barrier: A selective barrier that severely restricts the diffusion of many therapeutic pharmaceutical drugs into cerebral tissues.OCR
blotting: Cylinders are rolled gently on a paper towel to remove surface water without squeezing tissue, before being reweighed.OCR
Blurred vision: What occurs in both defects because the rays of light do not focus on the retina.AQA
boundary layer: The layer at the leaf surface from which increased air movement sweeps away accumulating water vapour, maintaining a steep concentration gradient.OCR
Bowman's capsule and ultrafiltration: A cup-shaped structure surrounding the glomerulus, where high hydrostatic pressure drives ultrafiltration of small molecules into the tubule.OCR
Brain: A processing centre that receives information from receptors, integrates it and issues instructions.AQA
Brain imaging techniques: Indirect methods such as MRI or EEG scans that show activity patterns rather than giving definitive explanations of living brain function.AQA
Branching diagrams as models: These show proposed relationships between organisms and may be revised when new data become available.AQA
Breakdown reactions: Reactions that split larger molecules into smaller ones.AQA
Breath volume: The volume of air moved per breath, which increases during exercise to take in more oxygen and remove more carbon dioxide.AQA
Breathing rate: How often breaths are taken, which increases during exercise to take in more oxygen and remove more carbon dioxide.AQA
Breathlessness and tiredness: Symptoms that both faults may cause, along with reduced efficiency of the heart.AQA
Breeding population: The part of a stock that reproduces; as it shrinks, fewer young fish are produced, so the stock falls further.AQA
Breeding programmes: These keep endangered species alive and produce offspring for release into suitable wild habitats.AQA
Breeding true for a characteristic: The endpoint is a population in which essentially all offspring show the desired characteristic.AQA
Bronchi: The two tubes that branch from the trachea and enter the lungs, then branch into smaller airways that end at alveoli.AQA
bubble counting: Counting bubbles released per minute from pondweed as a direct, simple measure of photosynthetic rate, though bubble volume varies and rapid bubbling is hard…OCR
Building blocks for life: Recycled materials provide the building blocks, such as carbohydrates, proteins and nucleic acids, for future organisms.AQA
Building blocks of carbohydrates, proteins and lipids: Sugars, amino acids, fatty acids and glycerol are the small molecules used to synthesise larger storage and structural molecules.AQA
Bulb division: Asexual reproduction in daffodils where the parent bulb forms smaller daughter bulbs that grow into new plants.AQA
Bunsen burner: A heating device used with a beaker of water supported on a tripod and wire gauze, set to a blue heating flame rather than direct flame heating.OCR

C

cancer: A condition resulting from changes in cells that lead to uncontrolled growth and division, forming a tumour.AQA, OCR
Capillaries: Microscopic vessels with walls one cell thick that link arteries and veins, allowing exchange of substances with tissues.AQA
Capillary network: The blood supply surrounding the alveoli that receives oxygen and releases carbon dioxide, bringing blood close to the alveolar surface.AQA
capture-mark-recapture: Estimates mobile animals using the Lincoln index, ensuring marking does not harm or increase predation risk.OCR
Carbohydrases: Enzymes that catalyse the breakdown of carbohydrates into simple sugars.AQA
Carbohydrate controlled diet: Limits the amount of carbohydrate eaten, reducing glucose absorbed into the blood so fewer and smaller rises in blood glucose occur after meals.AQA
Carbohydrate storage: Excess glucose is converted to glycogen in liver and muscle cells, acting as a reserve of glucose.AQA
Carbon and mineral ion cycling: The return of carbon and mineral ions to the environment by decomposition, keeping matter available to producers.AQA
carbon cycle: Balances atmospheric carbon dioxide through photosynthesis, cellular respiration, decomposition and combustion, ensuring a continuous flow of carbon for…AQA, OCR
Carbon cycle processes: Carbon enters plants as carbon dioxide during photosynthesis and returns to the air when organisms respire, when decomposers break down dead matter, and when…AQA
Carbon dioxide: A greenhouse gas released into the atmosphere by burning fossil fuels.AQA
carbon dioxide concentration: Increasing this provides more carbon substrate for fixation into glucose, linearly accelerating the rate until saturation.OCR
Carbon emissions: Transport consumes fuel and releases carbon dioxide, adding environmental cost.AQA
carcinogens: Agents such as UV radiation, ionising radiation, and chemicals in tobacco smoke that cause cancer mutations.OCR
cardiac muscle: Myogenic muscle that the mammalian heart consists of, partitioned into four chambers.OCR
cardiac output: Calculated by multiplying heart rate in beats min⁻¹ by stroke volume in cm³ per beat.OCR
cardiovascular disease: A disease whose risk is linked to smoking, high blood pressure, inactivity and family history.OCR
Cardiovascular health: A diet high in saturated fat raises blood cholesterol, leading to fatty deposits in arteries and cardiovascular disease, while smoking damages blood vessels…AQA
carnivore: An organism whose diet consists of other animals, such as the secondary consumer that eats herbivores.AQA
Carrier: A person with one recessive allele who does not show the disorder but can pass the allele on to their children.AQA
carrier identification: Identifying two unaffected parents who produce an affected child, proving both are heterozygous carriers of a recessive allele.OCR
Carrier molecules: Molecules that bring specific amino acids to add to the growing protein chain in the correct order, each being specific to one type of amino acid.AQA
Carrier proteins: Proteins in the membrane that are used, with energy from respiration, to move substances from a lower concentration to a higher concentration in active…AQA
Carrier proteins and membrane transport: Proteins in the cell membrane that use energy to change shape and transport specific substances across the membrane.AQA
Carrier proteins and selectivity: Carrier proteins in the membrane are specific, so active transport allows selective uptake of particular substances.AQA
Carriers: Heterozygous organisms who do not show the recessive characteristic but can pass on the recessive allele.AQA
carrying capacity: The level determined by food availability, which acts as a biotic factor controlling population size within a community.OCR
Causal mechanism: An explanation of how a risk factor produces a disease, describing the biological process rather than just the association.AQA
Causal mechanisms in disease: A causal chain links the first disease to the second, such as a weakened immune system allowing a secondary infection.AQA
Causation of disease: The microorganism itself, not a toxin in food or a genetic fault, triggers the illness.AQA
Cause and effect: Linking each hormone to the next, such as FSH causing oestrogen secretion, rather than describing the hormones as acting independently.AQA
Cause and effect in disease: A defect means defences work less effectively, so pathogens are not destroyed efficiently, multiply and cause infectious disease more often and often more…AQA
Causes of ill health: Diseases, both communicable and non-communicable, are major causes of ill health.AQA
Cell: The basic building blocks of all living organisms, and the smallest unit that can carry out all the processes we associate with life.AQA
Cell culture: Growing cells in the laboratory, where cloning produces many genetically identical stem cells by mitosis.AQA
cell cycle: A series of stages in which a cell grows, copies its genetic material and divides to form two genetically identical cells.AQA, OCR
Cell cycle completion: The cytoplasm and cell membranes divide to form two identical cells, after the nucleus has divided.AQA
Cell cycle stages: The three broad stages are growth and DNA replication, mitosis, and cytokinesis, and their order and purpose must be known.AQA
Cell damage and symptoms: The host cell is often damaged or destroyed when the new viruses burst out, and this cell damage produces the symptoms of the viral disease.AQA
Cell differentiation: The process by which a cell becomes specialised for a particular function by switching on specific genes and producing particular proteins.AQA, OCR
cell dimensions: A typical eukaryotic animal cell measures approximately 10 to 30 µm across, a plant cell 10 to 100 µm, and a bacterium 1 to 5 µm.OCR
Cell division and cloning: Hybridoma cells are cloned to produce many identical cells, all manufacturing the same monoclonal antibody.AQA
Cell division and mitosis: In mature animals, most growth is complete, so division by mitosis is not used for general growth as it is in young organisms.AQA
cell elongation: The process stimulated by higher auxin concentration on the shaded side, causing the shoot to curve towards the light source.OCR
Cell fusion and hybridomas: A specific lymphocyte and a tumour cell are fused together to produce a single hybridoma cell.AQA
Cell growth: The increase in size and mass of a cell before it divides, building up its cytoplasm and sub-cellular structures.AQA
Cell membrane: The partially permeable barrier that controls what enters and leaves the cell.AQA
Cell membrane function: Every cell is surrounded by a cell membrane that controls what enters and leaves.AQA
cell membranes: Consist of a lipid bilayer embedded with receptor molecules, providing a selectively permeable barrier controlling solute exchange.OCR
Cell nucleus transfer: The nucleus is removed from an egg cell, and a nucleus from one of the patient's body cells is inserted into the empty egg cell.AQA
Cell respiration: A chemical process in cells in which sugar is broken down to release energy.AQA
Cell sap: A solution of sugars, salts and other solutes that fills the permanent vacuole.AQA
Cell specialisation: When cells become specialised so that different jobs are shared between different cell types, which is important in multicellular organisms.AQA
Cell specialisation and mitochondria: Cells that carry out a lot of active transport have many mitochondria to release energy by aerobic respiration.AQA
Cell structure: The visible structures labelled in observed cells, such as the nucleus, cytoplasm, cell membrane, cell wall and vacuole.AQA
Cell wall: A structure outside the cell membrane of plant and algal cells, made of cellulose, which strengthens the cell.AQA
Cells to tissues: Specialised cells group together to form tissues, which build organs and organ systems.AQA
Cells, tissues and whole organisms: The three main biological systems used in preclinical testing: cultured cells, isolated tissues and live animals.AQA
cellular magnification: Total magnification is the eyepiece magnification multiplied by the objective magnification, for example 10 x 40 = 400x.OCR
Cellular respiration: A continuous process occurring in every living cell that transfers energy from chemical stores in glucose to power vital cellular activities.AQA, OCR
Cellular respiration and metabolism: Respiration transfers energy from glucose, and this energy is used by the organism for the enzyme-controlled processes of metabolism.AQA
Cellulose: A carbohydrate polymer of glucose units that forms strong fibres resisting stretching, and is the material of the cell wall.AQA
cellulose cell wall: A tough mechanical barrier composed of cellulose microfibrils around individual plant cells, stopping bacterial and fungal hyphae from invading the cytoplasm.OCR
Cellulose cell walls: Strong and rigid structures surrounding each cell that resist penetration by fungal hyphae and bacteria.AQA
Central nervous system: The body's main processing centre, consisting of two linked organs: the brain and the spinal cord.AQA
cerebellum: Located at the back of the brain, it coordinates voluntary muscular movement, motor skills, posture, and balance.AQA, OCR
Cerebral cortex: The large folded outer layer of the brain, responsible for consciousness, intelligence, memory and language.AQA
cerebrum: The large, highly folded outer hemispheres responsible for conscious thought, voluntary motor commands, intelligence, memory, emotion, and language.OCR
Change from wild ancestors to domesticated varieties: Domestication produced populations that differ from their wild ancestors.AQA
Change in populations over generations: The proportion of individuals with the useful characteristic increases over generations.AQA
Change over geological time: A fossil closely resembling a modern species indicates that the organism has changed little over time, while a fossil very different from any living species…AQA
Changing classification: Classification systems change as biological knowledge grows, and new evidence can move organisms into different groups or create new groups.AQA
Changing diets: In developed countries, people eat more varied diets and demand foods that cannot be grown locally all year.AQA
Chemical defences: Substances produced by a plant that reduce harm from herbivores or pathogens.AQA
Chemical digestion: Efficient chemical digestion in the duodenum needs alkaline conditions as a necessary preparation, not a digestive action by bile itself.AQA
Chemical responses: Hormones are carried in the blood plasma, and this is slower but longer-lasting, suiting sustained regulation.AQA
Chemical synthesis in industry: Most new drugs are synthesised by chemists in the pharmaceutical industry, often modifying the original molecule.AQA
Chemosynthesis in the absence of light: Light does not penetrate to these vents, so the bacteria may obtain energy by chemosynthesis rather than photosynthesis.AQA
chlorophyll: The light-trapping green pigment contained in chloroplasts, which absorbs light energy.AQA, OCR
chloroplasts: Sub-cellular organelles containing the light-trapping green pigment chlorophyll, within which photosynthesis takes place.AQA, OCR
Chlorosis: Pale or yellow leaves caused by too little chlorophyll, so less light is absorbed and less glucose is made, which also limits growth.AQA
choice chamber behavioral testing: Investigating taxis responses to light or humidity in invertebrates, transferred gently and kept with adequate moisture and ventilation rather than left for…OCR
Cholesterol: A fatty substance carried in the blood, where a high level is linked to the build-up of fatty material in artery walls.AQA
Chromosome: One enormously long DNA molecule that can hold hundreds or even thousands of genes arranged along its length.AQA
Chromosome copies: Each chromosome consists of two identical copies, often called sister chromatids, held together until mitosis separates them.AQA
Chromosome number in humans: In humans this means 46 chromosomes arranged as 23 pairs.AQA
Chromosome separation: The process in which the chromosome copies line up at the centre of the cell and are pulled apart by spindle fibres.AQA
chromosome theory: The discovery of chromosome behaviour during meiosis provided the physical evidence validating Mendel laws.OCR
chromosomes: Structures in which the DNA is contained, found in the nucleus of eukaryotic cells.AQA, OCR
Chromosomes and genes: In the early 20th century chromosomes and Mendel's 'units' behaved in similar ways, leading to the idea that the 'units', now called genes, were located on…AQA
Chromosomes and inheritance: Human body cells contain 46 chromosomes arranged as 23 pairs, with one chromosome of each pair inherited from each parent.AQA
Ciliary muscles: These contract when focusing on a near object, and their contraction reduces tension in the suspensory ligaments.AQA
Circular area calculation: A colony or a clear area around a colony is roughly circular, so its cross-sectional area is calculated using the formula for the area of a circle, A = πr².AQA
circulatory transport: Hormones are transported throughout the body within blood plasma.OCR
Classification: Sorting living things into groups based on shared features, traditionally depending on their structure and characteristics.AQA
Classification of adaptations: Grouping adaptations by the main process involved, naming the adaptation, placing it in the correct category and explaining how it helps the organism survive…AQA
classification systems: Systems that group organisms, having transitioned from artificial systems based on observable morphological traits to natural phylogenetic systems reflecting…OCR
clinical human trials: Commence on humans if cleared, with Phase 1 administering very low doses to healthy volunteers to check safety and side effects.OCR
clinical risk factors: Underlying non-communicable disease risk factors identified by translating physiological measurements into quantitative risk categorisations.OCR
Clinical trials: Testing proceeds in phases: healthy volunteers check safety and side effects, patients test effectiveness and optimum dose, and large-scale trials compare the…AQA
clone: The offspring that results when the embryo develops, being genetically identical to the adult body-cell donor.AQA
Clones: Offspring that are genetically identical to the parent because all their cells arise by mitosis from the parent tissue.AQA
Cloning: Produces genetically identical offspring from a single parent cell or organism, so the offspring have the same genes as the parent.AQA
Closed system: A continuous network of tubes in which the three vessel types form a circuit: heart, arteries, capillaries, veins and back to the heart.AQA
coding DNA: DNA in which a variant can change the amino acid sequence and therefore alter the activity of the protein produced.AQA
codon: A complementary mRNA sequence transcribed from a DNA template triplet, read in order by the ribosome to assemble the protein.AQA
Codons: Groups of three mRNA bases read by the ribosome, each specifying one amino acid.AQA
Coefficient: The value A in standard form, which must be at least 1 and less than 10, and is adjusted with the index if needed.AQA
Cohesion and tension: Evaporation from leaves creates tension that pulls the water column up the stem, depending on the continuous, reinforced plumbing that xylem provides.AQA
Collaboration and priority in science: Alfred Russel Wallace independently reached similar conclusions, prompting Darwin to publish.AQA
collateral damage: Attempting surgical excision of tumours or repair of severed pathways risks causing irreversible damage to adjacent healthy neural tracts.OCR
collecting duct permeability: Increased when antidiuretic hormone binds to receptors on the collecting duct walls, causing aquaporin channels to insert into cell membranes.OCR
Collection of eggs: Mature eggs are collected from the mother's ovaries before they are naturally released, increasing the chances of successful fertilisation in the laboratory.AQA
Colony: A visible cluster of genetically identical cells descended from one parent cell, so colonies can be counted to estimate numbers of viable bacteria.AQA
Colony growth: The cross-sectional area of a colony is calculated using A = πr², with the radius found by halving the measured diameter.AQA
colorimetric and indicator endpoints: Timing a colour change until an end point, such as iodine no longer turning blue-black as amylase digests starch, or milk clearing with trypsin, where rate…OCR
colour blindness: An inherited condition caused by faulty or absent cone pigments in the retina.OCR
Combined causation: Many characteristics result from a combination of genes and the environment, where genes set a potential range and the environment influences where an…AQA
Combining multiple evidence sources: Using both current classification data and fossil data, which gives a more complete picture of evolutionary relationships than either source alone.AQA
Combustion and energy transfer: Burning peat as a fuel is combustion, which also releases carbon dioxide.AQA
Combustion of fossil fuels: Burning fossil fuels, which releases carbon dioxide as an additional human source rather than a return from living organisms.AQA
commercial applications: Commercial growers use this knowledge in glasshouses, providing artificial light, heating and CO₂ to maximise the rate of photosynthesis and increase crop…OCR
commercial horticulture: One of the areas where synthetic and natural plant hormones are widely exploited to manipulate crop development.OCR
Common ancestry: This evidence supports the idea that life has evolved and that species are related through common ancestors.AQA
Common ancestry and relatedness: Species sharing a more recent common ancestor are more closely related than species whose lineages split earlier.AQA
Common sugar and phosphate: The sugar and phosphate are common to all nucleotides, so the four nucleotides differ only in which base is attached.AQA
Communicable and non-communicable disease interaction: A communicable disease can weaken the body so a non-communicable disease develops, or a non-communicable disease can make a communicable infection more likely…AQA
Communicable and non-communicable diseases: A communicable disease may weaken the body, making a non-communicable disease more likely or more severe.AQA
Communicable diseases: Diseases caused by pathogens such as bacteria, viruses, fungi and protists, and can be transmitted from person to person or from other organisms.AQA, OCR
Community: The populations of different species living together in a habitat.AQA
community distribution: How species are spread within an ecological community, governed by dynamic interactions with abiotic and biotic factors.OCR
Community health: Combining methods such as draining water, nets and repellents reduces malaria transmission in a community more effectively than one method alone.AQA
companion cells: Cells with abundant mitochondria that actively load sucrose into sieve tubes.OCR
Comparative analysis: Comparing data for different groups, for example smokers and non-smokers, using values from the graph or table and comparative vocabulary such as higher,…AQA
Comparing fossil and living structures: Fossils show the structure of past organisms, and comparing these structures with those of living organisms reveals similarities and differences.AQA
Comparison: Comparing two organisms and identifying the rank at which they diverge.AQA
competition: Organisms competing for limited resources: plants for light, space, water, and minerals; animals for food, territory, and mates.AQA, OCR
Competition for limited resources: Competition occurs when resources are limited, with plants competing for light, space, water and mineral ions and animals for food, mates and territory.AQA
Complementary base pairing: The bases pair in a specific way: A always pairs with T, and C always pairs with G, holding the two strands of the double helix together.AQA, OCR
Complementary shapes and molecular recognition: The antibody's binding site has a shape complementary to the antigen, like a lock and key, so only one antigen fits.AQA
Completing a prescribed course: The patient must finish the course to reduce the chance of surviving bacteria becoming resistant.AQA
Complications and risk: A serious illness that can be fatal if complications arise, such as pneumonia, encephalitis or ear infections, especially in malnourished children or those…AQA
Composition of blood plasma and urine: Blood plasma contains glucose, ions and urea, which are filtered into the initial filtrate, while ions and urea remain in the urine.AQA
Compound measure: A measure that combines two different quantities, for example distance per unit time or volume per unit time.AQA
compound measures: Quantities that quantify the speed of physical or biological processes per unit time, formed by dividing a measured quantity by elapsed time.OCR
Compound measures of rate: A measure found by dividing the volume of water taken up by the time taken, for example 12 cm³ ÷ 4 minutes = 3 cm³ per minute.AQA
compound units: Units such as grams per day or cubic centimetres per hour, used to express rate of decay.OCR
Concave (diverging) lens: A spectacle lens that spreads rays before they enter the eye so they focus on the retina, correcting short sight.AQA
Concentration gradient: The difference in concentration between two regions separated by a membrane; a larger difference gives a faster net rate because more particles move from the…AQA
Concentration gradients: If there is a higher concentration of a substance on one side of the membrane than the other, random movement produces a net transfer towards the lower…AQA
Condensation reaction: The reaction in which nucleotides join together between the phosphate of one nucleotide and the sugar of the next.AQA
Conditions for decay: Decay normally needs warmth, moisture, oxygen and decomposers, and if one or more of these is missing, body parts may survive and become fossils.AQA
Conditions for fossil formation: Conditions must usually be right, such as rapid burial, low oxygen, or preservation in ice, amber or acidic peat.AQA
Cone cells: Receptors sensitive to colour that need brighter light.AQA
Conflict between science and belief: The ideas were controversial because they challenged literal readings of religious accounts of creation.AQA
confounding variable: An uncontrolled factor, such as a rise in temperature from hot incandescent lamps, that affects the rate alongside the independent variable.OCR
confounding variables: Factors such as diet, smoking, or age that must be controlled by matching patient cohorts for age, sex, and health status.OCR
Consequences for health and treatment: Breathlessness, tiredness, dizziness, fainting and swelling caused by fluid retention can result, and severe cases may require treatment such as valve…AQA
Consequences of imbalance: If cells lose too much water the cytoplasm becomes concentrated and the cell may shrink; if they gain too much water the cell may swell and burst.AQA
Conservation: Cloning a rare species can increase numbers and provide a genetic backup that may protect the species from extinction.AQA
Conservation and sustainability: Recent measures such as nature reserves, legal protection of species, replanting trees, reducing pollution and recycling that aim to slow or stop the…AQA
Conservation methods: Controlling net size and introducing fishing quotas, which together aim to keep the rate of fishing below the rate at which the stock can replace itself.AQA
Consumers: Organisms that obtain their carbon and energy by eating producers or other consumers, so all food chains depend on the molecules synthesised by producers.AQA
Contact lenses: Hard and soft lenses that sit on the surface of the cornea to provide the correct refraction.AQA
Contaminants: Unwanted microorganisms that can grow on the medium and produce colonies not caused by the test organism, making results invalid.AQA
continuous physiological variables: Variables such as age or blood pressure that are represented by histograms with touching bars.OCR
continuous sampling: Withdrawing aliquots at fixed intervals, for example every 30 seconds, and adding them to reagent on a spotting tile to follow a process such as starch…AQA, OCR
Continuous transport pathways: The pores in the end walls create a continuous pathway along the tube, so cell sap can pass from one phloem cell to the next.AQA
continuous variation: A smooth numerical gradient across a continuous range, such as human height or body mass, which is polygenic and substantially modified by environmental…AQA, OCR
contraception: Techniques that prevent unwanted pregnancy through hormonal or non-hormonal mechanisms.OCR
Control: A sample such as starch solution without amylase, included to show that the blue-black colour is caused by starch.AQA
control disc: A disc soaked in sterile water, used to prove that the clear zone is caused by the test substance.AQA
Control measures: Measures such as sewage treatment, filters and safe disposal, chosen to match the source of the pollution.AQA
Control of cell activity: The role of DNA, which carries the instructions that control the characteristics and activities of the cell.AQA
Control of heart rate: The natural resting heart rate is controlled by a group of cells located in the right atrium that act as a pacemaker.AQA
Control of ripening: Ethene controls the rate and timing of ripening, so fruit can be stored and transported before it ripens.AQA
control of thermal variables: Water temperature is measured with a digital thermometer to confirm consistency across runs and monitor control.OCR
Control of variables and rate calculations: Keeping other variables such as volume of milk and starting pH the same, and calculating the rate of decay from the change in pH divided by the time taken.AQA
control tube for gas volume correction: A control tube containing boiled/dead seeds or glass beads of equal volume is included in the same water bath to account for thermal expansion.OCR
control variables: The volume and concentration of each substance, the bacterium, incubation temperature, and disc size, kept the same for a fair comparison.AQA
Control variables in investigations: Temperature is a control variable, while pH is the independent variable.AQA
Controlled conditions and optimum growth: A fermenter maintains optimum temperature, pH, oxygen and nutrient levels so that a single starter culture multiplies into a very large population.AQA
controlled variables: These include enzyme volume and concentration, substrate volume, temperature and pH, which are kept constant during the investigation.OCR
Controlling temperature: Reduces heat loss from the animal to the surroundings, so less food is respired to stay warm.AQA
convection current: A roaring blue Bunsen flame creates an upward current; working within about 20 cm of it prevents airborne microbes settling on open agar plates.OCR
convection currents: Upward currents created by working close to a Bunsen flame that carry airborne microbes away from open plates.OCR
Converting: Moving the decimal point until one non-zero digit remains on its left, then counting the moves: left gives a positive index, right gives a negative index.AQA
Convex (converging) lens: A spectacle lens that bends rays inward so they focus on the retina, correcting long sight.AQA
Cooperation of bile and lipase: Bile neutralises stomach acid and emulsifies fat, while lipase chemically digests fat into fatty acids and glycerol.AQA
Cooperation of tissues within organs: Each tissue contributes a different job, so the organ can perform a task that no single tissue could achieve alone.AQA
coordinate extraction: Accurately extracting coordinates from photosynthesis rate curves, and translating tabular values into plotted points on a coordinate grid.OCR
coordinated response: A unified response produced when integration within the brain or spinal cord coordinates multiple sensory inputs.OCR
Coordination: The central nervous system processes information and coordinates the response, allowing rapid reactions and more complex behaviours.AQA
Coordination between detection and response: Each mechanism is explained by linking the stimulus, the response and the resulting heat transfer, with responses coordinated as negative feedback restoring…AQA
Coordination centre: Processes the information during a negative feedback pathway.AQA
Coordination centres: Structures such as the brain, spinal cord and pancreas that receive and process information from receptors.AQA
Coordination of contraction: The impulse spreads through the atria, causing them to contract, and then reaches the ventricles so that they contract slightly later, maintaining one-way flow.AQA
Coordination of organs: Several organs work together in the digestive system to digest and absorb food.AQA
Coordinator: Such as the brain, spinal cord or pancreas, receives and processes the information.AQA
Core temperature: The body's internal temperature, which blood temperature reflects because blood circulates from the core.AQA
cork borer: Apparatus used to excise plant tissue cylinders, which are then trimmed to equal lengths on a ceramic tile using a scalpel.OCR
cornea: A transparent and curved front layer that refracts light strongly as it enters the eye.AQA
Coronary circulation: The coronary arteries supply oxygenated blood to the heart muscle itself.AQA
Coronary heart disease: A non-communicable disease in which atheroma builds up in the coronary artery wall, narrowing the lumen and reducing the flow of blood.AQA
corpus luteum: The ruptured follicle becomes this structure, secreting progesterone and oestrogen, which inhibit both pituitary hormones and maintain the uterine lining.AQA, OCR
Correct and consistent use: Effectiveness depends on correct and consistent use of the chosen method.AQA
Correlation: A statistical association that alone does not prove causation because other factors may be involved.AQA
Correlation and causation: A causal link is stronger when evidence shows a mechanism, a dose response and consistency across studies, so correlation is not proof of causation.AQA
correlation versus causation: Correlation establishes an association, but proving causation requires demonstrating an underlying biological mechanism.OCR
corrosive chemical isolation: Protecting invertebrates from direct contact with corrosive carbon dioxide absorbents such as soda lime pellets by a secure wire mesh barrier in respirometer…OCR
crenation: The shrivelling and shrinking of a cell when water moves out by osmosis and the cytoplasm loses volume.OCR
crop yield optimisation: Identifying the point of diminishing returns on fertiliser response graphs where yield plateaus, giving the optimum application rate that avoids financial…OCR
cross-sectional area calculation: Applying the formula A = πr² to determine the area in mm², after dividing the measured diameter by two to find the radius r.OCR
crown gall: The bacterium Agrobacterium tumefaciens transfers plasmid DNA into plant cells, inducing crown gall tumours.OCR
Current classification data: Data used for living organisms, including observable features, DNA base sequences, protein amino acid sequences and biochemical similarities.AQA
Cuttings: A simple method used by gardeners in which a shoot or piece of stem is cut from a parent plant and planted so that it grows into a new plant.AQA
Cycle regulation: Progesterone provides negative feedback on FSH and LH, and falling progesterone when no fertilisation occurs allows FSH to rise and restart the cycle.AQA
Cycling of matter: Water is recycled and its total amount is conserved, as the cycle continuously supplies fresh water to land organisms before water eventually returns to the…AQA
Cytokinesis: The stage of the cell cycle in which the cytoplasm and membranes divide to give two separate cells.AQA
Cytokinesis in animal and plant cells: In animal cells the cell membrane pinches inwards until the cell splits, while in plant cells a cell plate forms across the middle and develops into a new…AQA
Cytoplasm: A watery jelly where most chemical reactions of the cell happen.AQA

D

Darwin and Wallace: Independently formulated the theory of evolution by natural selection, leading to a joint scientific presentation in 1858 and Darwin's publication of On the…OCR
Data analysis and graph interpretation: Calculating percentage change in mass allows valid comparisons, and a graph shows positive values as water uptake, negative values as water loss and zero as…AQA
data extraction: Extracting and comparing quantitative values from tables and curves supports biological conclusions, quoting specific data pairs with units.OCR
Data handling skills: Identifying the axes, labels, units and keys of a chart, graph or table before reading any values, and extracting only the information asked for.AQA
data interpretation: Reading specific values with their units, identifying trends such as peaks and troughs, calculating changes over time, and describing relationships between…AQA, OCR
Data interpretation from tables and bar charts: Reading the numerical scale carefully and quoting specific concentrations with units to compare glucose, ions and urea before and after filtration.AQA
Data presentation and interpretation: Presenting results in a table and graph, then interpreting whether the factor affected reaction time.AQA
Data presentation and translation: Reading a value from a graph and writing it as a number, or plotting numerical data as a graph.AQA
Data recording and analysis: Recording measurements accurately and processing results to identify patterns, such as the effect of practice or a stimulant on reaction time.AQA
data translation: Moving information between numerical data tables and graphical representations, such as converting raw experimental readings into coordinates and plotting…OCR
Daughter cell formation: Two separate cells are produced, each receiving a full set of chromosomes and roughly half the cytoplasm and organelles.AQA
Dead cell layers and shedding bark: Layers of dead cells around stems, forming bark on trees, that create an outer barrier and eventually fall off, carrying pathogens away.AQA
Deamination: The liver removes the nitrogen-containing amino group from excess amino acids in this reaction.AQA
Decay: The breakdown of biological material by microorganisms such as bacteria and fungi.AQA
Decay and preservation: Soft tissue decays quickly due to bacterial action and is rarely replaced by minerals, so it seldom fossilises, while hard parts resist decay and are much…AQA
Decomposers: Bacteria and microscopic fungi that break down dead plant matter, animal carcasses and excreted waste, driving nutrient recycling in ecosystems.AQA, OCR
Decomposition: The breaking down of dead organisms, fallen leaves and animal waste by microorganisms such as bacteria and fungi, which digest complex organic compounds and…AQA
Decomposition and decay: Decomposers break down dead organisms and waste products, releasing mineral ions and carbon dioxide back to the environment.AQA
Decomposition and respiration: Microorganisms break down organic matter in peat, and respiration releases carbon dioxide.AQA
decomposition calculation: Calculating the mean rate of decay by dividing change in mass, volume, or pH by the time taken.OCR
decomposition factors: Temperature affects kinetic energy and enzyme-substrate collisions up to an optimum, water content is vital for metabolism, enzyme secretion and nutrient…OCR
Defence and clotting: White blood cells contain a nucleus, which supports defence functions such as engulfing pathogens or producing antibodies, while platelets are small cell…AQA
degenerate: Several triplets can code for the same amino acid, because there are 64 possible triplets but only about 20 amino acids.AQA
Degenerate genetic code: The code is degenerate, so a base substitution may still code for the same amino acid and leave the protein unchanged.AQA
dehydration: Heavy sweating causes significant water loss, reducing blood water potential, which osmoreceptors detect and which triggers thirst.OCR
Demand for food: The need for food in total, which rises as an increasing birth rate raises the population size.AQA
denaturation: Above the optimum temperature, thermal agitation breaks hydrogen bonds, damaging enzyme active sites and permanently halting photosynthesis.AQA, OCR
Denaturation as a permanent change: Extreme conditions denature enzymes by altering the active site, so the substrate no longer fits and the change is permanent.AQA
Denature: The irreversible change in the specific three-dimensional shape of an enzyme, particularly the active site, due to factors like high temperature or extreme pH.OCR
deoxyribose: Each sugar in the backbone is deoxyribose, and attached to each sugar is one of four bases.AQA
dependent variable: The variable that is measured, such as length or direction of shoot and root growth.AQA, OCR
Destroying removed leaves: Disposing of removed leaves, for example by burning or binning them rather than adding them to compost, so spores do not return to the rose.AQA
Detection and identification of plant disease: Working out the cause of a plant's disease once it shows symptoms, before choosing a treatment.AQA
Detection of plant disease from visible signs: Using visible signs to detect a problem before identifying the cause; these signs indicate disease but do not by themselves identify the pathogen.AQA
Development: The production of many cells by mitosis to form specialised tissues and organs.AQA
development and growth: Division of embryonic stem cells to produce all specialised cell types, driving tissue morphogenesis and organ development.OCR
Development of evolutionary theory: The joint writings presented natural selection to the scientific community, and the book made the theory widely known.AQA
Development of genetics: Our understanding developed in stages, from Mendel's 'units' to chromosomes, then DNA structure and gene function, leading to gene theory.AQA
Development of scientific theories: Scientific theories are revised and refined as new evidence is collected, rather than remaining fixed, so the current theory of speciation is stronger because…AQA
Diabetes: A condition in which some cases involve cells in the pancreas that no longer produce enough insulin.AQA
diabetes mellitus: A metabolic disorder characterised by an inability to control blood glucose levels.OCR
Diagnosis of infection: A blood test, not the symptoms alone, is needed to confirm HIV infection.AQA
Dialysis: A machine treatment that filters the blood outside the body when the kidneys fail.AQA
Diet and nutrition: A balanced diet is needed for good health, while a poor diet can cause malnutrition or obesity and can also affect mental health.AQA
Diet-dependent classification of consumers: The same species can occupy different trophic levels in different food chains if its diet differs.AQA
dietary transitions: Dietary shifts toward meat and dairy in wealthier populations, requiring substantial grain and water to feed livestock.OCR
differential staining and contrast: Applying stains such as crystal violet or methylene blue to provide contrast against cell walls and cytoplasm of colourless microbial cells.OCR
differential survival: Higher survival rates and reproductive success enjoyed by individuals possessing phenotypic characteristics best suited to their environment.OCR
Differential survival and reproduction: Better-suited individuals are more likely to survive, and because they survive longer they are more likely to reproduce and pass their alleles on.AQA
Differentiation: The process in which a cell switches on particular genes so it develops the right shape, organelles and proteins for its job.AQA
Diffusion: The net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient, and it is passive…AQA, OCR
Diffusion and concentration gradients: A passive process in which particles move from a region of higher concentration to a region of lower concentration down a concentration gradient.AQA
Diffusion and metabolic demand: The rate of diffusion must match the organism's metabolic demand for the transport to be sufficient to meet the needs of the organism.AQA
Diffusion and organism size: Diffusion across the outer surface alone would not supply enough oxygen and nutrients to every cell, nor remove enough carbon dioxide and other waste…AQA
diffusion distances: The distance from the exterior to interior tissues becomes far too great for diffusion alone to supply oxygen or remove toxic urea.OCR
Digestion and absorption: Digestive enzymes convert food into small soluble molecules that can be absorbed through the wall of the small intestine into the bloodstream.AQA
Digestion as a supply of substrates: Digestive enzymes break down large food molecules into small soluble products that can be absorbed and used in metabolism.AQA
Digestive enzymes and their substrates: Amylase acts on starch, protease acts on proteins and lipase acts on lipids.AQA
digital stopwatch: Device used to time reaction duration, with times recorded to the nearest second to reflect human reaction time limitations.OCR
diploid: Having two complete sets of chromosomes, or chromosomes in pairs, such as 46 chromosomes in human somatic cells.OCR
Diploid and haploid: Ordinary human body cells are diploid, containing 23 pairs or 46 chromosomes, while gametes are haploid, containing 23 single chromosomes.AQA
Diploid and haploid cells: Body cells are diploid, containing two copies of each chromosome, while gametes are haploid and carry one chromosome from each pair.AQA
Diploid number: The normal number of chromosomes for the species, restored when two haploid gametes fuse.AQA
Direct contact: Transfer by touching an infected organism or its body fluids, or transfer between plant leaves.AQA
direct proportion: The expected number of individuals exhibiting a given trait scales in direct proportion with total sample size.AQA, OCR
Direct secretion into the bloodstream: Endocrine glands secrete hormones directly into the bloodstream, so they can be carried to every part of the body.AQA
disc diffusion antimicrobial assay: A method in which filter paper discs impregnated with known concentrations of test substances are placed onto a sterile bacterial lawn on nutrient agar to…OCR
Discolouration: A change from the normal colour, such as yellowing of leaves.AQA
discontinuous variation: Distinct, non-overlapping categories with no intermediate states, such as human ABO blood groups or eye colour, typically controlled by a single gene with…AQA, OCR
Discovery and development of drugs: Drugs can be discovered by observing natural sources, then developed and tested before medical use.AQA
Discovery of sub-cellular structures: Electron microscopy revealed organelles that light microscopy could not resolve, including ribosomes, endoplasmic reticulum, Golgi apparatus and lysosomes.AQA
disease: A physiological or psychological condition that impairs normal bodily or cellular functioning, producing characteristic clinical symptoms and signs.OCR
Disease control: Control relies on removing infected plants, disinfecting tools, and using resistant varieties, because antibiotics are useless against a virus.AQA
Disease incidence: The number of new cases in a population over a period.AQA
disease prevalence: Figures that can be converted into percentages or rates per 100,000 population.OCR
Disease resistance: Crop plants can be genetically engineered to resist diseases, which may reduce crop losses and improve yield.AQA
distance and light intensity measurement: Distance from the light source to the plant is measured in metres using a metre ruler placed at bench level.OCR
distance calculations: Calculate d² first, then take the reciprocal 1 / d², and state that the value is relative or in arbitrary units.OCR
Distribution along environmental gradients: Placing quadrats along a transect line across the habitat and measuring the chosen factor, such as light intensity or soil moisture, at each point to see…AQA
Distribution of species: Where organisms of a species are found within an ecosystem.AQA
division of labour: Different cells contribute to different life processes, which differentiation enables among cells.AQA, OCR
DNA: A chemical, standing for deoxyribonucleic acid, that carries the instructions controlling the characteristics and activities of the cell.AQA, OCR
DNA as a double helix: Two chains of sugar and phosphate groups, with bases sticking out, twist around each other.AQA
DNA evidence for human migration: Comparing DNA between populations shows how humans moved around the world over thousands of years, with mitochondrial DNA and Y-chromosome markers acting like…AQA
DNA loop: The main genetic material of a prokaryotic cell, which is a single DNA loop that lies free in the cytoplasm rather than inside a nucleus.AQA
DNA outside the nucleus: The genome includes DNA in mitochondria and, in plant cells, in chloroplasts, as well as the DNA in the chromosomes.AQA
DNA replication: Occurs during interphase, when the genetic material is doubled so each chromosome becomes two identical copies.AQA, OCR
DNA replication before division: Before division begins, the DNA is replicated so each chromosome becomes two identical chromatids, giving copies of the genetic information.AQA
DNA sequencing: Sequencing of DNA bases that, with protein analysis, allows precise phylogenetic mapping and provides objective evidence of evolutionary relationships.OCR
DNA structure and function: In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out.AQA
DNA testing and PCR: Laboratory detection of the DNA from the disease causing organism, using DNA extraction, PCR amplification and sequencing to identify the pathogen definitively.OCR
Domestication of plants and animals: Humans first bred food crops from wild plants and domesticated animals thousands of years ago.AQA
Dominant allele: An allele that is always expressed when present, so in mice the dominant allele for fur colour ensures that trait is expressed even if a recessive allele is…AQA
dominant and recessive alleles: In crosses involving these, homozygous dominant crossed with homozygous recessive gives heterozygous offspring expressing the dominant phenotype.OCR
Donor organ availability: Donor organs are scarce, so patients may wait a long time and some do not receive one.AQA
Dose: The amount tested to find one that gives a useful effect with acceptable side effects, often by trying a range of doses.AQA
Dose and timing: Must be managed alongside diet and exercise to avoid blood glucose becoming too high or too low.AQA
double circulatory system: A system in which blood passes through the heart twice for each complete circuit of the body.AQA, OCR
double helix: The arrangement in which the bases project from the backbone and form hydrogen bonds with bases on the opposite strand produces the double helix.AQA, OCR
Double helix structure: The shape formed when the two strands twist around a shared axis, looking like a twisted ladder.AQA
double-blind placebo trials: Large-scale trials comparing the drug against a placebo, where neither patients nor doctors know who receives the active drug, eliminating psychological and…OCR
Double-stranded structure of DNA: DNA consists of two complementary strands held together by hydrogen bonds between bases.AQA
Drug development and modification: Chemists modify the molecule to improve potency, reduce side effects or make administration easier.AQA
Drug discovery: Potential drugs are identified from plant or microorganism extracts, or designed and synthesised in the laboratory.AQA
Drug discovery and development: Screening plants and microorganisms for useful compounds, with many modern medicines derived from or based on natural compounds.AQA
Dry mass: The mass of living material measured without water, usually in g m⁻² or kg m⁻², since water content varies and is not useful for comparing trophic levels.AQA
Ductless versus ducted secretion: Endocrine glands are ductless, whereas exocrine glands release substances through ducts, such as salivary glands.AQA
Duration and reversibility of methods: Understanding the variety means knowing the route, duration and mechanism of each option, such as a skin patch, a slow-release implant or a permanent surgical…AQA

E

Early life: Many early forms of life were soft-bodied, which means that they have left few traces behind.AQA
Early-stage gene transfer and development: Genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired…AQA
ecological data: Complex information from field investigations and environmental monitoring, presented in charts, food web matrices and line graphs.OCR
Economic and practical priorities: Selective breeding is driven by human priorities, which may be economic, agricultural, aesthetic, or behavioural.AQA
Economic importance of microorganisms: Fermentation in yeast cells is used in the manufacture of bread and alcoholic drinks.AQA
Economic issues: Points such as the cost of embryo screening, the cost of lifelong treatment for a disorder, and who bears those costs.AQA
Ecosystem: The interaction of a community of living organisms with the non-living parts of their environment.AQA
Ecosystem comparison: When comparing two areas, count or estimate the number of species present rather than simply the total number of organisms.AQA
ecosystem definition: The complete, self-sustaining functional unit formed by the living community of organisms interacting with all the non-living physical and chemical abiotic…OCR
Ecosystem stability: The ability of an ecosystem to keep functioning when conditions change, resisting or recovering from change such as disease, drought or the arrival of a new…AQA
ecotourism: Generates valuable revenue for local communities, providing strong financial incentives to protect pristine habitats rather than exploiting them for…OCR
Effect of faulty valves on circulation: A faulty valve may fail to close completely, allowing blood to leak backwards, or may be narrowed, restricting forward flow.AQA
Effect of temperature and pH on enzyme activity: Enzyme activity depends on temperature and pH, with an optimum for each enzyme, and conditions away from the optimum reduce enzyme activity.AQA
Effect on protein: Most mutations do not alter the protein, or alter it only slightly, so its appearance or function is not changed.AQA
Effectiveness, side effects and infection risk: Hormonal methods are highly effective when used correctly but can cause side effects and do not protect against sexually transmitted infections, whereas…AQA
Effector: A muscle or gland that responds by contracting or secreting, producing the reflex action.AQA
Effectors: Muscles that contract or glands that secrete chemical substances, which may include hormones but also other secretions such as enzymes or sweat.AQA, OCR
Effectors and response: Muscles, which contract, or glands, which secrete chemicals, respond to impulses carried by motor neurones.AQA
Effects of disease: Damage to leaf tissue, yellowing and early leaf drop, which reduce the total leaf area available for photosynthesis.AQA
Effects of mutations on phenotype: Most mutations have no effect on the phenotype, some influence the phenotype and very few determine the phenotype.AQA
Efficacy: The ability of the drug to produce the intended therapeutic effect, such as lowering blood pressure or killing bacteria.AQA
efficacy evaluation: Balancing theoretical effectiveness, user reliability, potential side effects, and protection against sexually transmitted infections when assessing…OCR
Efficiency of biomass transfer: Only approximately 10 % of the biomass from each trophic level is transferred to the level above it, and this figure is an approximation that varies with the…AQA
Efficiency of food production: The proportion of feed energy converted into useful biomass, which is raised when less energy is transferred to the environment.AQA
egestion: The loss of ingested material that is not absorbed and is passed out as faeces, so it is not available to the next trophic level.AQA, OCR
Electrical impulses: Information from receptors passes along cells (neurones) as these to the central nervous system.AQA
Electrical signalling in the heart: A group of specialised cells in the wall of the right atrium generates electrical impulses, and the resulting wave of electrical activity coordinates…AQA
Electrical stimulation: Electrical impulses delivered to the heart muscle that trigger contraction.AQA
Electrically stimulating different parts of the brain: During surgery this can trigger responses, such as movement or sensations, showing what a region does.AQA
Electron microscope: Uses a beam of electrons with a far shorter wavelength, giving resolution down to about 0.2 nm and much higher magnification.AQA
Electron microscopes: Instruments that use a beam of electrons, which has a much shorter wavelength than light, giving higher resolution and allowing greater useful magnification.AQA
electronic balance: Apparatus used to record masses to 0.01 g.OCR
embryo: The fertilised egg divides by mitosis to form this, which is cultured in a laboratory until it is a tiny ball of cells.AQA
Embryo development: Repeated mitotic divisions cause the overall number of cells to increase, forming an embryo.AQA
embryonic stem cells: Cells isolated from early blastocysts that are pluripotent and carry ethical considerations or immune rejection risks.OCR
Emulsification: The physical breakdown of fat into small droplets, which increases the surface area.AQA
emulsion test: A test using ethanol and water that identifies lipids by forming a white milky emulsion.OCR
Emulsions in digestion: The droplets remain fat but are spread through the watery contents of the small intestine, forming an emulsion.AQA
end point: The stage of starch digestion when the sampled mixture no longer turns iodine blue-black and remains yellow-brown.AQA, OCR
Endocrine cascades: Hormones from the pituitary travel in the blood to other endocrine glands and stimulate those glands to secrete their own hormones.AQA
endocrine glands: Ductless glands that synthesise and secrete chemical messengers called hormones directly into blood capillaries.AQA, OCR
endothermic reaction: A reaction that absorbs energy from its environmental surroundings, which is how photosynthesis is categorized chemically.OCR
Energy and biomass loss in food chains: Energy is lost between trophic levels through respiration, movement, excretion and uneaten material, so biomass always decreases at each successive level.AQA
Energy and time efficiency: No time or energy is spent finding a mate, producing gametes or attracting pollinators, so more resources go into growth and offspring.AQA
energy dissipation: Roughly 90 percent of biomass is dissipated at each level via cellular respiration, movement, egestion, and excretion.OCR
Energy from respiration for active transport: Active transport uses energy from respiration, and the large number of mitochondria in root hair cells supplies the energy needed.AQA
Energy loss in ecosystems: Biomass and energy are lost at each transfer, mainly through respiration, movement, excretion and heat, so less is available at higher trophic levels.AQA
Energy loss in food chains: Much of the glucose taken in by an organism is respired, releasing carbon dioxide and water, which helps explain why biomass and energy decrease between…AQA
energy release: The release of chemical potential energy from organic molecules, primarily glucose, to synthesize ATP.OCR
Energy requirements in cells: Because substances are moved against the gradient, active transport requires energy from respiration.AQA
Energy transfer: Arrows in a food chain show the transfer of biomass and energy, and energy is lost at each transfer through respiration, movement, excretion and heat.AQA, OCR
Energy transfer in cells: Energy is released for cells when some glucose is used in respiration, and synthesis of new biological molecules requires this energy.AQA
Energy transfer in food chains: The pathway from feed to animal biomass to useful food product, with losses to the environment at each stage.AQA
Enucleation: The removal of the egg cell's own nucleus, leaving the cytoplasm and cell membrane intact.AQA
Environmental causes: Differences due to the conditions in which individuals have developed, such as diet, exercise, temperature or light.AQA
Environmental change: A change that can make conditions in an ecosystem more or less suitable, so species may spread into new areas, become restricted to smaller areas, or…AQA, OCR
Environmental conditions and disease: Damp, humid conditions favour spore germination and infection, so fungal diseases often spread quickly in warm, humid weather.AQA
environmental monitoring: Assessing compliance with ecological safety benchmarks, for example where air quality regulations specify that the 95th percentile of daily sulfur dioxide…OCR
Enzyme: A protein that functions as a biological catalyst, speeding up reactions without being used up.AQA
Enzyme action: A change in shape can change the protein's function, for example an enzyme's active site may no longer fit its substrate.AQA
enzyme active sites: Folding determines protein function, such as the precise shape of an enzyme's active site.OCR
Enzyme activity: Temperature is linked to its role as affecting enzymes.AQA
Enzyme activity and temperature: Microorganisms release enzymes that digest the milk's lactose into acids, and very high temperatures may kill or denature these enzymes so decay can slow again.AQA
enzyme denaturation: Altered active sites caused by deviations such as high temperatures, which halts respiration and metabolism.OCR
enzyme investigations: These track the rate of substrate use or product formation under controlled conditions, using gas collection or timed sampling.OCR
enzyme kinetics: Warming increases kinetic energy and enzyme-substrate collisions, raising the rate up to an optimum, above which microbial enzymes denature and decay slows…OCR
Enzyme optimum: The temperature at which enzymes work best, kept stable by a stable temperature.AQA
Enzyme specificity: The idea that an enzyme's active site is complementary to its substrate, so amylase acts on starch but not on proteins or lipids.AQA
Enzyme stability: Heat-stable enzymes are an adaptation matched to extreme conditions, meeting the challenge of enzyme denaturation.AQA
Enzyme structure and active site specificity: Enzymes are proteins that catalyse metabolic reactions, and their activity depends on the active site fitting the substrate.AQA
Enzyme structure and function: A mutation can change the amino acid sequence and therefore the shape of a protein, so the shape of an enzyme's active site may change and the substrate no…AQA
Enzyme-controlled reactions: Reactions that each need a specific enzyme, so temperature and pH affect metabolism.AQA
Enzymes and hormones: Proteins that do their job by folding to create a specific active site complementary to a particular substrate, or by relying on their specific shape to bind…AQA
epidemiological rates: Standardized rates converted from raw medical case numbers, such as cases per 100,000 people or percentages.OCR
epidemiologists: Scientists who track transmission dynamics by quantifying confirmed cases and estimating true prevalence across populations using representative sampling.OCR
Epidermal tissue: A thin, flat protective covering; in leaves it is covered by a waxy cuticle that reduces water loss by evaporation.AQA
equilibration period: A period, for example 5 minutes, allowed at each new light intensity or distance before collecting data.OCR
erythrocyte adaptations: A biconcave disc shape, lack of a nucleus, and a small size with flexible membrane enabling single-file transit through narrow capillaries.OCR
estimation: A rapid, sensible approximation of cell dimensions and populations used when exact measurements are impractical, and to verify whether calculated answers are…AQA, OCR
ethanol: A highly flammable liquid used to dissolve and extract chlorophyll from the leaf so that subsequent colour changes are clearly visible.OCR
ethene gas: A unique gaseous plant hormone that acts as a potent regulator of fruit ripening, promoting colour changes and tissue softening by activating cellulase enzymes.OCR
Ethical and religious objections: Reasons some people object to genetic engineering on ethical, religious or environmental grounds, which are valid viewpoints.AQA
ethical considerations: Using human embryos raises serious ethical controversies regarding the destruction of potential human life.OCR
Ethical issues: Points such as the moral status of embryos, the discarding of affected embryos, and concerns about selecting embryos for particular characteristics.AQA
ethical treatment of invertebrates: Transferring invertebrates gently with a soft paintbrush or specimen spoon to avoid mechanical trauma, and returning them to their natural damp habitat…OCR
Ethical, legal and social implications: The benefits must be weighed against issues such as privacy of genetic data, insurance and employment discrimination, cost, and unequal access to testing.AQA
Ethics: Concerns raised because obtaining embryonic stem cells involves destroying early embryos.AQA
Ethics of animal research: Animal testing raises ethical issues, so it is regulated and carried out only when necessary.AQA
Ethics of embryo use: The embryo is not allowed to develop into a baby; it is used as a source of stem cells for treatment.AQA
Ethics of genetic information: Questions about privacy, consent, insurance and fair access raised by genetic information, with concerns such as discrimination if information is shared.AQA
Ethics of stem cell research: Ethical issues around the use of embryos as a stem cell source, which a balanced answer should present alongside potential benefit.AQA
Eukaryotic: Describes cells whose genetic material, DNA, is enclosed in a nucleus bounded by its own membrane.AQA
Eukaryotic DNA: Genetic material that is enclosed in a nucleus, which separates the DNA from the cytoplasm.AQA
Eutrophication: Fertiliser washed from fields into a lake causes algae to grow rapidly, then decompose, and the oxygen concentration falls so fish and other animals die.AQA
evaluation: Weighing benefits against risks and limitations for a particular patient, not simply listing treatments.AQA
Evaporation and condensation: Energy from the Sun causes evaporation of water from seas, lakes, rivers and soil, while water vapour cools and condenses to form clouds.AQA
Evidence and bias: The fossils we do find are biased towards organisms with hard parts, so a soft-bodied worm is far less likely to leave a fossil than a shelled mollusc living…AQA
Evidence and causation: Correlation shows an association, not proof that one variable causes the other, because other factors may be involved.AQA
Evidence and genetics: Modern genetics does not support Lamarck's idea because changes acquired during life generally do not alter the inherited material passed to offspring.AQA
Evidence and uncertainty in science: Some links between risk factors and diseases remain uncertain because the exact biological steps may be complex or not established.AQA
Evidence before human trials: Results from preclinical testing help decide whether a drug is promising and safe enough to move into clinical trials with human volunteers.AQA
Evidence for evolution: Fossils show long-term change and antibiotic resistance shows natural selection in action, so the theory of evolution by natural selection is well supported.AQA, OCR
Evidence-based classification: Organisms are grouped using evidence such as internal structures and biochemical data, and new models of classification are proposed as this evidence becomes…AQA
Evidence-based evaluation: A balanced evaluation that weighs benefits against risks and recognises that decisions involve both evidence and values.AQA
Evidence-based evaluation of future benefits: A balanced answer states a medical use, explains how the genome sequence enables it, and notes a limitation or ethical concern.AQA
Evidence-based explanation: An explanation that uses numerical evidence from the resource, quoting data to support each point made.AQA
Evidence-based treatment choices: Zone measurements are used as evidence when discussing which antibiotic might be chosen for a bacterial infection.AQA
Evolution: A change in the inherited characteristics of a population over time through a process of natural selection, which may result in the formation of a new species.AQA
Evolution by natural selection: This process repeated over many generations can lead to evolution of the population.AQA
Evolution of populations: The population of the resistant strain rises because selection favours resistant individuals, so resistant bacteria become more common.AQA
evolutionary change: A change in the inherited characteristics of a population over time, through a process of natural selection, which may result in the formation of new species.OCR
evolutionary relatedness: Shared ancestry reflected in natural classification systems, with greater sequence homology indicating more recent common ancestors.OCR
Evolutionary relationships: Relationships between organisms that the three-domain model reflects better than grouping by appearance alone, as revealed by molecular evidence.AQA
Evolutionary tree: A branching diagram showing how scientists currently believe organisms are related through common ancestors.AQA
Exchange surfaces: Specialised surfaces, such as the alveoli in lungs or villi in the small intestine, that increase the surface area and shorten the diffusion path.AQA, OCR
Exchange surfaces in animals: The small intestine, lungs and fish gills are adapted with thin walls, a short diffusion path and a blood supply for exchanging materials.AQA
Exchange surfaces in plants: Roots have root hair cells for uptake of water and mineral ions, while leaves have a thin lamina, stomata and internal air spaces for gas exchange.AQA
excretion: Urea is removed in urine by the kidneys, which excretes the nitrogen safely and helps maintain nitrogen balance in the body.AQA, OCR
Excretion and homeostasis: The kidneys are the main organ for controlling water, ion and urea balance, adjusting the volume and concentration of urine to help maintain balance.AQA
Excretion of water, ions and urea: Water leaves the body via the lungs during exhalation, while water, ions, and urea are lost through the skin in sweat.AQA
Exercise regime: Regular exercise increases the use of glucose by muscles during activity and can improve the sensitivity of body cells to insulin.AQA
exothermic reaction: Cellular respiration is classified chemically as this because the total bond energy of the products is lower than that of the reactants.OCR
Exothermic reactions: Reactions in which the energy released when bonds form in the products is greater than the energy needed to break bonds in the reactants, so energy is…AQA
Experimental design and control variables: Planning a hypothesis, identifying the independent variable and controlling relevant variables such as the same hand, same partner and same starting position.AQA
Explaining how a test or treatment produces a result: Linking the binding event to the observable result, such as a colour change or a line appearing.AQA
Exponential population growth: Population size after n divisions can be calculated as 2ⁿ, or by repeated doubling, so numbers double each generation under ideal conditions.AQA
Expression of inserted genes: The plant makes the protein coded for by the new gene, which is present in the plant's cells.AQA
External digestion by microorganisms: Secreting digestive enzymes into the surrounding environment so that complex organic molecules are broken down into simpler soluble substances outside the…AQA
Extracellular digestion: Enzymes are secreted onto the food outside the cell, breaking large insoluble molecules into small soluble molecules.AQA
extracellular enzymes: Digestive enzymes secreted externally onto dead organic matter that hydrolyse complex insoluble polymers into soluble monomers.OCR
Extract information: Read the axes, units, labels and key of a chart, graph or table carefully, then identify the relevant data points.AQA
Extreme conditions and enzyme stability: Bacteria in deep sea vents must keep their enzymes and cell structures working despite temperatures that would denature enzymes in most organisms, and their…AQA
Extreme environments: Environments that are very extreme, such as at high temperature, pressure, or salt concentration, with conditions that would kill most organisms.AQA
Extreme-environment archaea: Primitive bacteria-like organisms usually living in extreme environments, whose cell walls and biochemistry differ from true bacteria.AQA
Extremophiles: Organisms adapted to survive and reproduce in environments where conditions are extreme, such as very high temperature, pressure, salt concentration or acidity.AQA
eye protection: Safety wear required during the procedure, along with handling tubes with tongs and avoiding all open flames near ethanol vapours.OCR
eye structure: The main structures of the eye include the cornea, iris, pupil, lens, retina, optic nerve, ciliary body and suspensory ligaments.OCR
eyepiece graticule calibration: Calibrating the eyepiece graticule against a stage micrometer gives the true distance per graticule division at each magnification.OCR

F

Factor interactions: Increasing a non-limiting factor has little or no effect on the rate until the limiting factor is relieved.AQA
Factors affecting health: Diet, stress and life situations may have a profound effect on both physical and mental health, and these factors often interact.AQA
Fair comparison: Use the same time interval or calculate a rate for each condition rather than comparing raw totals measured over different times.AQA
Fair comparison of experimental samples: Using percentage change to compare samples of different starting masses.AQA
Fair testing and validity: If temperature changes, the time taken for starch to be digested would not be a fair comparison between pH values.AQA
Family tree: A diagram using symbols to show phenotypes across generations, which can be used to deduce genotypes.AQA
Fate of incident light: The rest is reflected, transmitted through leaves, absorbed by non-photosynthetic parts, or has wavelengths not used by chlorophyll.AQA
Fatty deposits and cholesterol: Fatty material, mainly cholesterol, builds up in layers inside the walls of the coronary arteries, narrowing them.AQA
Faulty valve: A heart valve that may become faulty, preventing the valve from opening fully, or the heart valve might develop a leak.AQA
Favourable conditions and environmental stability: Many identical offspring can be produced when conditions are favourable, but this is risky if the environment changes.AQA
Feedback control: Where feedback inhibits or stimulates secretion, such as progesterone inhibiting FSH and LH and high oestrogen stimulating LH.AQA
Fermentation: Anaerobic respiration in yeast cells, which has economic importance in the manufacture of bread and alcoholic drinks.AQA, OCR
fertile offspring: Offspring that organisms can breed together to produce, the inability to do so being the crucial criterion for speciation.OCR
Fertilisation: The fusion of two gametes, usually one from each parent, which restores the normal number of chromosomes.AQA
Fertilisation outside the body: Sperm from the father is added to the collected eggs so that fertilisation can occur outside the body.AQA
fertilisation probability: At every fertilisation there is a 50% probability of a male or female child, an equal 1 to 1 ratio.OCR
fertilisers: Chemical fertilisers replace soil minerals to boost vegetative growth.OCR
Fertility drug: A treatment containing FSH and LH given to a woman whose own FSH level is too low, stimulating eggs to mature in the ovary and triggering ovulation.AQA
fertility drugs: Contain follicle-stimulating hormone and are administered to stimulate the maturation and release of viable eggs in women who do not ovulate naturally.OCR
Fever: A general response to infection as the body raises its temperature, caused by the bacterial infection and its toxins.AQA
field diagnosis: Diagnosis by observation and microscopy, inspecting crops for macroscopic symptoms and examining tissue smears with portable light microscopes.OCR
Field evidence and biogeography: Observations from fieldwork, such as closely related species living in nearby but separate areas and species suited to local conditions, which contributed to…AQA
Field margins and hedgerows: Reintroduced in monoculture farmland to increase habitat variety, providing food and shelter for wildlife and connecting fragmented habitats.AQA
field of view: The circular area seen under a light microscope, whose diameter can be measured using a stage micrometer or clear graticule.OCR
fight-or-flight: The response triggered by adrenaline during stress or fear, raising heart rate, dilating bronchioles, and diverting blood to muscles.OCR
Filtration: The process in the kidneys that forces small molecules from the blood into the kidney tubule, while blood cells and large proteins do not pass through.AQA
First trophic level: The position occupied by producers in every food chain because they do not need to eat other organisms to obtain carbon.AQA
Fish stocks: Populations of fish that are harvested for food, and whose numbers are declining in the oceans.AQA
Fishing quotas: A limit on the number or mass of fish that can be caught from a particular stock in a given period, so the breeding population remains large enough to…AQA
Flagella: Structures of bacteria that rotate to move the cell.Pearson Edexcel
flaming: Heating metal inoculating loops in a roaring blue Bunsen burner until red hot to incinerate contaminating microorganisms.OCR
Follicle: The structure in the ovary in which an egg matures.AQA
Follicle stimulating hormone: Released by the pituitary gland to stimulate an egg follicle to mature within an ovary.AQA, OCR
Follicle stimulating hormone (FSH): Causes maturation of an egg in the ovary, causing an egg to mature inside a follicle.AQA
Food and shelter provision: Roles that several species can carry out, so that if one species declines others can still provide food or shelter and the ecosystem continues to function.AQA
Food chain: A simple diagram that traces a single pathway of energy transfer and shows a feeding relationship.AQA
food chain length: Limited to four or five trophic levels because insufficient biomass and energy remain to support a viable breeding population of higher predators.OCR
Food chains: A food chain shows the direction of energy transfer between organisms, with each arrow pointing from the organism being eaten to the organism that eats it.AQA, Pearson Edexcel
Food chains and interdependence: The feeding links between organisms, which can be disrupted when insect populations that depend on wild flowers decline.AQA
Food industry applications: In the food industry, ethene is applied to unripe fruit during storage and transport so that ripening occurs at a controlled time, often just before sale.AQA
Food preservation: Refrigerating, drying, salting or vacuum-packing food to preserve it, explained by controlling the factors that affect decay.AQA
Food production and selective breeding: Selective breeding of crops and livestock can raise yield or quality, increasing food production.AQA
food production data: Information taken from charts, graphs and tables about agricultural and food production, from which numerical values must be extracted accurately with correct…OCR
Food safety: Concerns food being safe to eat, not whether enough is available.AQA
Food security: Having reliable access to enough safe, nutritious food, which is lowered when less food is produced and food becomes less affordable.AQA, OCR
Food security and agriculture: Cloning a crop plant with a special feature, such as disease resistance, produces many identical plants for farmers, giving a reliable crop.AQA
Food supply: Food production or imports, which must increase at the same rate as the population for food per person not to fall.AQA
food web: A set of chains in which a secondary consumer may eat several different herbivores, so it can appear in more than one chain.AQA
Food webs and cascading effects: Effects can spread through a food web as a cascade rather than staying with one pair of species.AQA
Food webs and energy transfer: Feeding links in which energy is transferred from producers to consumers, and a consumer depends on its prey.AQA
Formation of new species: Groups become so genetically different that they cannot interbreed to produce fertile offspring, which means they are now separate species.AQA
Fossil data: Data used for extinct organisms, such as the age, structure and anatomy of fossilised remains, and increasingly any preserved biomolecules.AQA
Fossil record: Chronological evidence showing structural anatomical changes over millions of years, documenting transitions in anatomy over evolutionary time.AQA, OCR
Fossil record gaps: The further back in time we look, the fewer fossils we find, creating gaps in the fossil record.AQA
Four bases attached to sugar: Attached to the sugar is one base, and there are four possible bases: adenine, cytosine, guanine and thymine.AQA
fractions and percentages: Used to model energy transfers, nutrient cycles and community structures, converting fractional proportions into percentages and decimals to evaluate…OCR
Frequency table: A table that records how often each category or value occurs.AQA
frequency tables: Organise clinical observations into discrete or continuous categories, grouping clinical health data into appropriate class intervals.OCR
Fresh water supply and drainage: The cycle continuously supplies fresh water to land organisms before water eventually returns to the seas, with water on land draining through soil and rock…AQA
From genotype to phenotype: A different protein synthesised by that gene may affect the phenotype.AQA
Fruit quality: Crop plants can be genetically engineered to produce bigger or better fruits, which may mean increased size, improved quality, taste or nutritional value.AQA
FSH and LH: Hormones given together to the mother to stimulate the maturation of several eggs in the ovaries.AQA
FSH and LH as pituitary hormones: Hormones produced by the pituitary gland that stimulate the maturation of follicles in the ovaries and trigger ovulation.AQA
Functional adaptations: Internal physiological or metabolic processes, such as producing concentrated urine or reducing metabolic rate during dormancy.AQA
Fungal life cycles: Many fungi use both methods, so the life cycle can include an asexual phase and a sexual phase.AQA
Fungi: Organisms that may be single-celled or multicellular and can grow on and penetrate host tissue.AQA
Fungicides: Chemicals applied to kill or inhibit the rose black spot fungus growing in the plant tissue.AQA
Fusarium: A filamentous fungus that can be grown industrially and cultured to produce mycoprotein.AQA

G

Gall bladder: A small muscular sac under the liver that stores bile and releases it into the small intestine.AQA
Gamete: A sex cell, such as a sperm or egg, with a haploid number of chromosomes.AQA
Gamete collection and laboratory techniques: Eggs are collected from the mother, usually by a fine needle guided by ultrasound, and placed in a dish of culture medium in the laboratory.AQA
gamete fertilisation: Statistical chance in fertilisation means empirical counts from small breeding trials may not match theoretical ratios exactly.OCR
gamete formation: A diploid precursor cell duplicates its chromosomes once and undergoes two successive nuclear divisions, yielding four genetically non-identical haploid…AQA, OCR
gametes: Sperm and ova, which are haploid, possessing exactly 23 chromosomes produced through meiotic reduction division.OCR
Gametes and fertilisation: Gametes are haploid: all egg cells carry an X chromosome, while sperm cells carry either an X or a Y chromosome, and at fertilisation these combine.AQA
gas collection apparatus: Equipment such as a gas syringe or an inverted measuring cylinder over water, used to collect oxygen released at timed intervals so that rate equals volume of…OCR
Gas exchange: The process in the lungs where oxygen diffuses from the alveoli into the blood and carbon dioxide diffuses from the blood into the alveoli to be exhaled.AQA
gas syringe: A 100 cm³ syringe readable to 1 cm³ in which gas volumes are collected, rather than counting irregularly sized bubbles.OCR
Gene: A short section of a DNA molecule that codes for a particular characteristic or for the sequence of amino acids in a protein.AQA, OCR
Gene expression: The process that non-coding DNA can help regulate, for example by controlling whether a gene is switched on or off.AQA
Gene insertion: The desired gene is inserted into plant cells and the modified cells are grown into plants.AQA
gene pool reduction: A severe reduction in the genetic diversity of the gene pool caused by selective breeding.OCR
Gene switching: Switching on specific genes so that particular proteins are made, giving the cell its specialised features.AQA
Gene therapy: An approach in which a normal allele is inserted into a patient's cells so that the correct protein is made.AQA
gene therapy risks and vectors: Gene therapy introduces functional alleles into target cells using viral vectors, but these can trigger severe immune reactions and off-target insertions can…OCR
Gene-environment interaction: The combined effect of genetic instructions and environmental conditions during development, so the phenotype is not fixed by genes alone.AQA
generation of genetic variation: Meiosis introduces genetic variation via crossing over and independent assortment.OCR
Generation time and rate of evolution: The change in the species can be relatively rapid because selection acts each generation, and the rate of change is faster in organisms with short generation…AQA
Genes: Parts of the genome that code for proteins that help build and control the organism and influence the development of characteristics.AQA, OCR
Genes and disease susceptibility: Comparing genomes of affected and unaffected people can reveal gene variants associated with conditions such as cancer or heart disease, aiding diagnosis and…AQA
Genes and genetic information: Each chromosome carries many genes, and the sequence of bases along the DNA determines the proteins that the cell can make.AQA
Genetic and fossil evidence: Later evidence from genetics, DNA sequencing, fossils and biogeography has refined and strengthened the theory of speciation.AQA
Genetic causes: Differences due to the genes individuals have inherited, coming from the alleles inherited from parents.AQA
Genetic continuity: Both cells have the same chromosome number and the same alleles as the parent cell, which matters for growth, repair and asexual reproduction.AQA
Genetic engineering: A process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.AQA, OCR
Genetic identity: Replication ensures that when the nucleus divides, each daughter cell receives a complete and identical set of genetic information.AQA
Genetic identity and variation: Cloned populations have little genetic variation, so they may all be vulnerable to the same disease or environmental change.AQA
Genetic information and inheritance: DNA is the molecule that stores genetic information.AQA
Genetic material: Material found in the nucleus of a cell that is composed of a chemical called DNA.AQA
genetic modification: Engineering staple crops with enhanced photosynthetic rates, drought resistance, and enriched nutritional content.AQA, OCR
genetic mutations: Spontaneous changes in the DNA base sequence that arise during replication and are the source of all genetic variants.OCR
genetic probability: Can be expressed as a fraction such as one quarter, a decimal such as 0.25, or a percentage such as 25%.OCR
Genetic variation: Produced through meiosis and random fertilisation in sexual reproduction, allowing populations to survive shifting environmental pressures.AQA, OCR
Genetic variation and comparison between organisms: Comparing genomes between species or individuals reveals evolutionary relationships and variation.AQA
Genetic variation in offspring: Sexual reproduction produces offspring that are genetically different from each other and from their parents.AQA
Genetic variation within populations: There is usually extensive genetic variation within a population of a species, meaning individuals differ in many alleles and so differ in many characteristics.AQA
Genetic variation within species: The range of genetic variation within a species is part of biodiversity, because populations with greater genetic variation are more likely to survive…AQA
Genetically modified (GM) crops: Crops that have had their genes modified in this way, with DNA altered by genetic engineering rather than by selective breeding.AQA
Genome: The entire genetic material of an organism, which is the complete set of instructions for building and maintaining that organism.AQA, OCR
Genome sequencing as a way to read genetic information: Studying a genome means reading the full base sequence of the DNA.AQA
Genotype: The alleles present for a gene, which operate at a molecular level to develop characteristics.AQA
Genotype and phenotype: The Y chromosome carries the gene that triggers testes development, so XY normally produces a male phenotype.AQA
genotypic and phenotypic ratios: Crossing two heterozygotes produces a 1:2:1 genotypic ratio and a 3:1 phenotypic ratio.OCR
Genus: The first part of a binomial name, written with a capital letter, which groups closely related species.AQA
Geographic change: A shift in the distribution of suitable conditions, for example a species' range moving towards the poles or to higher altitude as the climate warms.AQA
Geographical and reproductive isolation: Part of a population becomes separated, for example by a river, mountain range or island colonisation, so the two groups can no longer interbreed freely.AQA
Geographical distribution of species: The pattern that species vary geographically and that similar species often live in neighbouring regions.AQA
Geological processes: Processes such as plate movement, mountain building, volcanic eruptions, erosion and metamorphism that can crush, melt, heat or wear away fossil-bearing rock.AQA
geometric calculations: For model cuboidal organisms of side length s, surface area is calculated as 6s² while volume is calculated as s³.OCR
gibberellins: Play key roles in breaking seed dormancy, promoting the synthesis of amylase enzymes during germination, stimulating stem elongation, and promoting flower…OCR
Glands: Effectors that respond by secreting a chemical, such as a hormone, into the blood.AQA
Glands as endocrine organs: The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream.AQA
Global and local scales: Biodiversity can be considered on a global scale, covering all species on Earth, or on a local scale within one ecosystem such as a pond or woodland.AQA
Global food trade: Foods are transported around the world by ship, air and road from where they are produced to where they are eaten.AQA
global health transitions: As developing countries industrialise and adopt Western diets alongside rising tobacco and alcohol consumption, non-communicable disease incidence now…OCR
Global warming: The rise in average global temperature resulting from a strengthened greenhouse effect.AQA
Glucagon: A hormone secreted by the pancreas when blood glucose concentration becomes too low, stimulating the breakdown of glycogen to glucose to raise blood glucose…AQA, OCR
Glucose: What lactic acid is converted back into in the liver, which requires oxygen.AQA
glucose and starch: Glucose monomers polymerise into starch for energy storage in plants, and are released by breakdown for respiration.OCR
Glucose as respiratory substrate: Glucose is the main respiratory substrate, and a large proportion of the glucose produced by photosynthesis or absorbed from food is used in respiration…AQA
Glucose production: A process that falls when the rate of photosynthesis falls, leaving the plant with less glucose for growth.AQA
Glucose syrup: Supplied to the fungus as a nutrient and energy source.AQA
glycerol and fatty acids: Lipids are formed from the combination of glycerol and fatty acids, and lipase enzymes break lipids down into these for cellular respiration.OCR
glycogen: The insoluble storage polysaccharide into which soluble glucose is converted inside liver and muscle cells by enzymes stimulated by insulin.AQA, OCR
GM crop benefits and risks: Agronomic benefits include increased crop yields, reduced reliance on chemical pesticide sprays, enhanced drought and flood tolerance, and improved…OCR
Golden rice: A GM rice containing added genes that let it make beta-carotene, which the human body converts into vitamin A.AQA
Gradient: On a mass-loss or gas-volume graph, a steeper one indicates a faster rate of decay, while a flatter one indicates a slower rate.AQA
gradient calculations: On continuous product-time graphs, the initial rate of reaction is found by calculating gradient as change in y divided by change in x.OCR
Gradient of a tangent: A way to find rate from a curve of amount against time, using the initial, steepest part of the curve for the initial rate.AQA
gradients: Features of a graph that show how environmental stressors alter physiological rates until internal limits or plateaus are reached.OCR
graduated cylinder: Apparatus used to dispense volumes of sucrose solutions accurately.OCR
graduated measuring syringes: Apparatus marked in divisions, such as 1 cm³ or 5 cm³ syringes marked in 0.1 cm³ divisions, used to dispense liquid volumes of enzymes, substrates and buffers.OCR
Graph and table interpretation: Explaining what the pattern shows about risk, for example that as the number of cigarettes smoked per day increases, the risk of lung cancer increases.AQA
Graph construction: Choose a sensible scale, label both axes with quantity and unit, and plot points accurately.AQA
graph interpretation: Reading values at designated coordinates, identifying limiting factors, describing correlations and giving evidence-based biological explanations for…AQA, OCR
graph plotting: Plotting all data points accurately within half a small grid square using neat crosses.OCR
Graph skills: Reading values accurately from the axes, including the day and concentration of each peak, and comparing curves or describing trends.AQA
graphical interpretation: Reading corresponding values from curves, including determining the light intensity at which the photosynthetic rate reaches its plateau by reading the…OCR
graphical skills: Extracting and interpreting data from graphs, charts and tables, including checking the units and increments on both axes before reading values.OCR
Gravitropism: A directional growth response to gravity, in which auxin accumulates on the lower side, promoting upward growth in shoots and downward growth in roots.AQA, OCR
Greenhouse effect: Greenhouse gases absorb infrared radiation emitted by the Earth and re-radiate some of it back, so less heat escapes to space.AQA
Greenhouse gases and global warming: Carbon dioxide is a greenhouse gas, so its release contributes to the greenhouse effect and global warming.AQA
Growth: An increase in cell number by mitosis in multicellular organisms.AQA
Growth and biomass: Amino acids are used to build new cells and tissues for growth and repair, and growth involves building biomass.AQA
growth and repair: Biological purposes of mitosis, together with asexual reproduction, producing new cells for growth and repair of damaged tissues.AQA, OCR
Growth, repair and energy storage: Understanding synthesis and breakdown helps explain digestion, growth, repair, energy storage and the movement of substances in living organisms.AQA
Growth, repair and reproduction: Materials taken in are used for growth, repair, movement and reproduction.AQA
Guard cells: Two cells bordering each stomatal pore, which open and close the pore by changing shape as they gain or lose water.AQA

H

habitat destruction: Intensive land use such as deforestation, urban expansion, draining peat bogs and quarrying destroys natural habitats, fragmenting populations and triggering…OCR
Hairs: Structures that create a rough or irritating surface which is difficult to bite or walk on.AQA
haploid: Having a single set of unpaired chromosomes, such as 23 chromosomes in human gametes.OCR
Haploid and diploid: Gametes are haploid, meaning they contain half the normal number of chromosomes, so that the offspring has the correct diploid number after fertilisation.AQA
Haploid gamete formation: One starting cell yields four gametes, each with a single set of chromosomes.AQA
Haploid gametes and fertilisation: Gametes are haploid, so every egg carries one X while sperm carry either X or Y, and sex is determined at fertilisation by which sperm fuses with the egg.AQA
Harmful recessive alleles: Alleles that, when inherited from both parents, mean offspring may show inherited defects.AQA
Health: A state of complete physical, mental, and social well-being, rather than merely the absence of disease or infirmity.AQA, OCR
health and disease: A dynamic continuum in which diseases degrade overall health directly through organ dysfunction, while poor physical or social environments increase…OCR
Health and susceptibility to infection: Defects in the immune system mean an individual is more likely to suffer from infectious diseases, with increased frequency and often increased severity of…AQA
Health as physical and mental well-being: A state of physical and mental well-being, not just the absence of disease.AQA
health data translation: Translating complex information between graphical plots and numerical values, such as extracting mortality or infection statistics from epidemiological graphs.OCR
Healthy volunteers: People with no illness that could confuse results, used first to check safety and how the body handles the drug.AQA
Heart: An organ made mainly of cardiac muscle, which contracts rhythmically to pump blood.AQA
Heart attack: What a complete blockage of a coronary artery can cause when part of the heart muscle is starved of oxygen and dies.AQA
Heart failure: Occurs when the heart cannot pump blood effectively enough to meet the body's needs.AQA
Heart rate: The number of beats per minute, which increases during exercise to pump more oxygenated blood to the respiring muscles.AQA
heart rate and blood flow: Biological rates calculated as compound measures, with heart rate in beats min⁻¹ and blood flow through circulatory vessels in cm³ s⁻¹.OCR
Heart transplant: Replaces a damaged heart, offering the chance of a full recovery, but donor hearts are scarce, the operation is major and immunosuppressant drugs must be…AQA
heart transplants: Surgical option that carries a risk of donor organ rejection, requiring lifelong immunosuppressants.OCR
heart valves: Atrioventricular and semilunar valves that prevent backflow.OCR
heat shield: A transparent barrier, such as a flat-sided beaker of water, placed between the lamp and boiling tube to prevent heat from affecting the rate.OCR
Heat transfer by radiation and evaporation: Vasodilation widens skin arterioles so more blood flows near the surface and radiates heat, while evaporation of sweat removes latent heat from the skin.AQA
Helper T cells: Immune cells that coordinate the immune response and are especially attacked by HIV when the infection is not controlled.AQA
hemoglobin: Molecules packed inside erythrocytes that bind reversibly to oxygen.OCR
herbicide tolerance: A beneficial trait conferred by genetic modification, shown in crops engineered to resist broad-spectrum herbicides.OCR
Herbicide-resistant GM crops: Crops that contain a gene that allows them to survive a particular weedkiller, so a farmer can spray the field to kill weeds without harming the crop.AQA
Herbivores: Animals that eat plants or algae, and in a food chain they occupy level 2 and are named primary consumers.AQA
Herd immunity: When a large proportion of a population is immunised, the pathogen cannot easily pass from person to person, so the spread of disease is reduced and…AQA
Heritability of desired characteristics: The chosen parents must be able to pass the characteristic to their offspring.AQA
Heterozygous: Describes an organism with one dominant allele and one recessive allele present, where the dominant allele determines the characteristic.AQA
Hierarchical classification: Working logically down the hierarchy from kingdom to species, narrowing the group step by step.AQA
high-power microscopic resolution: Examining specimens under high magnification, such as 400x or oil immersion, using fine focus adjustment to resolve cellular detail.OCR
Histogram: A graph that shows frequencies for continuous data, with bars touching.AQA
histograms: Represent continuous variables such as patient age distributions, resting heart rates or blood cholesterol levels, where bars touch and the area under the bar…OCR
Historical development of agriculture: Humans have been breeding food crops from wild plants and domesticating animals for thousands of years.AQA
history of genetics: The foundation of modern genetics was established in the 1860s by Gregor Mendel through quantitative breeding experiments on pea plants.OCR
HIV: A sexually transmitted retrovirus that destroys helper T cells, reducing immune function.OCR
HIV and tuberculosis: A major clinical interaction in which HIV destroys helper T lymphocytes, and this immunodeficiency allows opportunistic bacteria like Mycobacterium…OCR
Holistic care: Treatment that addresses both physical and mental health together, such as treating pain, offering psychological support and encouraging social contact.AQA
homeostasis: The regulation of internal cellular and tissue fluid conditions to maintain a stable, optimal environment despite fluctuating external conditions.AQA, OCR
Homeostasis and control: Because the lungs and skin cannot regulate these losses, the kidneys must actively adjust the volume and concentration of urine to maintain the body's water,…AQA
Homeostasis and kidney function: The kidneys help maintain the water balance of body fluids by adjusting water loss in urine.AQA
Homeostasis and movement: The use of respiratory energy for muscle contraction enabling movement, and in mammals and birds to maintain a steady body temperature in colder surroundings.AQA
Homeostasis and negative feedback: Responses such as sweating, vasodilation, shivering and vasoconstriction are coordinated by the nervous system as negative feedback, restoring core…AQA
Homeostasis as protection for cell processes: Homeostasis maintains optimum temperature and pH so enzyme-controlled reactions continue at a suitable rate, and because enzymes control cell processes this…AQA
Homeostasis of water balance: The maintenance of a constant internal environment, shown by the control of the water level in the body.AQA
Homeostasis within the digestive system: Bile is alkaline, so when it enters the small intestine it neutralises the acidic chyme arriving from the stomach.AQA
homeostatic data: Data from graphs, charts and tables showing physiological variables, from which baseline set points and the magnitude of deviations following challenges can…OCR
Homologous chromosomes: 22 pairs are homologous autosomes, but in males the X and Y sex chromosomes are not fully homologous.AQA
Homozygous: Describes an organism when the two alleles present for a gene are the same, such as TT or tt.AQA
Homozygous dominant and homozygous recessive: A homozygous organism has two identical alleles, which can be two dominant alleles, such as TT, or two recessive alleles, such as tt.AQA
Homozygous recessive genotype: A genotype in which two copies of the recessive allele are present, so the recessive characteristic appears with no dominant allele present.AQA
Horizontal gene transfer: The way resistance can spread between bacteria, passing resistance genes to other strains or species.AQA
hormonal control: Delivery of synthetic oestrogen and progesterone to inhibit pituitary secretion of follicle-stimulating hormone and luteinising hormone, preventing egg…AQA, OCR
Hormonal control by ADH: ADH is the hormone produced by the pituitary gland that controls the water level in the body.AQA
Hormonal control of the menstrual cycle: Hormonal methods such as the combined pill alter the natural cycle so no egg matures, and the pill inhibits FSH so eggs do not mature.AQA
Hormonal coordination: The sequence runs from adrenaline release to increased heart rate, then to faster delivery of oxygen and glucose, and finally to more energy available in the…AQA
hormonal feedback: Rising oestrogen inhibits follicle-stimulating hormone release, while high oestrogen triggers a luteinising hormone surge, and progesterone inhibits both…OCR
Hormonal interactions: The sequence of hormonal interactions in which each hormone is linked to the next in a cause-and-effect chain.AQA
Hormonal regulation of fertility: Methods deliver oestrogen, progesterone or both to disrupt the normal cycle, usually by inhibiting FSH so eggs do not mature or by thickening cervical mucus.AQA
Hormonal responses: Usually slower and longer lasting than nervous responses, acting throughout the body.AQA
Hormone concentration changes: The order of the peaks, with FSH early, then oestrogen, then LH, then progesterone, and a fall in progesterone and oestrogen near the end corresponding to…AQA
hormones: Chemical messengers synthesised and secreted by ductless endocrine glands directly into the blood.OCR
Hormones as chemical messengers: Hormones are chemical messengers carried by the blood.AQA
Horticulture: Involves garden and ornamental plant production, and plant growth hormones are used in it to control plant growth.AQA
Host: The human, in whom the protist multiplies in red blood cells and causes symptoms.AQA
Host-pathogen interaction: Viruses enter host cells and use the host's machinery to make many copies of themselves, then burst out and infect more cells.AQA
HPV and cervical cancer: An interaction in which high-risk strains of sexually transmitted HPV integrate viral DNA into cervical epithelial cells, disrupting normal cell cycle…OCR
human ecosystem impact: Anthropogenic activities exert powerful positive and negative influences on ecosystems and global biodiversity, from land use and hunting to conservation…OCR
Human impact on ecosystems: The indirect effect of changed farming practice, such as spraying weedkillers that remove wild plants growing among the crop.AQA
Human impact on the environment: Activities such as deforestation, pollution, overfishing, hunting and building that reduce biodiversity by destroying or fragmenting habitats.AQA
Human interaction: Direct effects such as deforestation, drainage, pollution and building, and indirect effects such as introducing species or changing land use.AQA
Human population growth: The human population is rising, which raises demand for food.AQA
Human reaction time: How quickly a person responds, measured in the ruler drop test by the distance the ruler falls before it is caught, where a shorter distance indicates a…AQA
Human selection over many generations: Humans choose which individuals reproduce, so desired inherited characteristics become more common in later generations.AQA
Human versus financial cost: Human costs include pain, disability, reduced quality of life, premature death and emotional strain on families and carers, while financial costs include…AQA
Human-directed selection: Humans choose which characteristic to select for, based on usefulness, appearance, or behaviour, rather than natural selection.AQA
Hybridoma: A single cell created by fusing a B lymphocyte with a tumour cell, which can both divide and make the antibody.AQA
hybridoma technology: A mouse is injected with a specific antigen, then antibody-producing lymphocytes from its spleen are fused with myeloma cells to form hybridoma cells.OCR
hydrogen bonding: Bases pair via hydrogen bonds, with adenine pairing with thymine and guanine pairing with cytosine.OCR
Hydrogen bonding between bases: The two complementary strands are held together by hydrogen bonds between bases on opposite strands.AQA
hydrogencarbonate indicator colorimetry: Using hydrogencarbonate indicator enclosing pondweed or immobilised algae balls, which changes from red to purple as carbon dioxide is absorbed, providing a…OCR
Hydrolysis: Digestion in which water is used to break peptide bonds, releasing smaller peptides and eventually individual amino acids.AQA
Hydrolysis of biological polymers: Water is used to split the ester bonds joining glycerol to fatty acids, producing glycerol and fatty acids.AQA
hydroponics: Growing plants in aerated, mineral-rich nutrient solutions without soil, allowing year-round indoor vertical farming.OCR
Hygiene and sanitation: Measures such as hand washing, disinfecting surfaces and safe food preparation that remove pathogens and prevent contamination.AQA
Hyperopia: Long sightedness, where the eyeball is too short or the lens is too weak, so rays from a near object would focus behind the retina.AQA
hypothalamus: Monitors blood temperature, osmolarity, and blood glucose, directing homeostatic responses.OCR

I

Ideal growth conditions: Conditions with unlimited nutrients and no deaths, which the calculation assumes and which give a theoretical maximum.AQA
Identical daughter cells: The two cells formed are genetically identical to each other and to the parent cell because each receives one full set of chromosomes.AQA
Immune defence against pathogens: The immune system defends the body against pathogens such as bacteria, viruses, fungi and protists, using white blood cells to engulf pathogens and produce…AQA
Immune reactions and allergy: An immune reaction initially caused by a pathogen can trigger allergies such as skin rashes and asthma, with symptoms arising from immune chemicals such as…AQA
Immune rejection and immunosuppression: Immunosuppressant medicine is needed to reduce the chance of the immune system rejecting the transplanted organ.AQA
Immune response: The body's defence that is weakened when immune cells are destroyed, reducing the ability to fight other pathogens.AQA
Immune system: When a pathogen gets past the non-specific defences, this responds specifically to that pathogen and destroys it.AQA
Immune system function and failure: Infection with HIV destroys lymphocytes, so the immune system cannot control other pathogens and the person may develop AIDS-related infections.AQA
Immunity: The pathogen is destroyed before it can cause illness, so the person is immune to that pathogen without having suffered the disease.AQA
Immunity and vaccination: Memory cells remaining after infection give a faster, larger antibody response on re-infection, often preventing illness, and vaccination works in the same way.AQA
immunological memory: Some white blood cells remain in the blood as memory cells after a first exposure, whether through infection or vaccination.AQA, OCR
Impact of On the Origin of Species: The book set out the evidence and the mechanism in detail, reaching a wide audience and changing biology.AQA
Impact of technology on biological knowledge: Improved microscopy has driven advances in cell biology, medicine and biotechnology.AQA
Impact on biological thought: The ideas gave biology a unifying explanation for adaptation, biodiversity and the fossil record, and prompted questions about the age of the Earth and the…AQA
in vitro fertilisation: Ova are harvested surgically, fertilised with sperm in laboratory culture dishes, and grown into early embryos before transfer into the prepared uterus.OCR
In Vitro Fertilisation (IVF): A treatment in which a woman is given FSH and LH to stimulate the maturation of several eggs, which are collected and fertilised by sperm in a laboratory.AQA
Inbreeding: Breeding together closely related individuals, which increases the chance that harmful recessive alleles are inherited from both parents.AQA
inbreeding depression: Increased prevalence of inherited genetic defects and harmful recessive genetic disorders resulting from inbreeding.OCR
Incidence at different scales: Incidence means the number of new cases in a population over a period, and lifestyle factors can change incidence at local, national and global levels.AQA
Incident light: Light falling on a producer; only about 1 % of its energy is transferred into biomass.AQA
Incomplete fossil record: The gaps in the record of past life that result from geological activity destroying many traces, especially of the earliest and most fragile organisms.AQA
Incomplete oxidation of glucose: When oxygen is insufficient, glucose is not completely oxidised to carbon dioxide and water, and partial breakdown produces lactic acid.AQA
Incubation at 25°C: In school laboratories this reduces the likelihood of growing microorganisms harmful to humans, while still permitting growth for study.AQA
Incubation conditions: Plates are incubated upside down at a suitable temperature, typically around 25 °C in school laboratories, to reduce condensation and limit the growth of…AQA
independent and dependent variables: The independent variable is plotted on the horizontal x-axis, while the dependent variable is placed on the vertical y-axis.OCR
Independent discovery: Reaching the same conclusion as another person without seeing their unpublished work, as when Wallace reached the same conclusion as Darwin.AQA
Independent discovery and collaboration: Wallace independently reached the same mechanism as Darwin, and the work was published jointly in 1858.AQA
independent events: Each fertilisation is completely independent of previous events, so previous offspring do not influence future births.OCR
independent variable: The variable that is changed, such as direction of light or orientation relative to gravity.AQA, OCR
Index: The integer n in standard form; it is positive for numbers greater than or equal to 10 and negative for numbers less than 1.AQA
Industrial fermentation: Growing microorganisms in large quantities in fermenters under controlled conditions to make useful products.AQA
Infectious disease: A disease that can be transmitted between organisms, since infectious means the disease can spread between hosts.AQA
Informed judgement: Weighing benefits against drawbacks and stating a clear, justified conclusion, using the information provided rather than relying only on general opinion.AQA
Inheritance: The process by which offspring inherit features from each parent because the zygote contains genetic information from both.AQA
Inheritance from both parents: One chromosome of each pair is inherited from each parent, and this pairing is the basis of inheritance.AQA
Inheritance of acquired characteristics: The idea that changes that occur in an organism during its lifetime can be inherited.AQA
Inheritance of alleles: The alleles for useful characteristics are present in the gametes and are therefore inherited by offspring.AQA
Inheritance of sex: Females have two X chromosomes and males have one X and one Y chromosome, and the Y chromosome carries the gene that triggers male development.AQA
Inheritance of the introduced gene: The introduced gene becomes part of the plant genome and can be inherited.AQA
inheritance risks: If a heterozygous carrier couple has an affected child, the probability of their next child inheriting the condition remains strictly 25%.OCR
Inherited characteristics: Features already present in some individuals that are passed on and are not changes made during an organism's lifetime.AQA
Inherited defects: Defects that offspring may show when harmful recessive alleles are inherited from both parents.AQA
Inherited disorder: A condition caused by the inheritance of certain alleles passed from parents to offspring in gametes.AQA
Inherited disorders: Conditions caused by faulty alleles that are passed from parents to offspring.AQA
Inherited disorders and their treatment: Identifying the faulty allele behind a disorder such as cystic fibrosis helps explain how it is inherited and supports treatments such as gene therapy.AQA
Inherited variation: Variation that is the raw material on which natural selection acts, because some alleles give a survival advantage.AQA
initial rate and tangent calculations: The initial rate is found from the tangent to the steepest part of a product-time curve, giving the most valid measure of enzyme activity before substrate…OCR
Injection rather than swallowing: Used because insulin is a protein and would be digested in the stomach, so it cannot be taken as a tablet.AQA
Insect-resistant GM crops: Crops that contain a gene that makes a protein harmful to specific insect pests, so the insect dies after eating the plant and the crop suffers less damage.AQA
Insufficient oxygen supply: The condition during vigorous exercise when muscles use oxygen faster than the blood can deliver it, so anaerobic respiration takes place.AQA
Insulin: A hormone secreted by the pancreas into the blood when blood glucose concentration rises, increasing the permeability of liver and muscle cell membranes to…AQA, OCR
Insulin action: Lowering blood glucose by promoting glucose uptake and glycogen storage, so a slower fall in blood glucose links to reduced insulin action or reduced insulin…AQA
Insulin injection: A treatment for Type 1 diabetes, usually given several times a day, alongside monitoring blood glucose and diet.AQA
Insulin injections: The normal treatment, replacing the missing hormone so that glucose can be taken up by liver and muscle cells and stored as glycogen.AQA
insulin resistance: A condition in which the body's target cells become resistant to insulin, while the pancreas still produces it.AQA, OCR
Insulin sensitivity: The responsiveness of body cells to insulin; exercise can improve it so glucose is taken up more effectively.AQA
integrated homeostasis: The body maintains homeostatic equilibrium through integrated neural, behavioural, and endocrine responses to physiological stress.OCR
Integration of information: The centre combines both sets of information to decide whether to activate cooling or warming responses.AQA
Interaction of genetics, lifestyle and environment: Factors that can interact include genetics, lifestyle choices and environmental exposures, and together these can raise risk more than any one factor alone.AQA
Interactions between diseases: Different diseases often interact, and understanding these interactions helps explain why treating one disease can improve overall health and why prevention…AQA
Interactions in communities: Relationships between organisms within a community, such as predation, competition or interdependence, which patterns in data can be linked to.AQA
Interactions within ecosystems: The biotic and abiotic parts affect each other constantly, and a change in one part can affect other components of the ecosystem.AQA
Interdependence: Species in a community are linked by feeding and other dependencies, so a change in one population can change others.AQA, OCR
Interdependence and food supply: The link by which prey give predators more food, and a fall in prey reduces food for predators, so predator numbers fall.AQA
Interdependence between organisms: Organisms depend on each other, for example plants supply food and oxygen while animals pollinate flowers and disperse seeds.AQA
Internal and external stimuli: Changes that may come from inside the body, such as a rise in blood glucose after a meal, or from outside, such as cold air lowering body temperature.AQA
internal environment: The internal cellular and tissue fluid conditions that are regulated to remain constant and stable despite external fluctuations.OCR
international conservation agreements: Securing these requires complex political consensus between developing and developed nations, and they are difficult to gain and monitor.OCR
Interphase: The part of the cell cycle during which the cell grows, organelles increase and DNA is replicated so each chromosome becomes two identical copies.AQA
Interpret: Describe the trend, compare values between species or time periods, and link the pattern to a biotic factor such as predation, disease, food supply or…AQA
Interpret information: Describe the overall trend, quote figures with units, and explain the trend using biology.AQA
Interpret rate from a graph: Calculating the gradient of a straight-line section.AQA
Interpreting evolutionary trees: Reading a branching diagram to locate the common ancestor at a branching point and trace the branches to the species being compared.AQA
Interpreting given information: Reading the passage or diagram provided in the question and using it to explain the mechanism.AQA
Interpreting micrographs: When interpreting an electron micrograph, scale bars and known organelle shapes are used to identify structures rather than guessing from size alone.AQA
Intrauterine devices: Prevent the implantation of an embryo or release a hormone.AQA
Invasion of tissues: Malignant cells invade neighbouring tissues and can damage them.AQA
inverse proportion: Doubling distance does not halve intensity; intensity falls by the square of the distance factor, which is inverse proportion, not inverse linear.OCR
inverse square law: Light intensity is proportional to 1 / d², so doubling the distance gives one quarter and tripling gives one ninth.AQA, OCR
inverse square law calculations: Relative light intensity is proportional to 1 / d², where d is the distance from the light source to the plant.OCR
involuntary response: A rapid, automatic reaction that does not require conscious thought and shields organisms from physical trauma.OCR
Iodine solution: The reagent used to test for starch, turning blue-black when starch is present and remaining orange-brown when starch is absent.AQA
iodine test: A sample is transferred to a spotting tile well containing iodine solution, and the endpoint is reached when the iodine no longer turns blue-black and stays…OCR
Iodine test for starch: Iodine solution is yellow-brown and turns blue-black in the presence of starch.AQA
Iris: Controls pupil diameter, and in dim light its radial muscles contract and circular muscles relax, widening the pupil.AQA
isolation mechanisms: Geographical or reproductive isolation that prevents gene flow between separated populations, such as through geographic barriers like mountain ranges or…OCR
isotonic point: The point where the curve intersects the horizontal axis, where the external sucrose concentration equals the internal solute concentration of the plant cells.OCR
IVF: A treatment in which a mother is given FSH and LH to stimulate the maturation of several eggs.AQA
IVF treatment sequence: Laboratory fertilisation allows fertilisation to be observed and controlled before any embryo is transferred to the mother's uterus.AQA

J

Justification: Giving a reason for a rank by quoting the feature from the information that supports your answer.AQA

K

Keystone species: A species that has a disproportionately large effect on the community relative to its abundance.AQA
Kidney function: Filtering the blood and varying urine volume and concentration to maintain water balance, and excreting nitrogenous metabolic waste, specifically urea,…AQA, OCR
Kidney function and urine formation: The kidneys filter the blood, removing water, ions and urea from it, and these leave the body in urine.AQA
kidney gross anatomy: The kidney has three gross regions: the outer cortex, the medulla, and the central renal pelvis, which leads into the ureter.OCR
Kidney transplant: Replacement of the failed kidney with a donor organ, which can restore normal kidney function but carries risks of rejection.AQA

L

Labelled drawings: Accurate drawings of observed cell structures using straight uncrossed label lines and including a magnification or scale where required.AQA
Laboratory research: Monoclonal antibodies are used to locate specific molecules in cells or tissues.AQA
lactic acid: The product of anaerobic respiration in muscles, formed when glucose is broken down without oxygen during vigorous exercise.AQA, OCR
Lactic acid accumulation and removal: Lactic acid accumulates in muscle cells and diffuses into the blood, then is transported to the liver where it is converted back to glucose.AQA
Land pollution: Pollution that can occur on land, from landfill and from toxic chemicals.AQA
Large-scale production: The hybridoma clone is grown on a large scale so that antibody accumulates in the culture medium, giving a much greater volume than could be obtained from…AQA
Laser surgery: A procedure that permanently reshapes the cornea so its refractive power matches the eyeball's length, removing the need for glasses.AQA
Late stage HIV infection: Occurs when the body's immune system becomes so badly damaged it can no longer deal with other infections or cancers.AQA
lawn spreading technique: A sterile bacterial lawn is spread evenly across nutrient agar using a sterile spreader or inoculating loop.OCR
leaf starch test: Boiling a leaf in water, decolourising it in hot ethanol and staining with iodine solution on a white tile to observe starch distribution.OCR
Leak: When a valve develops a leak, it does not close completely, so blood flows backwards instead of moving on.AQA
LED lighting: A cool light source that emits minimal heat, used instead of incandescent bulbs so that light intensity is the only manipulated variable.OCR
Lens: This becomes thicker and more curved when the suspensory ligaments are loose, and a thicker lens refracts light rays more strongly.AQA
Level 4: The third consumer level in a food chain, containing carnivores that eat other carnivores.AQA
Levels of ecological organisation: Organisation in an ecosystem runs from a single individual organism to a population, a community and the whole ecosystem.AQA
Levels of organisation: A tissue is a group of similar cells working together, an organ is several tissues working together, an organ system is several organs working together, and…AQA
Life cycle: The stages in which the malarial protist develops and multiplies inside the mosquito before reaching its salivary glands and passing into a healthy person's…AQA
Life situations: These include housing, income, education, employment and social support, and poor ones can increase stress and limit access to healthy food and healthcare.AQA
Lifestyle aspects: The choices and behaviours a person controls, such as diet, exercise, smoking and alcohol intake.AQA
lifestyle changes: Non-invasive measures such as a diet low in saturated fat, stopping smoking and regular exercise, which lower blood pressure but depend on long-term patient…OCR
Lifestyle factors: Risk factors that are lifestyle choices, such as smoking, poor diet, alcohol use and lack of exercise.AQA
Lifestyle management of disease: Diet and exercise together can lower blood glucose and may reduce the need for medication in Type 2 diabetes.AQA
lifestyle risk factors: Diet, alcohol and smoking affect the incidence of non-communicable diseases, with a diet high in saturated fat, salt and sugar, alcohol misuse and smoking…AQA, OCR
ligase: Enzyme that joins the gene and plasmid together by forming covalent phosphodiester bonds, producing recombinant DNA.AQA, OCR
light intensity: Increasing this supplies more radiant energy to excite electrons in chlorophyll, raising the rate proportionally until another factor limits.AQA, OCR
Light microscope: Apparatus selected and safely used to observe, draw and label cells, starting on the lowest power objective to locate the specimen.AQA
light microscopy: A lamp shines light through a thin specimen on a glass slide held on the stage by clips, and the objective lens and eyepiece lens both magnify the image.OCR
lignification: Thickening and reinforcement of xylem vessel walls with waterproof lignin spirals, which resist collapse under negative hydrostatic tension.OCR
Limitations of specimen preparation: Specimens for electron microscopy are usually dead and dehydrated, which is a limitation when studying living cells.AQA
limiting factor: The factor in shortest supply that holds the rate below its potential maximum.AQA, OCR
limiting factors: The principle that the rate of a process is determined by the factor in shortest supply, such as light intensity, CO₂ concentration and temperature for…AQA, OCR
Limiting factors and competition: If any required material is in short supply, growth and reproduction are limited, which is why competition matters.AQA
Limiting factors on growth: Growth eventually slows as nutrients are used up and toxic waste products build up, so the rate is not maintained indefinitely.AQA
Limiting movement: Reduces energy transferred by muscle contraction and movement, so more energy remains in biomass.AQA
Limiting resources: Light, space, water and mineral ions are finite, so plants that capture more of a resource leave more offspring.AQA
Limits of diffusion in multicellular organisms: A large multicellular organism has a smaller surface area to volume ratio and a longer diffusion distance, so diffusion alone cannot meet its needs and it…AQA
Limits of selective breeding: The process can take many generations and may be limited by remaining variation or inherited defects.AQA
Limits on food chain length: Too little biomass remains to support another level, which limits food chains to about four or five trophic levels.AQA
Limits on regeneration in animals: Limited division means mature animals cannot easily regenerate complex body parts, unlike many plants.AQA
line of best fit: A single, smooth, continuous line or curve reflecting the biological trend, without feathery lines or point-to-point joins.OCR
linear scales: Evenly spaced scales for both axes, using sensible intervals, chosen so that plotted points occupy at least half the grid area.OCR
Linking evidence to theory: Stating what a change in hormone level causes, rather than describing the shape of a curve without linking it to a biological event.AQA
Links between practical work and medical application: The zones of inhibition measured show how well an antibiotic stops bacterial growth, linking the practical to antibiotics and painkillers.AQA
Linnaean system: A system developed by Carl Linnaeus that places organisms into a hierarchy of groups, from the broad kingdom down to the species, with each level becoming…AQA
Lipases: Produced in the pancreas and the small intestine, they act on lipids, breaking them down to fatty acids and glycerol.AQA
lipid digestion: Lipase enzymes hydrolyze lipids back into glycerol and fatty acids for respiration.OCR
Lipid emulsion test: Ethanol is added to an unfiltered sample, shaken, then poured into water, and a cloudy white emulsion indicates lipid.AQA
lipid synthesis: Synthesized lipids provide concentrated long-term energy storage, thermal insulation, protection of vital organs, and formation of phospholipid cell membranes.OCR
Liver: The organ to which blood transports lactic acid, where it is converted back into glucose.AQA
Liver and glycogen: The liver acts as the main store of glycogen, a storage polysaccharide, and the key target organ for glucagon.AQA
Liver and muscle function: Glycogen is stored in the liver and in muscle tissue, and when blood glucose concentration falls, glucagon stimulates its breakdown back into glucose.AQA
Liver function: Processing amino acids rather than excreting them unchanged, making the liver central to homeostasis.AQA
Liver function and glucose recycling: In the liver, hepatocytes use oxygen in reactions that convert lactic acid back into glucose, which can be released into the blood and used by muscles,…AQA
Liver function in metabolism: The liver converts lactic acid back to glucose, a process that requires oxygen.AQA
living plant welfare and preservation: Careful handling of living plants, keeping aquatic plants fully submerged in a suitable aquatic medium and returning them safely to aquaria.OCR
Living transport tissue: Phloem cells are living, which supports the energy-dependent processes of translocation.AQA
Local extinction: When a species disappears from a particular area, even if it survives elsewhere.AQA
lock and key hypothesis: Each enzyme possesses an active site with a rigid, complementary three-dimensional shape that binds only one specific substrate to form an enzyme-substrate…OCR
Long sight: A defect in which the image would form behind the retina, often because the eyeball is too short or the lens too weak.AQA
loop flaming: Metal inoculating loops are heated to red heat along their length and air-cooled before transferring bacteria.OCR
Luteinising hormone: A hormone whose surge, triggered by rising oestrogen from the follicle, causes the follicle to rupture and release the egg.AQA
Lymphocytes: White blood cells that produce a particular antibody complementary to the injected antigen.AQA
lysis: The bursting of an animal cell when water enters by osmosis and the increased internal hydrostatic volume stretches the cell membrane until it bursts.OCR
lysozyme: An antimicrobial enzyme produced in tears to wash and protect eye surfaces, breaking down bacterial cell walls.OCR

M

Magnesium deficiency: A shortage of magnesium ions, which are needed to make chlorophyll, so the plant cannot make enough chlorophyll and its leaves become pale or yellow.AQA
Magnesium ions: Needed to make chlorophyll, the pigment that absorbs light energy in photosynthesis, so a shortage causes chlorosis and less glucose is made.AQA
Magnification: Calculated from the objective lens and eyepiece lens values, with the total magnification shown in calculations of magnification and scale.AQA
Magnification and scale: A magnification scale included with a drawing, either as a scale bar or a statement such as 'magnification ×400'.AQA
magnification calculation: Total magnification is the eyepiece magnification multiplied by the objective magnification, and magnification equals image size divided by actual size, which…OCR
magnification formula calculations: Actual size is found from actual size = image size / magnification, with image size and actual size in the same unit.OCR
Maintenance of the physical environment: Processes such as nutrient cycling, soil formation and water retention carried out by living organisms, which several species can still provide if one declines.AQA
Malaria transmission: The malarial protist enters the human blood when an infected mosquito bites and feeds.AQA
Male secondary sexual characteristics: Features promoted by testosterone at puberty, such as deepening of the voice, growth of facial and body hair, and increased muscle development.AQA
Malignant tumour: A tumour that invades nearby tissues and spreads to other parts of the body.AQA
malignant tumours: Cancerous cells that invade surrounding tissues, break off, and travel via blood or lymph to form secondary tumours.OCR
Mapping regions to functions: This requires evidence from more than one method because each method has limitations.AQA
mass-flow transport: A transport system that multicellular organisms require alongside specialized exchange surfaces to meet metabolic demands.OCR
mass, gas volume and pH measurement: Mass is recorded with a balance, gas volumes may be collected in a gas syringe, and pH is measured with a pH meter or indicator paper.OCR
Maternal and fetal health: Chemicals in tobacco smoke, such as carbon monoxide, and alcohol can harm an unborn baby by crossing the placenta.AQA
mathematical conversions: Converting between fractional, decimal and percentage representations of ecological data, dividing the numerator by the denominator and multiplying by 100.OCR
Mathematical skills in biology: Covers calculations and graph work, including calculating means, rates and percentages, and interpreting graphs.AQA
Maturation of several eggs: The process stimulated by giving FSH and LH, ensuring multiple eggs mature simultaneously rather than only one per cycle.AQA
Mean: The arithmetic average: add all values and divide by the number of values.AQA
mean cell dimensions: Measuring several representative cells across the field of view and calculating a mean length reduces the effect of biological variation.OCR
Mean division time: The time taken for a bacterium to divide, used to find the number of divisions by dividing the total time by it.AQA
Measurement and units: Measure the diameter with a ruler, halve it to find the radius, and give the area in mm² or cm².AQA
Measurement, recording and reliability: Recording zone diameters in millimetres in a suitable table and repeating measurements to improve reliability.AQA
Measuring change over time: Measuring pH at regular intervals, for example every 24 hours, using a pH meter or universal indicator solution and recording readings at fixed times.AQA
Meat substitute: A food such as burgers, mince or nuggets in which mycoprotein is used in place of meat.AQA
Mechanical valves: Valves made from materials such as metal or polymer, which are very durable but increase the risk of blood clots, so patients usually need anticoagulant…AQA
Median: The middle value when data are ordered; for an even number of values, it is the mean of the two middle values.AQA
Medical applications: The purified antibody can then be used safely in medical diagnosis, research or treatment, because contaminants could affect results or cause unwanted effects…AQA
Medical applications of genetic engineering: Bacterial cells have been genetically engineered to produce useful substances such as human insulin, giving a reliable supply rather than relying only on…AQA
Medical applications of genomics: Predicting disease risk, selecting treatments, developing medicines and understanding inherited conditions, supported by understanding the human genome.AQA
Medical applications of stem cells: A bone marrow transplant can introduce healthy stem cells into a patient, for example to treat leukaemia, where donated stem cells divide and differentiate to…AQA
Medical diagnosis: Antibodies can detect specific molecules such as pathogens or markers of disease.AQA
Medical diagnosis and laboratory testing: Monoclonal antibodies are used in pregnancy tests and in laboratories to measure levels of hormones and other chemicals in blood, or to detect pathogens.AQA
medical gene technology: Gene technology in clinical medicine encompasses recombinant DNA technology and gene therapy, with practical and ethical considerations.OCR
Medicine specificity: Choosing a medicine depends on the cause of the disease and whether the aim is to kill the pathogen or relieve symptoms.AQA
Medicines: A treatment for Type 2 diabetes that may be used alongside diet and exercise to lower blood glucose.AQA
Medulla: The stalk-like region at the base of the brain leading into the spinal cord, controlling unconscious activities such as heart rate and breathing.AQA
medulla oblongata: Sits in the brainstem, controlling involuntary autonomic life-support functions including heart rate, breathing rate, and gut peristalsis.OCR
meiosis: A specialised reduction division occurring exclusively in reproductive organs to generate haploid gametes.AQA, OCR
Membrane containment: The growth is contained in one area and is usually enclosed within a membrane.AQA
Memory cells: Cells the person produces so that if the live pathogen later enters the body, they recognise the same antigens and trigger a faster, larger antibody response.AQA, OCR
Mendel's experiments: In the mid-19th century breeding experiments on plants showed that inheritance of each characteristic is determined by 'units' passed to descendants unchanged.AQA
mendelian inheritance: Characteristics are determined by inherited units that pass unchanged to offspring, rather than blending as previously believed.OCR
menstrual cycle: A graph of this may show hormone levels (FSH, LH, oestrogen, progesterone), and the day ovulation occurs can be found by identifying the LH peak.AQA, OCR
menstrual regulation: Falling progesterone and oestrogen levels at the end of the cycle cause menstruation and allow follicle-stimulating hormone release.OCR
Mental well-being: Feeling positive about oneself, being able to cope with normal stresses, and having good emotional and social functioning.AQA
Meristem tissue: Found at the growing tips of shoots and roots, where unspecialised cells divide to produce new growth.AQA
meristematic growth: Meristem cells divide throughout the plant lifetime to produce new tissues for continuous apical and lateral growth.OCR
meristems: Specialized growing regions in plants where stem cells reside, predominantly located at the tips of growing roots and apical shoot buds, as well as in the…AQA, OCR
Meristems and plant growth: Many plant cells remain unspecialised in meristems and can differentiate throughout life as the plant grows or repairs damage.AQA
Messenger RNA: A copy of the gene's base sequence that carries the genetic message from the DNA in the nucleus to the ribosome.AQA
Metabolic disease and obesity: Obesity increases the risk of Type 2 diabetes because body cells become less responsive to insulin.AQA
metabolic rate: The rate at which metabolic reactions proceed, which depends on enzymes maintaining optimal tertiary structure and reaction rates.AQA, OCR
metabolic requirements: Oxygen is imported to serve as the terminal electron acceptor in aerobic respiration to supply ATP, while dissolved food molecules are imported for energy and…OCR
Metabolism: Includes both building up and breaking down substances, with synthesis and breakdown controlled by enzymes.AQA
Metabolism and synthesis: The use of transferred energy to build larger molecules from smaller ones, such as synthesising proteins from amino acids.AQA
Metamorphosis: The change from tadpole to adult in amphibians such as frogs, which thyroxine triggers.AQA
Methane: A gas produced by anaerobic decay that is collected and burned as a fuel for heating, cooking or generating electricity.AQA
microbial smear preparation and heat-fixing: Mixing a loopful of culture in sterile water on a glass slide, air-drying, and heat-fixing gently over a Bunsen flame to adhere cells without distorting…OCR
microbiological assays: Tests of antiseptic or antibiotic efficacy in which filter paper discs soaked in antimicrobial agents are placed on inoculated agar lawns.OCR
microbiological scientific drawing: A drawing of observed microorganisms with clear continuous outlines, accurate proportions, labelled structures, and total magnification stated.OCR
Microorganisms and nutrient cycling: Bacteria and fungi act as decomposers, releasing carbon dioxide to the atmosphere and mineral ions to the soil so that materials continue to cycle through the…AQA
Microorganisms as useful organisms: Many microorganisms are useful and are cultured industrially for food and other products, rather than only causing disease.AQA
microscope operation and focus: The slide is viewed on a compound light microscope, starting on the lowest power objective, focusing with the coarse knob then the fine knob, before moving to…OCR
microscopy: Examination of tissue smears with portable light microscopes for fungal spores or bacterial exudates, used in field diagnosis.OCR
Mimicry: Making a plant resemble something else, such as another organism or an inedible object, so the herbivore avoids it.AQA
Mineral ion uptake by active transport: Ions are moved against their concentration gradient, from a lower concentration in the soil to a higher concentration inside the cell.AQA
Mineral ions and plant nutrition: Mineral ions such as nitrate, phosphate and potassium ions are released into the soil and taken up by plant roots to make proteins, DNA and other compounds.AQA
Mineral nutrition in plants: Plants absorb nitrate ions from the soil to synthesise amino acids and proteins, and fertilisers can be added to nutrient-poor soil to provide essential…AQA
Mineralisation: As soft tissue decays, dissolved minerals seep into the remaining hard parts and replace the original material, producing a mineral cast that keeps the shape…AQA
minimization of physiological stress: Avoiding lethal temperatures, bright heat lamps, dehydrating conditions and excessive confinement times when using living organisms to measure physiological…OCR
Mitochondria: Contain respiratory enzymes folded along inner cristae, functioning as the sites of aerobic respiration to generate ATP.AQA, OCR, Pearson Edexcel
mitochondria and ATP: Abundant mitochondria supply ATP through aerobic respiration for active transport.OCR
Mitosis: The stage in which replicated chromosomes condense and line up at the cell equator, and spindle fibres pull the sister chromatids to opposite poles.AQA, OCR
Mitosis and cloning: The hybridoma divides by mitosis to form a clone, and because cell division produces genetically identical cells, all the antibody produced is identical.AQA
Mitosis and differentiation: Mitosis produces more cells, whereas differentiation makes a cell specialised.AQA
Mitosis and embryo development: The egg is stimulated to divide by mitosis, and the resulting embryo must first divide to form a ball of cells before it is inserted into the womb.AQA
Mitosis and growth: The newly formed zygote divides by mitosis to produce genetically identical diploid cells, and repeated mitotic divisions cause the overall number of cells to…AQA
Mode: The most frequent value, useful for categorical data such as the most common species.AQA
moisture content: The mass of evaporated water expressed as a percentage of the original fresh mass, after heating samples until a constant dry mass is obtained.OCR
Molecular evidence: Evidence such as DNA base sequences and RNA, used by scientists such as Carl Woese to revise the classification system.AQA
Molecular evidence from RNA and DNA: Chemical analysis, particularly comparing RNA and DNA sequences, which showed that some organisms placed together in older systems are only distantly related.AQA
molecular phylogenetics: Precise phylogenetic mapping based on DNA base sequencing and protein analysis, used in modern classification developments.OCR
Molecules for growth and respiration: The bloodstream transports the absorbed products to cells for use in the body, for example amino acids are used to build new proteins in cells.AQA
Monoclonal: All the antibody molecules come from one clone of antibody-producing cells, so they are identical in shape.AQA
Monoclonal antibodies: Identical antibodies produced by a clone of hybridoma cells, which are then collected and purified from the culture medium where hybridomas are grown.AQA
Monoclonal antibodies and specificity: Antibodies produced from a single clone of cells, so they are identical and bind to one specific antigen.AQA
Monohybrid cross: A cross involving one gene with two alleles, in which each parent contributes one allele to each offspring.AQA
monohybrid crosses: Single gene crosses whose results are predicted using Punnett squares.OCR
monohybrid inheritance: Offspring genotypes and phenotypes emerge in predictable numerical proportions governed by the random fusion of gametes.OCR
monomer: A single sugar unit, such as glucose, that joins with others to synthesise carbohydrate polymers.OCR
monomers: Smaller repeating molecular units that link together in a long chain to form a polymer.OCR
MRI scanning techniques: These produce detailed images of brain structure and activity, allowing living brains to be mapped safely.AQA
mRNA: A complementary mRNA copy of the DNA base sequence is produced during transcription and carries the code to the ribosome.AQA
mRNA and tRNA: Messenger RNA leaves the nucleus through a nuclear pore to enter the cytoplasm, while transfer RNA molecules carry specific amino acids to the ribosome.OCR
MRSA: A resistant strain whose infections may not respond to commonly used antibiotics, increasing the risk of serious illness or death.AQA
mucus and ciliated cells: Goblet cells secrete sticky mucus to entrap pathogens and ciliated epithelial cells rhythmically beat to sweep mucus upward to the pharynx to be swallowed.OCR
Multicellular: Organisms, such as most plants and animals, that contain many cells which may be specialised for particular functions.AQA
Multifactorial disease causation: Many diseases are caused by the interaction of a number of factors rather than a single cause.AQA
multifactorial diseases: Non-communicable human diseases caused by the interaction of a number of factors, not a single cause.OCR
Multiple births: A risk that is raised by transferring more than one embryo, which also increases the chance of pregnancy.AQA
Multiple interacting risk factors: Many factors interacting can make it difficult to isolate one cause of a disease.AQA
multipotent: Describes adult stem cells, whose differentiation is restricted to a limited range of cell types related to their tissue of origin.OCR
Muscles: Effectors that respond by contracting, which shortens the muscle and moves a body part.AQA
Mutagens: Agents such as ultraviolet radiation or tar in cigarette smoke that increase the rate at which mutations occur.AQA
Mutation: A change in the base sequence that, in non-coding DNA, may have no effect on a protein or may affect how genes are expressed.AQA
Mutation and protein function: A changed shape can reduce a protein's strength or alter its function, and the effect depends on the function of the protein and the position of the changed…AQA
Mutation and protein shape: A few mutations code for an altered protein with a different shape, because a change in amino acid sequence can alter the way the polypeptide folds.AQA
Mutation as the source of new alleles: All new alleles arise by mutation, a random change in the base sequence of DNA, and mutation is the source of all new variation.AQA
mutations: Spontaneous mutations in DNA create new alleles that are continually shuffled through sexual reproduction during meiosis and random fertilisation.OCR
Mutations and reading frames: A substitution can change one amino acid, while insertion or deletion can shift the reading frame and change many amino acids.AQA
mutualism: A symbiotic relationship where both species derive reciprocal biological benefit, such as insect pollinators obtaining nectar while facilitating plant…AQA, OCR
mycoprotein: A high-protein meat substitute derived from the filamentous fungus Fusarium, cultured under continuous aerobic conditions with glucose syrup and mineral ions.AQA, OCR
myelin sheath: A fatty covering that insulates the axon and speeds up transmission of the nerve impulse.OCR
myeloma tumour cells: Cells that possess the capacity to divide indefinitely in laboratory cell culture and are fused with antibody-producing lymphocytes.OCR
Myopia: Short sightedness, where the eyeball is too long or the lens is too powerful, so rays from a distant object focus in front of the retina.AQA
myopia and hyperopia: Conditions where light fails to focus precisely on the retinal plane, with distant objects blurred in the first and close objects blurred in the second.OCR

N

Named examples of reproduction: The required examples are malarial parasites, fungi, and specific plants such as strawberries and daffodils.AQA
Natural fertilisation versus assisted reproduction: Fertilisation inside the body through intercourse in the normal way, rather than collecting eggs and fertilising them outside the body.AQA
Natural selection: The process by which individuals with characteristics better suited to their environment are more likely to survive and reproduce, so advantageous…AQA
Natural selection and survival advantage: When the environment changes, some individuals may have characteristics giving a survival advantage, and those surviving individuals reproduce and pass on the…AQA
Natural sources of drugs: Plants and microorganisms from which drugs were traditionally extracted.AQA
Natural sources of medicines: Many drugs were originally extracted from plants or microorganisms rather than being made synthetically from the start.AQA
negative control verification: A control disc soaked in sterile water is placed alongside the test discs to prove that the paper disc itself did not inhibit bacterial growth.OCR
Negative feedback: A mechanism in which the response counteracts the original change, reversing a change away from a normal level and returning the internal environment to its…AQA
Negative feedback control of water balance: After sweating heavily, blood becomes more concentrated, the pituitary gland releases more ADH, and water returns to the blood so urine volume falls.AQA
Negative feedback control systems: A loop in which the correction cancels the original change, restoring conditions towards the optimum by reversing the original change.AQA
negative feedback graphs: Graphs from which the time required for negative feedback mechanisms to restore normal physiological homeostatic equilibrium can be measured.OCR
nephron structure: A nephron starts at Bowman's capsule in the cortex and continues through the proximal convoluted tubule, the loop of Henlé and the collecting duct.OCR
Nervous impulse: What is generated when a temperature receptor is stimulated, travelling along a sensory neurone to the central nervous system.AQA
Nervous responses: Electrical impulses travel along neurones, and this is fast and short-lived, suiting rapid changes.AQA
Nervous system and reaction time: Linking practical evidence back to the biological function of the nervous system, including receptors, coordination centres and effectors.AQA
nervous tissue repair: Mature central neurones are specialised cells that do not readily undergo cell division, so damaged axons exhibit extremely limited regeneration.OCR
Net movement: The overall movement from an area of higher concentration to an area of lower concentration, even though individual particles move in all directions.AQA
Net size: Using a mesh large enough to let young, small fish escape while retaining larger adult fish, so juveniles can grow and breed before they are caught.AQA
neural pathways: Extensive branching networks that link all regions of the body to the Central Nervous System and distribute coordinated impulses to muscles and glands.OCR
Neurone adaptation: Neurones are long, have branched endings to connect with receptors and other neurones, and are insulated by a myelin sheath that speeds up transmission.AQA
neurone conduction: Conduction velocity graphs contrast myelinated neurones against unmyelinated fibres or explore physiological effects of stimulants and depressants.OCR
Neurone regeneration: The limited ability of mature neurones to divide, meaning damage to neurones is often permanent.AQA
New pathogen: A new pathogen can spread rapidly if the population has little immunity, reducing numbers before resistance builds.AQA
New phenotype: A changed characteristic of the organism that appears very rarely, only when a mutation alters the protein in a way that affects the organism.AQA
New predator: A new predator can reduce prey numbers directly, and may also alter prey behaviour, such as feeding less or hiding more.AQA
Niche and survival: These bacteria are adapted to that specific niche, where their cell membranes resist heat and pressure.AQA
Nitrate deficiency: A shortage of nitrate ions, which are needed to make amino acids and proteins, so the plant cannot build enough protein for new cells and shows stunted growth.AQA
Nitrate ions: Absorbed from the soil, their nitrogen is used to make amino acids, which are assembled into proteins, so a shortage reduces protein synthesis and restricts…AQA
Nitrogen balance: Maintained by removing surplus nitrogen from the body through deamination.AQA
nitrogen cycle: Nitrogen gas in the atmosphere is converted into mineral nitrates absorbed by plant roots to synthesise plant proteins, which are passed to consumers and…OCR
nitrogenous bases: The four different bases are adenine (A), thymine (T), guanine (G) and cytosine (C), attached to the sugar.OCR
non-coding DNA: Parts of DNA that do not directly determine the amino acid sequence of a protein, lying between genes and possibly within genes.AQA
Non-communicable disease: A disease that cannot be passed from one individual to another (e.g., heart disease, cancer).AQA
Non-communicable disease burden: Non-communicable diseases cannot be passed from person to person, and their burden includes human costs such as pain, disability, reduced quality of life,…AQA
Non-communicable disease risk factors: Coronary heart disease is non-communicable and is linked to risk factors such as a high saturated fat diet, smoking and high blood pressure.AQA
non-communicable diseases: Non-infectious conditions that cannot be transmitted from person to person and develop over time due to genetic predispositions, lifestyle habits, or…AQA, OCR
Non-lifestyle factors: Risk factors that are not directly chosen, such as age, genetics or exposure to radiation.AQA
Non-specific defences: Barriers including the skin, mucus, cilia, and stomach acid that try to stop pathogens entering.AQA
Nose: Traps pathogens using hairs and sticky mucus in inhaled air.AQA
Nuclear division: Mitosis is the stage where the nucleus divides and one copy of each chromosome moves to each end of the cell.AQA
Nucleotide: The repeating unit of DNA, containing a common sugar called deoxyribose, a phosphate group, and one of four different bases.AQA
Nucleotide components: Each nucleotide consists of a common sugar and phosphate group with one of four different bases attached to the sugar.AQA
nucleotide structure: Each nucleotide consists of a phosphate group, a common sugar and one of four different bases attached to the sugar.OCR
nucleotides: The individual monomers of nucleic acids, which link along their sugar and phosphate groups to build DNA.OCR
Nucleus: A structure bounded by its own membrane that holds the genetic material, DNA, separated from the cytoplasm.AQA, Pearson Edexcel
Nutrient broth: A liquid medium containing nutrients in which bacteria multiply throughout the solution, producing a cloudy suspension.AQA
nutrient cycling: Chemical elements essential for life continuously cycle between the biotic and abiotic components of ecosystems, ensuring that vital elements remain…OCR
nutrient recycling: The return of carbon dioxide to the atmosphere and mineral ions such as nitrates to the soil for plant root uptake.OCR
nutrient uptake: Dissolved food molecules and mineral ions such as nitrates and magnesium are imported for energy and biosynthesis.OCR

O

Obesity: Carrying excess body fat, often indicated by a high body mass index.AQA
Observable characteristics: Features such as the number of legs, the presence of a backbone, or the arrangement of leaves and flowers, on which the traditional system is based.AQA
Obtaining materials from other organisms: Animals cannot photosynthesise, so they obtain energy and building materials by eating other living organisms.AQA
Obtaining materials from the environment: Organisms take a supply of materials from their non-living surroundings, such as carbon dioxide from the air and water and mineral ions from the soil.AQA
Oestrogen: Secreted by the ovary as the follicle develops, it stimulates the uterus lining to thicken and repair after menstruation.AQA
Offspring: The young produced when selected parents are bred together, which inherit alleles from both parents.AQA
One-way flow through the heart: Flap-like structures called valves keep blood flowing one way through the heart by closing between contractions to prevent backflow.AQA
Opportunistic infections: Infections that would normally be harmless but can cause serious illness when immunity is lost.AQA
optic nerve: The nerve along which impulses travel from retinal receptors to the brain, which interprets them as vision.AQA
optical lenses: Concave diverging lenses correct short-sightedness and convex converging lenses correct long-sightedness by refracting light to focus on the retina.OCR
Optimum conditions for cell function: The conditions that must be maintained so that enzymes and cells can function effectively.AQA
Optimum dose: The dose that gives the best therapeutic effect with acceptable side effects, balancing benefit against harm rather than being simply the highest dose.AQA
Optimum pH: The pH at which an enzyme works best, differing between enzymes such as pepsin in acidic stomach conditions and intestinal enzymes in alkaline conditions.AQA
Oral contraceptives: Contain hormones to inhibit FSH production so that no eggs mature.AQA
Order of magnitude: A factor of ten, so a cell 100 µm across is two orders of magnitude wider than one 1 µm across.AQA
Organ: An aggregation of tissues performing specific functions, made from several different tissues that work together to carry out a particular function.AQA
Organ damage and cancer: Alcohol damages liver cells, causing cirrhosis, and impairs brain function, while smoking damages lung tissue, causing chronic obstructive pulmonary disease,…AQA
Organ system: A level of organisation formed when organs are built up together, contributing to the functioning of the whole organism.AQA
Organelle function: Ribosomes assemble proteins and mitochondria release energy by respiration for the processes of growth and division.AQA
Organism: The coordinated whole formed by organ systems interacting so that all the processes needed for life can be carried out.AQA
origin of variation: All variants arise from mutations, which are spontaneous changes in the DNA base sequence arising during replication.OCR
osmoregulation: The kidneys are the primary organs of this in humans, maintaining the water potential of blood plasma and tissue fluid within narrow limits.OCR
Osmoregulation by ADH: ADH controls the permeability of the kidney tubules to water, and its concentration in the blood changes how much water is reabsorbed.AQA
Osmosis: The diffusion of water across a partially permeable membrane from a dilute solution (higher water potential) to a concentrated solution (lower water potential).AQA, OCR
Osmosis and cell function: Water moves into or out of cells by osmosis across the partially permeable cell membrane, and if cells lose or gain too much water they do not function…AQA
osmosis and water uptake: Water enters down a water potential gradient across a partially permeable membrane, as cell sap maintains a lower water potential than soil moisture.OCR
osmotic challenges: High sweating, dehydration, excess water intake and high salt intake are challenges to which the body responds by altering thirst and antidiuretic hormone…OCR
Outcompetition: When one species outcompetes another for food, light, space or mates, the weaker population may fall below the number needed to breed successfully.AQA
Ovary: The organ that is the main site of oestrogen production in females.AQA
Overfishing: Catching fish faster than the populations can reproduce, which is the main cause of fish stock decline.AQA
Ovulation: The release of a mature egg from a follicle in the ovary, occurring around the middle of the menstrual cycle.AQA, OCR
oxygen bubble counting: Quantifying oxygen gas released from the cut stem by counting bubbles produced per minute or collecting gas in an inverted measuring cylinder or gas syringe.OCR
oxygen bubbles: Gas released from the cut stem as photosynthesis occurs, which can be observed and counted over a specified observation period.OCR
Oxygen debt: Produced when anaerobic respiration in muscle converts glucose to lactic acid, and it must be repaid after exercise by continued fast breathing and heart rate.AQA
Oxygen Debt (EPOC): The amount of extra oxygen needed after exercise to break down lactic acid that has built up in the muscles.OCR
Oxygen debt and recovery after exercise: The conversion requires oxygen, linking this process to the oxygen debt and explaining why breathing and heart rate stay elevated after exercise stops.AQA
Oxygen supply and aerobic respiration: Less oxygen reaches the cardiac muscle, so aerobic respiration is limited and the muscle cannot contract as effectively.AQA
Oxygen transport: Red blood cells are adapted for oxygen transport because their biconcave shape gives a large surface area for diffusion and the absence of a nucleus leaves…AQA

P

Painkillers: Medicines that relieve symptoms such as pain, fever or inflammation but do not kill pathogens.AQA
Palisade mesophyll: Cells containing many chloroplasts and positioned near the upper leaf surface, increasing light absorption for photosynthesis.AQA
pancreas: The organ whose beta cells in the islets of Langerhans detect an increase in blood glucose and secrete insulin.AQA, OCR
parallax error: An error when reading liquid levels in graduated syringes or gas syringes without aligning the eye horizontally with the meniscus.OCR
Paralysis: A condition in which damage to nerve cells in the spinal cord may be irreversible.AQA
parasitism: A relationship where the parasite lives in or on a host organism, obtaining nutritional benefit while causing harm.AQA, OCR
Partially permeable membrane: A membrane that lets small water molecules pass while blocking larger solute molecules.AQA
Partially permeable membranes: A membrane through which water diffuses from a dilute solution to a concentrated solution during osmosis.AQA
Passive transport: Diffusion is a passive process because the membrane does not need to provide energy for this movement.AQA
Passive transport and random molecular movement: Osmosis needs no energy from respiration and happens because water molecules move randomly.AQA
Passive versus controlled loss: Losses from the lungs and skin are uncontrolled, whereas the kidneys are responsible for the controlled loss of water, ions, and urea by adjusting urine…AQA
Pathogen: A microorganism that causes disease, including fungi, bacteria and viruses causing diseases like potato blight.AQA
Pathogen classification: Identifying the pathogen type helps explain the disease symptoms and the methods used to control it.AQA
Pathogen dispersal: Fungal pathogens release spores as their dispersal stage, and these are carried through the environment by water or wind.AQA
Pathogen diversity: Plants can be infected by a range of viral, bacterial and fungal pathogens as well as by insects.AQA
pathogen load: The number of pathogens involved, which influences the likelihood and severity of developing an infectious disease.OCR
Pathogen mechanisms: A virus attaches to a specific host cell, injects its genetic material, and uses the cell's machinery to make copies of its own genetic material and protein…AQA
Pathogen reproduction: Bacteria and viruses may reproduce rapidly once inside the body, increasing in number quickly.AQA
Pathogens: Biological agents including viruses, bacteria, fungi, and protists that cause infectious illnesses which can spread between individuals.AQA, OCR
Pathogens as triggers of indirect health effects: A pathogen is the initial trigger, while the cancer or allergy that follows is a consequence, so the causal sequence must be stated clearly.AQA
Patients: People who have the target condition, used later to see whether the drug actually works and whether benefits outweigh side effects.AQA
pedigree charts: Charts that show inheritance traced through shaded and unshaded symbols across numbered generations.OCR
Peptide bonds: The bonds joining amino acids together in proteins, which are polymers of amino acids.AQA
Peptidoglycan: A polymer of sugars and amino acids that bacterial walls are made of, unlike the cellulose walls of plant cells.AQA
percentage change: Calculated as ((final mass − initial mass) / initial mass) × 100, standardising results because pieces cannot be cut to identical starting masses.OCR
Percentage change calculations: Working out the change in mass compared with the starting mass, using (change in mass ÷ initial mass) × 100.AQA
percentage change in mass: Calculated as ((final mass - initial mass) / initial mass) multiplied by 100, accounting for variation in initial cylinder sizes.OCR
percentage gain and loss of mass: A positive value indicates net water uptake, while a negative value indicates water loss.OCR
percentage mass: Calculated by dividing the change in mass by the initial starting mass and multiplying by one hundred percent.OCR
percentage mass loss: A mass potometer measures mass loss over time; percentage loss of mass is calculated as ((initial mass − final mass) / initial mass) × 100.OCR
percentile: The value below which a given percentage of observations fall, summarising the spread of replicate data and helping identify outliers.OCR
percentiles: Values that divide an ordered dataset into one hundred equal parts, providing a standard measure of relative position within a biological distribution.OCR
Peripheral nervous system: The network of nerves connecting receptors and effectors to the CNS.AQA
Permanent vacuole: A fluid-filled space bounded by a membrane, filled with cell sap, which helps keep the cell firm by maintaining internal pressure.AQA
Permeability: The property of cell membranes that insulin increases, so glucose moves from the blood into the cells.AQA
Permeability of kidney tubules: When ADH concentration in the blood increases, the tubules become more permeable to water; when it decreases, they become less permeable.AQA
perpendicular diameter averaging and area calculation: Mean diameter is calculated from perpendicular measurements and zone area is determined using the equation Area = πr².OCR
personal protective equipment: Safety goggles and heat-resistant gloves that prevent scalds and chemical splash injuries when handling hot glassware.OCR
personalised medicine: Drug selection and dosages are targeted to a patient specific genetic profile, optimising therapeutic efficacy while minimising adverse drug reactions.OCR
Pest: An organism that damages crops or livestock, such as locusts, which consume leaves and grains.AQA
pest resistance: A beneficial trait conferred by introducing a foreign gene, such as insect resistance from the Bt toxin.OCR
pesticides: Chemical pesticides control weeds and crop pests.OCR
pH and enzyme activity: Pancreatic and intestinal enzymes work best at around neutral to slightly alkaline pH, and acidity would reduce their activity.AQA
pH buffer control: Adding specific buffer solutions to regulate and maintain constant pH across experimental treatments.OCR
phagocytosis: The process by which phagocytes engulf pathogens and fuse with lysosomes containing digestive enzymes to destroy them.AQA, OCR
pharmacogenomics: Genomic insight underpins the targeting of drug selection and dosages to a patient specific genetic profile.OCR
Phenotype: A characteristic of the organism, such as fur colour, enzyme activity or disease resistance, which changes only if the altered protein changes it.AQA, OCR
phenotypic consequences: Most mutations have no effect on the phenotype, some influence phenotype and a very few determine phenotype.OCR
phenotypic ratios: The theoretical ratio of dominant to recessive phenotypes from a cross between two heterozygous organisms is 3 to 1.OCR
Phloem: Tissue containing living cells with sieve plates, in which dissolved sugars are translocated from sources such as leaves to sinks such as roots and growing…AQA
photolysis: In the first light-dependent stage, light energy absorbed by chlorophyll splits water molecules, releasing oxygen gas as a byproduct while generating ATP and…OCR
Photosynthesis: The process in which carbon dioxide and water are converted into glucose using light energy, so that organisms manufacture food rather than consuming it.AQA, OCR, Pearson Edexcel
Photosynthesis and plant nutrition: Shading and crowding reduce photosynthesis and growth, and mineral ions such as nitrate and magnesium are needed for healthy growth.AQA
photosynthesis graphs: Graphs from which numerical data is extracted accurately, and from which extracted values are used to calculate rates and percentage changes.OCR
Photosynthetic organisms: Organisms, including plants, algae and some bacteria, that capture light energy and use it to convert carbon dioxide and water into glucose and oxygen.AQA
photosynthetic rate: Calculated as volume of oxygen produced divided by time taken, and expressed with appropriate compound units such as cm³ min⁻¹ or cm³ s⁻¹.OCR
Phototropism: A directional growth response to light, in which auxin accumulates on the shaded side of shoots and promotes elongation towards light.AQA, OCR
Physical versus chemical digestion: Emulsification is a physical process, not chemical digestion, because no covalent bonds in fat molecules are broken.AQA
Physical well-being: Having a healthy body that functions properly, free from illness and injury.AQA
physiological units: Compound units such as beats min⁻¹ or cm³ s⁻¹ used to express physiological rates with dimensional consistency.OCR
Pioneering scientific work: Alfred Wallace did much pioneering work on speciation, linking geographical isolation, variation and natural selection to the formation of new species when…AQA
Pituitary control: The pituitary gland detects the level of thyroxine in the blood and releases thyroid stimulating hormone (TSH).AQA
placebo: An inert substance containing no active medicine, used in double-blind trials for comparison against the drug.OCR
Plant and microorganism extracts: Active compounds obtained from roots, leaves, bark or flowers of plants, and from moulds and bacteria.AQA
Plant coordination: Auxin is a plant hormone made in the shoot and root tips that moves away from the tip and can spread unevenly when a plant is stimulated by light or gravity.AQA
Plant disease causation: Viruses, bacteria, fungi and insects can all cause disease or damage in plants.AQA
Plant disease control: Reducing wind movement and avoiding overhead watering can limit dispersal and reduce disease spread, which is why growers improve ventilation and space plants…AQA
Plant growth: Something that is reduced when the plant has less glucose, which it uses for respiration, growth and making new cells.AQA
Plant growth and deficiency symptoms: Proteins are essential for plant growth, so a lack of nitrate ions leads to stunted growth due to reduced protein synthesis.AQA
plant hormones: Several distinct classes that interact to coordinate growth and life-cycle events in plant development.OCR
Plant organ system: The roots, stem and leaves form a plant organ system for transport of substances around the plant.AQA
Plant stem cells: Unspecialised cells in meristems that can divide and differentiate into any plant cell type.AQA
Plant structure and growth: Glucose is used to produce cellulose, which strengthens the cell wall, and to produce amino acids for protein synthesis.AQA
Plasma: The liquid that transports dissolved carbon dioxide, digested food, urea, hormones and heat around the body.AQA
Plasmids: Small rings of DNA, separate from the main DNA loop, of which there may be one or more, or none at all.AQA
plateau: The flat part of the curve where light is no longer limiting, so another factor now controls the rate.AQA
plateau region: On the plateau region the rate remains constant despite further increases, indicating that a factor other than the one on the x-axis is limiting rate.OCR
plateaus: Graphical features that indicate a transport mechanism has reached maximum capacity.OCR
Platelets: Cell fragments that cause blood to clot at a wound, reducing blood loss and helping prevent infection.AQA
platelets and blood clotting: Small, non-nucleated cell fragments that initiate the clotting cascade on blood vessel damage, producing insoluble fibrin protein meshes that trap red blood…OCR
Plot and draw appropriate graphs: Using a line graph with a line of best fit for continuous data and a bar chart for discrete categories, with the independent variable on the x-axis and the…AQA
Pluripotency: The property of human embryonic stem cells that means they can differentiate into most different types of human cells.AQA
pluripotent: Describes embryonic stem cells, which possess the capacity to differentiate into virtually any specialized cell type in the organism.OCR
pluripotent versus multipotent: Embryonic stem cells are pluripotent and can differentiate into any cell type, whereas adult stem cells are multipotent and form limited tissues such as blood…OCR
Poisons: Chemical defences that deter herbivores which would otherwise eat the plant and create entry wounds.AQA
Pollination and seed dispersal: Dependencies in which animals transfer pollen between flowers as they feed, and animals carry, bury or eat and drop seeds.AQA
Pollution: The harm caused when waste and chemical materials are not properly handled and are released into the environment.AQA
pollution standards: Statutory environmental pollution thresholds used to evaluate compliance, assessed using percentiles.OCR
polygenic inheritance: Involves multiple distinct genes situated across different chromosomes exerting cumulative, additive effects on a single physical characteristic.AQA, OCR
polymer: A long chain of sugar units, such as starch, cellulose or glycogen, built from glucose monomers.AQA, OCR
polynucleotide strands: Two separate strands whose outer scaffolding is composed of alternating deoxyribose sugar and phosphate units.OCR
polypeptide polymers: Long chains formed when ribosomes link amino acid monomers in specific sequences.OCR
pondweed experiment: Using an aquatic plant such as Elodea or Cabomba submerged in a beaker of water containing sodium hydrogencarbonate, which supplies a continuous concentration…OCR
population curves: Graphs showing population growth with lag, exponential, stationary and death phases.OCR
population growth: An increasing birth rate raising the population size, so that a larger population needs more food in total.AQA, OCR
Population growth and resource demand: Rapid growth in the human population increases the total demand for resources such as food, water, energy and materials.AQA
population size estimation: Total population size is calculated by multiplying mean count per quadrat by total habitat area divided by quadrat area.OCR
Populations and species: A population is all the organisms of one species in a habitat, so evolution is measured in populations, not individuals.AQA
Position of a mutation: The effect depends on where in the gene it occurs and whether the changed amino acid affects the protein's folding or active site.AQA
Potometer: Measures water uptake by a shoot, which is used as an approximation of transpiration rate.AQA
potometer calculations: For a bubble potometer, rate of movement is distance moved by the air bubble divided by time taken, and volumetric rate is πr²d divided by t.OCR
potometer investigations: A leafy shoot is cut underwater and fitted into the apparatus using an airtight rubber bung to prevent air entering xylem vessels.OCR
Practical investigation of photosynthesis: Activity in which apparatus and techniques are used to investigate photosynthesis, covering AT 1, 2, 3, 4 and 5.AQA
Practical laboratory skills: The loop is passed through a flame until red hot, then cooled before picking up the microorganism, and the lid is secured with tape but not sealed completely…AQA
Practical microscopy skills: Preparing slides and using a light microscope to observe plant and animal cells, starting on the lowest power objective and focusing with the coarse then fine…AQA
Practical technique and safety: Using techniques for the observation and measurement of biological changes, and ensuring the safe and ethical use of human subjects when measuring…AQA
pre-equilibration of biological reagents: Placing enzyme and substrate solutions into separate boiling tubes and keeping them in the water bath for at least 5 minutes before mixing, so the reaction…OCR
Preclinical testing: Takes place in laboratory settings, assessing the chemical on isolated human cells, cultured tissues, and live animals to determine basic efficacy, toxicity,…AQA, OCR
Predator: A consumer that hunts, kills and eats other animals.AQA
predator-prey cycles: Cyclical population changes showing a characteristic time lag between predator and prey peaks.OCR
Predator-prey population dynamics: Repeating cycles in which predator numbers rise and fall after prey numbers, with the peaks and troughs of the two populations out of step.AQA
Predicted versus actual outcomes: Predicted ratios describe chance, not guaranteed outcomes in a particular family, so predicted ratios may not match actual family results.AQA
predicting offspring phenotypes: Translating the resulting genotypes into phenotypes to predict theoretical outcomes, expressed as simplified ratios, percentages, or decimal probabilities.OCR
predictive genetic screening: Screening for specific mutations allows predicting an individual lifetime likelihood of developing non-communicable illnesses.OCR
pregnancy testing and hCG: Mobile monoclonal antibodies linked to coloured dye particles bind the hormone hCG present in pregnant urine, and the complexes bind immobilised antibodies to…OCR
Preparation for division: Growing and increasing the number of sub-cellular structures so that each daughter cell receives enough machinery to function.AQA
Presentation of qualitative results: Presenting results in a suitable table with columns for the food sample, the test or reagent used and the observed result.AQA
Prevention of infection: Because antibodies are produced quickly, pathogen numbers are controlled before symptoms develop, preventing infection.AQA
Prevention strategies: Preventing mosquitoes from breeding means removing or treating standing water where they lay eggs, and mosquito nets act as a physical barrier that reduces…AQA
Preventive control measure: A measure applied to the poultry population rather than a treatment for infected birds, breaking the chain of transmission and controlling the spread of the…AQA
Primary consumers: Herbivores that feed on producers, so they are the first consumers in the chain and occupy level 2.AQA, OCR
Principles of asexual and sexual reproduction: You should be able to apply the principles of asexual and sexual reproduction to an unfamiliar organism when given appropriate information.AQA
Probability: The theory that predicts the chance of each outcome, describing chance rather than certainty, so predictions are about expected proportions in large numbers…AQA
Producer: An organism that makes its own organic nutrients, usually by photosynthesis, and synthesises molecules such as glucose.AQA
Producers: Autotrophs such as green plants and algae that synthesise complex organic molecules from carbon dioxide and water using radiant solar energy via photosynthesis.AQA, OCR, Pearson Edexcel
Products of anaerobic respiration: In human muscle cells glucose is converted to lactic acid, while in plant and yeast cells glucose is converted to ethanol and carbon dioxide.AQA
progesterone: Secreted by the corpus luteum after ovulation, it maintains the thickened uterus lining so that a fertilised egg could implant.AQA, OCR
Prokaryotic cell structure: Bacterial cells are prokaryotic cells and are much smaller in comparison with eukaryotic cells.AQA
Prokaryotic DNA: Genetic material that is not enclosed in a nuclear membrane and lies free in the cytoplasm.AQA
Proportional: Each bar width correctly represents the biomass data, so bars of equal width regardless of the values are inaccurate.AQA
Proportional representation: Each level is drawn as a horizontal bar whose width is proportional to the biomass present, using a consistent scale.AQA
prostate cancer and PSA: Fluorescently tagged monoclonal antibodies detect disease biomarkers such as prostate-specific antigen in blood tests to diagnose prostate cancer.OCR
Proteases: Produced in the stomach, the pancreas and the small intestine, they act on proteins, breaking them down to amino acids.AQA
Protection and regeneration of rare habitats: Conserving existing areas and restoring damaged ones, for example by replanting native vegetation or removing invasive species.AQA
Protection from harm: Reflex actions protect the body from harm, and their speed can prevent injury.AQA
Protection of intestinal tissue: Neutralisation protects the lining of the small intestine from acid damage and provides suitable conditions for enzymes.AQA
protein breakdown: Hydrolysis of polymer chains back into free amino acid monomers, releasing them for cell growth, repair, or enzyme synthesis.OCR
protein folding: The amino acid sequence dictates how the polypeptide chain folds into a unique three-dimensional shape, which in turn determines the protein's function.AQA, OCR
Protein folding and function: A changed amino acid sequence can alter the folding and shape of the protein, and a protein with a changed shape may have altered function.AQA
Protein function: The particular job of a protein, such as an enzyme or a structural protein, which depends on how the chain folds.AQA
Protein structure: When a protein chain is assembled, it folds up into a unique three-dimensional shape that is essential for carrying out its specific function.AQA
protein synthesis: The DNA base sequence of a gene is copied into a messenger molecule, which carries the code to a ribosome where amino acids are joined in the correct order to…AQA, OCR
Protein synthesis and folding: The sequence of amino acids determines how a polypeptide folds into its three-dimensional shape.AQA
Protist: A single-celled eukaryotic microorganism with a nucleus and other membrane-bound organelles, not a bacterium, virus or fungus.AQA
Protists: Mostly single-celled eukaryotes, some of which are parasites transmitted by vectors.AQA
Provisional and changing scientific models: Each new model is a hypothesis that fits the available evidence, and when evidence grows the model is revised or replaced.AQA
Puberty: The stage of development when the reproductive system becomes mature, triggered by hormones released by the pituitary gland.AQA
Public health and treatment adherence: Completing the prescribed course maintains the antibiotic concentration long enough to kill even bacteria with partial resistance, reducing the chance that…AQA
Publication and scientific debate: On the Origin of Species was published in 1859, and many scientists and religious leaders debated the work.AQA
Pulmonary circuit: The circuit in which the right side pumps deoxygenated blood to the lungs and back to the left side.AQA
pulmonary circulation: The circuit in which the right ventricle pumps deoxygenated blood under low pressure to the lungs and it returns to the left atrium.OCR
Punnett square: A grid that shows every possible combination of alleles from two parents, with one parent's gametes across the top and the other's down the side.AQA
Punnett squares: Visual matrices used to model the random segregation and combination of alleles during sexual reproduction.OCR
pupillary reflex: Circular and radial antagonistic smooth muscles in the iris alter pupil diameter to regulate light entry during the pupillary reflex.OCR
Purification: The antibody-containing liquid is processed to separate the antibody from cells, nutrients and other substances so that only the required antibody remains.AQA
Pyramid of biomass: A quantitative diagram in which each trophic level is drawn as a horizontal bar whose area is proportional to the dry mass of living material present.AQA
pyramids of biomass: Always upright, showing the decrease in biomass at each successive stage and the direction of energy flow.AQA, OCR
Pyramids of biomass and numbers: A representation of the decrease between trophic levels, with the producer level usually the largest.AQA

Q

quadrat and transect methodology: Quadrat frames placed at random coordinates estimate population sizes of sessile organisms, while line or belt transects laid across an environmental gradient…OCR
Qualitative food tests: Using iodine reagent as a qualitative test for starch and interpreting the colour change.AQA
Qualitative identification of biological molecules: The tests are qualitative, so they show whether a substance is present rather than giving an exact concentration.AQA
qualitative reagents: Substances used to identify biological molecules by colour changes, such as Benedict's reagent, iodine solution, Biuret reagent and the ethanol emulsion test.OCR
Quantitative interpretation of osmosis data: Reading a positive percentage change as water entering the tissue by osmosis and a negative percentage change as water leaving.AQA
Quantitative measurement: Using a ruler to measure shoot and root length in millimetres from the base of the shoot or root to the tip, recording values in a table with units.AQA
Quantitative measurements: Recordings such as cell length or estimates of cell size using the field of view, rather than just general observations.AQA
quarantine and vaccination: Preventative measures in animals that include quarantine of infected cases and mass vaccination to achieve herd immunity.OCR

R

Random motion: The way particles move randomly in all directions, which causes them to spread from where they are more concentrated.AQA
Random nature of mutation: Mutation is a random change in the base sequence of DNA.AQA
random sampling: Uses grid coordinates generated by random number tables to position quadrats, preventing investigator bias in uniform environments.AQA, OCR
Random sampling to avoid bias: Placing quadrats at random positions, for example using random number coordinates, so that bias is avoided.AQA
Randomness of mutation: Mutation can happen in any cell at any time and is not directed by need.AQA
Rapid automatic responses: Reflex actions are rapid, automatic responses that do not require conscious thought.AQA
Rapid coordination: Features of the nervous system allow fast, targeted coordination of behaviour.AQA
Rapid population growth: Asexual reproduction is faster than sexual reproduction, allowing rapid population increase.AQA
Rate: A compound measure that compares a quantity with time.AQA
rate against distance graph: A graph whose shape the law predicts, rising steeply as distance decreases.AQA
rate calculation: Rate is calculated as distance moved divided by time (mm s⁻¹) or volume using πr²d / t (mm³ s⁻¹).OCR
rate calculations: Applying mathematical equations to experimental and anatomical data in transport systems, such as dividing distance by time or multiplying heart rate by…OCR
rate graph: A graph of rate against light intensity that rises steeply, then flattens into a plateau.AQA
Rate of blood flow: Volume of blood divided by time taken, or distance travelled by blood divided by time taken.AQA
rate of decay: Calculated by dividing the change in a measured quantity by the time taken, for example mass lost ÷ time or gas produced ÷ time.AQA, OCR
rate of photosynthesis: Measured by counting oxygen bubbles per minute or by collecting the gas volume.AQA
Rate of reaction: The rate of photosynthesis rises as light increases, stays constant at a plateau when another factor limits it, and can be raised by temperature only up to an…AQA, OCR
Rate of starch digestion: Shown by the time taken for the iodine test to become negative, as samples are tested every 30 seconds.AQA
Rate of transpiration: A compound measure because it compares an amount of water lost with the time taken.AQA
rate of transport: A compound measure of physical or biological change per unit time, such as the rate of water uptake in a plant stem.OCR
Reabsorption: Water is reabsorbed from the filtrate back into the blood, and the amount reabsorbed determines urine concentration and volume.AQA
Reabsorption of glucose: Movement of glucose from the tubule back into the blood, so that it is completely reabsorbed and absent from the final urine.AQA
reaction rate: A compound measure expressing the velocity of biochemical transformations, expressed in units like cm³ s⁻¹, g min⁻¹, or s⁻¹.OCR
reaction rates: How rapidly reactants disappear or products accumulate over time, calculated as volume of product formed or mass of substrate broken down divided by time taken.OCR
reaction time: A smaller time value indicates a faster response, and it can be measured in milliseconds on a computer screen.OCR
Rearranging the equation: Allows calculation of volume (rate × time) or time (volume ÷ rate).AQA
Receptor: Detects a stimulus, such as a sharp pinprick, and generates an electrical impulse in a sensory neurone.AQA
Receptor-hormone binding: When the hormone binds to its receptor, it triggers a specific response.AQA
Receptor–coordination centre–effector framework: A receptor detects a stimulus, a coordination centre processes the information, and an effector responds, and both routes share this same three-part framework.AQA
Receptors: Cells which detect stimuli, which are changes in the environment.AQA
Recessive allele: An allele that is not expressed when a dominant allele is present, as with fur colour in mice where the dominant allele is expressed over it.AQA
Recombinant DNA: Formed when DNA ligase joins the gene into the vector.AQA
recombinant insulin: Recombinant bacteria engineered with human genes produce abundant, pure therapeutic proteins, such as human insulin for diabetes.OCR
Recording and presenting data: Recording measurements in a table with clear headings, units and repeated readings over time, and using drawings alongside measurements to describe the…AQA
Recruitment: The production of young fish, which collapses if fishing removes most large adults before they can spawn.AQA
Recycling of matter: Materials in the living world are recycled rather than used up, passing between organisms and the environment.AQA
Recycling resources: Using resources again rather than dumping waste in landfill, which reduces pollution and the extraction of raw materials.AQA
Red blood cells: Cells suspended in plasma that contain haemoglobin, which binds oxygen in the lungs and releases it in tissues, and have no nucleus to maximise space for…AQA
Reduced species dependence: The mechanism linking high biodiversity to ecosystem stability, because many species perform similar roles so the loss of one species has less impact.AQA
Reducing harm to healthy cells: Healthy cells lack the antigen, so they are not targeted and are largely spared, which reduces damage to normal tissue.AQA
reduction division: Halving the chromosome number is crucial so that when two haploid gametes fuse during fertilisation, the resulting zygote restores the full diploid chromosome…OCR
Reduction in mortality from infection: Deaths from infectious bacterial diseases such as tuberculosis and septicaemia have fallen dramatically since the introduction of antibiotics.AQA
Reflex action: Rapid, automatic responses that protect the body, such as withdrawing a hand from a hot object.AQA
reflex arc: A pathway that provides an involuntary, rapid, automatic protective response, passing directly through the spinal cord or unconscious brainstem.AQA, OCR
Refraction: Stronger refraction brings diverging rays from a near object to a focus on the retina.AQA
Regeneration and repair: The difference in differentiation ability helps explain why plants can grow continuously and regenerate parts more readily than most animals.AQA
Regulation of internal conditions: The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.AQA
relative abundance: The amount of a plant or animal species within a quadratted community, expressed as a fraction or percentage of the total community count.OCR
Relay neurone: A neurone inside the spinal cord or brain that links sensory and motor pathways, allowing the impulse to be processed and directed.AQA
reliability: Improved by repeating readings at each distance and calculating a mean.AQA
Reliability and repeat measurements: Collecting repeat readings and calculating a mean to reduce the effect of random variation and improve reliability.AQA
Reliability and sample size: A sample must be large enough so that the estimate is reliable, because larger samples usually give more reliable estimates than very small samples.AQA
Reliability, repeats and control variables: Repeating samples and keeping variables such as quadrat size and sampling method constant to improve reliability.AQA
Removing affected leaves: Physically removing infected tissue, which lowers the number of spores released to reinfect the plant.AQA
Repair: Replacing worn-out or damaged cells, for example healing a cut or replacing skin cells.AQA
Repair and replacement: In mature animals, cell division is mainly restricted to repairing damaged tissues and replacing worn-out or dead cells.AQA
Repeated artificial selection: A repeated cycle carried out over many generations in which individuals showing the desired characteristic are selected and bred together.AQA
Repeated selection over generations: The cycle of selecting parents and breeding them, repeated over many generations.AQA
repeats: Measurements taken at each station so that anomalous field readings can be identified and investigated rather than accepted from a single value.OCR
Replacement lens: An artificial lens implanted inside the eye to correct severe focusing errors.AQA
Representative sample: A sample that reflects the population's key features, such as age, sex and location, so results can be generalised.AQA
representative sampling: Recruiting patient cohorts matched for age, biological sex, and baseline health conditions so findings are unbiased and generalisable to human populations.OCR
Reproduction: In humans, this is controlled by hormones, including FSH, oestrogen, LH and progesterone, which act in sequence during the menstrual cycle.AQA
Reproduction and gametes: The survivors reproduce and so contribute gametes to the next generation.AQA
Reproductive isolation: Modern genetics explains how mutations create new alleles and how reproductive isolation can arise through changes in mating behaviour, chromosomes or…AQA
Research tools and fluorescent labelling: In research, monoclonal antibodies bind to specific molecules in a cell or tissue with a fluorescent dye so the molecules can be located or identified.AQA
resolution: The ability to distinguish two separate points that are close together, which is greater in electron microscopy because electron beams have a much shorter…AQA, OCR
Resolution and visible detail: Electrons have a much shorter wavelength than visible light, so the resolution limit is far smaller and points that a light microscope merges are seen as…AQA
Resolving power: The smallest separation at which two points can still be seen as separate.AQA
Resource use: Producing export crops can use scarce local resources such as water and fertile land, which may reduce food available locally.AQA
Respiration: The process that provides the energy needed for active transport, and which the absorbed sugar helps to supply glucose for.AQA, OCR
Respiration and biosynthesis: Glucose is used for respiration, and is used to produce amino acids for protein synthesis.AQA
Respiration and carbon return: During aerobic respiration, decomposers release carbon dioxide back to the atmosphere, so carbon is recycled for photosynthesis.AQA
Respiration and energy transfer: The process that releases energy from glucose in cells, and this energy is required for active transport.AQA
Respiration as energy release: Glucose is broken down in cells using oxygen to release energy for processes such as muscle contraction, active transport and building large molecules.AQA
Response to stress: Adrenaline is produced by the adrenal glands in times of fear or stress, increasing heart rate and boosting delivery of oxygen and glucose to the brain and…AQA
Restoring one-way blood flow: The aim of valve replacement, which also reduces the extra workload on the heart.AQA
Restriction enzyme: Cuts DNA at a specific sequence to cut the desired gene out.AQA
restriction enzymes: Enzymes that cut the desired gene from donor DNA and cut open a bacterial plasmid vector, leaving complementary sticky ends.OCR
Retina: The part of the eye on which light rays must focus for a sharp image; in both defects the rays do not focus on it.AQA
Reversibility and long-term suitability: Sterilisation is intended to be permanent, while the pill, implant and barrier methods are generally reversible.AQA
ribosomes: The mRNA binds to this structure in the cytoplasm during translation, where tRNA molecules align complementary anticodons to mRNA codons.AQA, OCR, Pearson Edexcel
Risk assessment and prevention: Because factors interact, disease prevention is complex, and interacting factors can increase risk more than any single factor alone.AQA
Risk assessment in practical work: Recognising hazards such as ethanol being flammable and iodine staining, and taking suitable precautions such as wearing eye protection and avoiding contact…AQA
Risk evaluation: Comparing benefits like convenience against risks such as surgical complications or eye infections.AQA
Risk factor: Something linked to an increased rate or chance of developing a disease, but which does not guarantee disease.AQA
Risk factors: Influences that raise the chance of developing a non-communicable disease, but they are not guarantees.AQA
Risk factors and disease: In risk-factor studies, a positive correlation might link the number of cigarettes smoked per day with the risk of lung cancer, but other factors may be…AQA
Risk factors and disease trends: Describing the overall trend shown, such as an increase, decrease or no clear change, in terms of risk factors.AQA
Risk factors and health: A poor diet causing anaemia reduces oxygen transport, so tissues heal slowly and infection risk rises.AQA
Risk factors and non-communicable disease: Scientists compare disease rates in groups with different exposures, such as smokers and non-smokers, and use samples to estimate how strongly a factor such…AQA
Rod cells: Receptors sensitive to light intensity, working well in dim light but not detecting colour.AQA
Role of enzymes and vectors: Enzymes are used to isolate the required gene, which is then inserted into a vector, usually a bacterial plasmid or a virus.AQA
Role of the immune system: The immune system still has to clear the pathogen when only symptom-relieving medicines are used.AQA
Roles of bacteria and fungi in ecosystems: Obtaining energy and nutrients from dead matter and waste products, and being essential for recycling nutrients.AQA
root hair cell adaptations: A long, narrow cytoplasmic extension that significantly amplifies the surface area in contact with soil water, facilitating rapid uptake.OCR
Rooting powder: A product into which auxins are incorporated, stimulating cut stems to develop adventitious roots rapidly for vegetative propagation.AQA, OCR
Rooting powders: Auxin is applied to the cut end of a stem cutting and stimulates root formation, so the cutting establishes quickly and many identical plants can be produced.AQA
Roots: Absorb water and mineral ions from the soil.AQA
Runners: Horizontal stems sent out by strawberry plants, with new plantlets growing at nodes that can root to form independent plants.AQA

S

safe handling of caustic soda lime: Soda lime used to absorb carbon dioxide is caustic and harmful, so safety goggles and gloves are mandatory and spills must be neutralized immediately to…OCR
safe laboratory heating: Wearing eye protection, securing hot glassware with tongs, and preventing boiling water splash injuries when using heating devices.OCR
Safe practical work: Handling apparatus and reagents safely, including care with hot water, glassware and iodine reagent.AQA
Safe use of apparatus and techniques: Using appropriate apparatus such as test tubes, measuring cylinders, dropping pipettes and a water bath safely and correctly, including heating Benedict's…AQA
safe zone measurement through closed dish: Zone of inhibition diameters are measured through the bottom of the unopened petri dish to the nearest millimetre using a transparent ruler.OCR
Safety and efficacy: Testing checks that a drug does not cause unacceptable harm and that it actually treats the condition.AQA
Safety and ethical practice: Safely and ethically using living organisms to measure responses to the environment, ensuring organisms and habitats are not harmed, including avoiding…AQA
Safety, efficacy and licensing: If results show the drug is safe and effective, it can be licensed and marketed; otherwise development stops.AQA
Salmonella: A bacterium that can cause food poisoning in humans, typically after eating contaminated food such as undercooked chicken or eggs.AQA
sample size and reliability: Adequate sample sizes ensure mean values are reliable, reducing the impact of anomalies.OCR
Sampling: Selecting and studying part of a population to draw conclusions about the whole population, such as the proportion of people exposed to a risk factor.AQA
Sampling and ecological measurement: Applying techniques such as random quadrats or systematic transects to investigate organism distribution, and using apparatus to make accurate measurements…AQA
Sampling and estimation: Counting the chosen species in each quadrat, calculating a mean number per quadrat, and scaling the mean up to the whole area to estimate population size.AQA
saprotrophic nutrition: A process in which microorganisms secrete digestive enzymes externally onto dead organic matter and absorb the soluble nutrients released.OCR
Scale: A suitable scale is chosen so the largest biomass value fits the space available and bar widths are calculated from it.AQA
Scale and cell size: As an object becomes smaller, its surface area falls, but its volume falls much faster, so the ratio of surface area to volume rises.AQA
Scale and consistency of manufacture: Synthesis allows large, consistent quantities to be made.AQA
scale and magnitude: Each step down the scale represents a thousand-fold reduction in size, so 1 mm contains 1000 µm and 1 µm contains 1000 nm.OCR
Scale and measurement in biology: Use the same unit for both cells when comparing, for example convert 0.002 mm to 2 micrometres before stating the ratio.AQA
Scale and size of cells: Cells vary enormously in size, so biologists compare them using orders of magnitude and standard form.AQA
Scale bar: A known scale that a structure can be compared with to estimate its size.AQA
scale selection: Choosing sensible, linear numerical scales that allow plotted points to occupy at least half of the graph paper.OCR
scaling laws: As an organism increases in linear dimensions, volume expands as the cube of length while surface area increases only as the square.OCR
scaling up: Multiplies mean count per quadrat by total habitat area divided by quadrat area to estimate total plant population.OCR
Scatter diagram interpretation: Reading the pattern of points on a scatter diagram, where one variable is on the x-axis and another on the y-axis, to identify positive, negative or no…AQA
scatter diagrams: Graphs that plot paired health variables to evaluate relationships between lifestyle risk factors and disease incidence.OCR
scientific acceptance: Mendel findings were not accepted during his lifetime because he could not explain the physical mechanism behind his factors.AQA, OCR
Scientific drawing and labelling: Drawing what you see using clear, unbroken lines without shading, and labelling visible structures accurately.AQA
scientific drawing conventions: Biological drawings use unbroken pencil lines, no shading, accurate proportions, and state the total magnification, with straight, uncrossed label lines…OCR
Scientific evidence and causation: Because factors interact, it is difficult to prove that one factor alone causes a disease, which makes causal proof complex.AQA
Scientific publication: The sharing of scientific ideas so that they are checked and made known, as when joint writings were published in 1858.AQA
Scientific uncertainty and hypotheses: Several plausible ideas remain hypotheses rather than certainties, because the events cannot be repeated or directly observed.AQA
Scientific understanding of inheritance and variation: Understanding the human genome matters scientifically because it shows how genes work and how humans compare with other species.AQA
sclera: The tough, white outer coat that protects the eye and maintains its shape.AQA
Seasonal change: Regular, predictable cycles such as changing day length, temperature or rainfall across the year.AQA
Secondary bacterial infection: Antibiotics may be given only if a secondary bacterial infection develops.AQA
secondary consumer: A carnivore at level 3 that eats herbivores, which are the primary consumers at level 2.AQA
Secondary sex characteristics: Features such as voice deepening, facial hair growth, breast development and widening of the hips that develop during puberty.AQA
Secondary sexual characteristics: Female features promoted by oestrogen at puberty, such as breast development and widening of the hips.AQA
Secondary tumours: A tumour that forms at a new site is a secondary tumour.AQA
seed germination: Involves breaking seed dormancy and the synthesis of amylase enzymes, which gibberellins play key roles in promoting.OCR
seedbanks and genetic resources: Store viable seeds in cold, dry conditions to protect rare alleles against extinction, habitat loss and climate change.OCR
seedless fruit: Produced by spraying gibberellins to induce parthenocarpic development in unpollinated flowers.OCR
Selecting appropriate scales for axes: Choosing a scale for each axis that covers the full data range, uses equal intervals and makes efficient use of the available grid so points are clearly…AQA
Selection and survival: Successful competitors survive and reproduce, so competition acts as a selection pressure within the community.AQA
Selection of parents by humans: Humans identify and choose individuals that show the desired characteristic as parents, while those without it are not allowed to breed.AQA
Selection pressure: A named environmental factor, such as predators or antibiotics, that favours phenotypes best suited to the environment.AQA
Selection pressures in the environment: The environment presents a selection pressure, such as predation, disease or competition for resources, and the environment does the selecting, not the…AQA
Selective action on bacterial cells: Antibiotics work only on bacteria because they target bacterial structures, for example the cell wall or bacterial ribosomes, which human cells do not have.AQA
selective breeding: Humans deliberately choosing individual animals or plants exhibiting desirable traits to breed together, repeating across many successive generations until…AQA, OCR
Selective filtration in the kidney: Filtration in which substances pass into the kidney tubule based on molecule size, with large molecules such as proteins retained in the blood.AQA
selective herbicides: Synthetic auxins formulated to make broad-leaved weeds absorb higher quantities than narrow-leaved cereal crops, inducing uncontrolled rapid growth that…OCR
Selective reabsorption: The process that returns useful substances to the blood, including all of the glucose, some ions and some water, while urea and excess ions and water remain…AQA
selective reabsorption in the proximal convoluted tubule: The process in which all glucose, amino acids and some salts are returned to the blood.OCR
Selective toxicity of medicines: Because a virus is inside human cells, a medicine that attacked it could also harm the host cells.AQA
Selective weed killer: An auxin-based agricultural use that reduces competition from broad-leaved weeds in cereal fields, improving yield.AQA
Selective weed killers: Synthetic auxins are sprayed onto fields, and broad-leaved weeds absorb them and grow abnormally, while narrow-leaved cereals are less affected.AQA
Selectivity of drug action: Antiviral drugs must be highly selective, which is difficult because viruses rely on the host's own cellular processes.AQA
Self-renewal: Division by mitosis to produce more stem cells of the same type, so the supply is maintained.AQA
Sense organ: A group of receptor cells that detect a specific stimulus.AQA
sensory receptors: Specialised structures throughout the body that detect distinct forms of energy and transduce stimuli into electrical impulses.OCR
Sequential numbering of feeding positions: Once level 1 is fixed as the producer, every later feeding step is numbered by adding one.AQA
sex chromosomes: The 23rd pair of chromosomes in humans, which determines biological sex.OCR
Sex determination: Sex is determined at fertilisation by the sperm: an X-bearing sperm gives a female and a Y-bearing sperm gives a male.AQA, OCR
Sexual reproduction: Involves gametes and fertilisation, producing genetic variation in offspring, which improves survival if the environment changes, but requires two parents,…AQA, OCR
Shivering: Skeletal muscles contract rapidly and repeatedly, and the increased respiration in muscle cells releases energy as heat.AQA
Short diffusion distance: The diffusion distance is short because the cell is small, so molecules do not have far to travel and supply to the cytoplasm is fast enough.AQA
Short sight: A defect in which the image forms in front of the retina, often because the eyeball is too long or the lens is too strong.AQA
Side effects and tissue damage: Damage to body tissues can occur because the drug's action may disrupt normal host cell functions.AQA
sieve tube elements: Living phloem cells arranged end-to-end with perforated sieve plates, lacking nuclei to facilitate flow of sap.OCR
signal integration: The processing of multiple neural inputs within the brain or spinal cord, where inputs are integrated and evaluated against stored information.OCR
silent mutations: Changes that do not alter amino acid sequences or protein functionality, producing no phenotypic change.OCR
Simple ratios: Compare parts with each other, such as 3:1, and should be kept in their simplest whole-number form.AQA
Single-gene inheritance: Some characteristics are controlled by a single gene, such as fur colour in mice and red-green colour blindness in humans.AQA
Sink: A region that uses or stores sugars, such as a growing tip, root, fruit or storage organ.AQA
Skin: Acts as a physical barrier, with an outer layer of dead cells that is tough, and glands that secrete antimicrobial substances.AQA
skin barrier: Forms an unbroken, tough physical barrier covered in sebum with antimicrobial properties and shedding dead surface cells.OCR
Slime capsule: An additional layer found outside the wall in some bacteria.AQA
Social issues: Points such as reducing suffering in families, giving parents informed choice, and the possible emotional or social pressure to use screening.AQA
socioeconomic conflicts: Conservation goals often conflict with local farming needs, and major socioeconomic challenges impede conservation.OCR
sodium hydrogen carbonate solution: A dilute solution in which a freshly cut pondweed stem is submerged so that it supplies an excess of dissolved carbon dioxide.OCR
sodium hydrogencarbonate: A substance in the water that supplies a continuous concentration of dissolved carbon dioxide.OCR
soil moisture: Measured with electronic resistance probes or gravimetrically by weighing a soil core, drying it in an oven to constant mass and calculating percentage water…OCR
somatic cells: Normal body cells, which are diploid, containing 46 chromosomes in 23 pairs.OCR
Source: A region that produces or releases sugars, such as a mature leaf carrying out photosynthesis.AQA
Sources of genetic variation: New alleles appear continually through mutation, providing the genetic variation on which natural selection can act.AQA
Specialisation of cells and organs: Surfaces and organ systems are specialised for exchanging materials to allow sufficient molecules to be transported into and out of cells.AQA
Specialised animal cells: Cells in animals that may be specialised to carry out a particular function, such as sperm cells, nerve cells and muscle cells.AQA
Specialised cell: A cell with distinct structures and functions, so that tissues and organs can carry out jobs efficiently.AQA
specialised cells: Cells that develop the structure needed for their function, such as muscle cells, nerve cells, red blood cells, xylem vessels and palisade mesophyll cells.AQA, OCR
Specialised plant cells: Cells in plants that may be specialised to carry out a particular function, such as root hair cells, xylem and phloem cells.AQA
speciation: Populations that become separated accumulate different variations and over many generations may become so different that they can no longer interbreed to…AQA, OCR
Speciation and reproductive isolation: If populations become so different, or are separated so they can no longer interbreed to produce fertile offspring, a new species may form.AQA
Species: The second part of a binomial name, written with a lower-case letter, which identifies one specific kind of organism.AQA
species conservation: Positive human interactions preserve biodiversity through initiatives including designating nature reserves, breeding endangered animals in captivity for…OCR
Species distribution: Where species are found within an ecosystem, which shifts when environmental changes force organisms to move to more suitable areas or die out locally.AQA
species distribution shifts: Movements of species ranges toward polar latitudes or higher altitudes, with range contractions in alpine species, caused by rising atmospheric carbon dioxide…OCR
Species richness: The number of species in a community, which decreases when pollution removes species.AQA
Specific defence: White blood cells, mainly lymphocytes, recognise antigens on the pathogen surface, and each lymphocyte is specific to one antigen.AQA
Specific immune response: Antibodies and memory cells recognise particular antigens, and memory cells remaining after an infection give a faster, stronger response on re-infection.AQA
Specification scope: Knowledge of reproduction in organisms is restricted to those mentioned in the specification.AQA
specimen preparation: Specimens must be dehydrated and placed in a vacuum, which precludes live viewing.OCR
Sperm production: The process stimulated by testosterone in the testes.AQA
Spinal cord: Carries signals between the brain and the rest of the body and also coordinates some rapid reflexes on its own.AQA
Spongy mesophyll: Has loosely arranged cells with air spaces that let gases diffuse through the leaf.AQA
Spore structure and function: Spores are microscopic reproductive structures released in huge numbers from infected tissue, and being small and light they are the dispersal structure…AQA
Spores: Structures by which fungi spread, carried in air, water or on surfaces, and often entering plants through leaves or wounds.AQA
spotting tile sampling technique: Sampling the reaction mixture into spotting tile wells containing iodine solution at regular 30-second intervals to monitor starch digestion.OCR
Spread in the blood: Cells can break away and travel to other parts of the body in the blood.AQA
Stable community: A community where all the species and environmental factors are in balance, so population sizes stay roughly constant over long periods.AQA
Stages of HIV infection: HIV initially causes a flu-like illness, after which the person may feel well for years while the virus continues to damage immune cells.AQA
staining: Adding a stain to a specimen adds contrast to colourless cells, with iodine staining plant starch blue-black and plant cytoplasm yellow-brown, while methylene…OCR
Standard form: A way of writing a number as A × 10ⁿ, where A is at least 1 and less than 10, and n is an integer.AQA
Statins: Drugs that lower blood cholesterol and reduce fatty deposits; they are usually non-invasive and can be taken long term, but may cause side effects and must be…AQA, OCR
Stem cell: An undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from…AQA
stem cell functions: Division to produce a range of different cell types for development, growth and repair.OCR
Stem cell therapy: An area of medicine that aims to replace damaged or missing cells, and may be able to help conditions such as diabetes and paralysis.AQA
stem cells: Undifferentiated biological cells that retain the capacity to divide continuously by mitosis and differentiate into specialized cell types.AQA, OCR
Stem cells and immune rejection: Because the embryo's genes came from the patient, the stem cells have the same genes as the patient, reducing the risk that the immune system will reject the…AQA
Stem cells and unspecialised cells: Unspecialised cells capable of differentiating into specific cell types, some of which remain in tissues such as bone marrow.AQA
Stem cells in mature animals: The body relies on specific stem cell populations, such as those in bone marrow, for replacement of certain cell types.AQA
Stent: A small mesh tube inserted into a narrowed coronary artery to hold it open.AQA
stents: Mechanical devices that hold narrowed coronary arteries open; they can be fitted quickly and improve blood flow, but carry surgical risks and may need…AQA, OCR
sterile micropipette: Used to dispense precise volumes of bacterial culture, for example 0.1 cm³, to produce uniform lawns.OCR
Sterilisation and contamination control: All equipment and media are sterilised before use, and all equipment is sterilised after use, to reduce the risk of contamination.AQA
Sterilising: Killing unwanted microorganisms on Petri dishes and culture media before use, preventing contamination and competition with the intended culture.AQA
sticky ends: Short, unpaired single-stranded overhangs left when restriction enzymes cleave staggered palindromic sequences.AQA, OCR
Stimulus: A change in the environment, such as a rise in blood glucose or a drop in skin temperature.AQA
Stimulus and response: Receptors detect stimuli in the surroundings, and the nervous system links this detection to a coordinated response.AQA
Stomach: Produces hydrochloric acid, which is very acidic and kills many swallowed pathogens.AQA
stomach hydrochloric acid: Provides a chemical barrier at pH 1 to 2, denaturing pathogen enzymes and killing ingested microorganisms.OCR
Stomata: Small pores, mostly on the lower surface of a leaf, each surrounded by two guard cells, through which gas exchange and water loss are controlled.AQA, OCR
stomata and guard cells: Microscopic pores bounded by pairs of guard cells, which become turgid in light to open the pore and flaccid in darkness to close it.OCR
stomatal aperture: The opening of the stomata, which light intensity alters by stimulating guard cells to open them wider.OCR
Storage and transport: Fruit is often harvested unripe and exposed to ethene when ripening is required, allowing fruit to be stored and transported without over-ripening.AQA
Storage molecules: Glucose is converted into insoluble starch for storage, or into fat or oil for storage.AQA
Storage of genetic information: The function allowed by the structure, in which the base sequence stores information and the molecule can be copied accurately.AQA
Strain: A variant of the species with different features, such as the ability to resist an antibiotic or to produce a different toxin.AQA
Stress: Prolonged stress can cause physical symptoms such as high blood pressure and increase the risk of mental health issues like anxiety and depression.AQA
structural adaptations: Physical features of the body or surface of an organism, such as the thick fur of a polar bear or the waxy cuticle of a leaf.AQA, OCR
Structural barriers to pathogens: Physical defences that block microorganisms from entering plant tissues or limit their spread once inside.AQA
Structural proteins: Proteins, like collagen, that form strong, fibrous shapes providing structural support in tissues such as skin and bone.AQA
Structural proteins in organisms: A structural protein such as collagen in connective tissue or keratin in skin, hair and nails may lose its strength if a mutation changes its shape.AQA
Structural, behavioural and functional adaptations: Adaptations may be structural, such as a camel's hump storing fat, behavioural, such as migration, or functional, such as producing venom.AQA
Structure and function: The nervous system is adapted to detect changes and coordinate rapid responses, with receptors detecting stimuli and generating electrical impulses.AQA
Structure and function of animal organs: The stomach contains muscular tissue to churn food, glandular tissue to secrete digestive juices, and epithelial tissue to line its inner and outer surfaces.AQA
Structure and function of biological molecules: DNA is a polymer of nucleotides, each containing a sugar, a phosphate group and a base, and two strands form a double helix.AQA
Structure and function of organelles: Observing a structure allows biologists to infer its function, for example ribosomes as sites of protein synthesis.AQA
Structure and function of pathogens: Different pathogen groups have different structures and reproduction methods, which affects how disease spreads and is controlled.AQA
Structure and function of phloem: Phloem is composed of tubes of elongated cells, and cell sap can move from one phloem cell to the next through pores in the end walls.AQA
Structure and function of plant organs: A leaf contains palisade mesophyll tissue for photosynthesis, xylem and phloem for transport, and epidermal tissue for protection.AQA
Structure and function of proteins: A changed amino acid sequence can produce a changed three-dimensional shape and therefore a changed function.AQA
Structure and function of valves: Atrioventricular valves sit between atria and ventricles, and semilunar valves sit between ventricles and the arteries leaving the heart.AQA
Studying patients with brain damage: If damage to a region removes a function, that region is likely to control it.AQA
Stunted growth: When a plant is smaller or grows less than expected for its age and conditions, caused by nitrate deficiency.AQA
Sub-cellular structure and function: Finer structural detail helps biologists link sub-cellular structure to its function more precisely.AQA
Sub-cellular structures: Structures that are too small to see directly, so biologists estimate their size or area from images and known scales.AQA
substance transport: Water is transported to serve as an essential solvent and maintain cellular turgor, blood volume and biochemical reactions.OCR
Substances in the body or environment: Materials the person encounters, such as carcinogens in tobacco smoke, ionising radiation, or chemicals in the air or workplace.AQA
sugar-phosphate backbone: A continuous, alternating structure produced when thousands of nucleotides link covalently along their sugar and phosphate groups.AQA, OCR
superovulation: Induced by higher doses of follicle-stimulating hormone and luteinising hormone, prompting ovaries to develop multiple mature follicles simultaneously for egg…OCR
superweeds: Herbicide-resistant weeds created by the potential outcrossing of resistance genes to wild relatives.OCR
Surface area: Mechanical digestion, such as chewing and churning, increases this for enzyme action, and villi give a large one for efficient absorption.AQA
Surface area and diffusion: Villi and microvilli in the small intestine, alveoli in the lungs, gill filaments and lamellae, root hair cells and a large flat leaf surface all increase…AQA
Surface area and exchange: Absorption happens mainly in the small intestine, whose lining has a large surface area and a good blood supply, features that increase the rate of absorption.AQA
Surface area and rate: A larger surface area means more lipase molecules can contact fat at the same time, so the rate of breakdown rises.AQA
Surface area and rate of reaction: Bile emulsifies lipids into small droplets to increase the surface area for lipase action, so lipase acts faster.AQA
Surface area and reaction rate: The increased surface area allows lipase to act faster, so fat is broken down faster.AQA
Surface area of the membrane: The area available for particles to cross; a larger area lets more particles pass per unit time, increasing the rate.AQA
Surface area to volume ratio: As multicellular organisms increase in size, volume grows far faster than surface area, causing this ratio to decrease drastically.AQA, OCR
surgical access: Protective skeletal structures, including the cranium and vertebral column, alongside protective meninges, make physical surgical access difficult and…OCR
surrogate mother: The mother into which the embryo is later placed, where it develops into a clone of the adult donor.AQA
Surrogate motherhood: An adult female into whose womb the ball of cells is inserted so it can implant and continue its development; she is not the genetic parent.AQA
Survival and coordination: Reflexes free the brain to deal with complex tasks while automatic responses continue.AQA
Survival and reproduction: Successful competitors survive and reproduce, so their characteristics become more common.AQA
Susceptibility to disease: Being particularly prone to disease, which can occur in some breeds because reduced genetic variation makes a population less able to adapt to new diseases.AQA
Suspensory ligaments: These loosen when the ciliary muscles contract, and because they are loose the lens becomes thicker and more curved.AQA
Sustainability: Meeting present needs without damaging the ability of future generations to meet theirs.AQA
Sustainability trade-offs: High-protein feed can be costly and may compete with human food production, so its use involves trade-offs.AQA
Sustainable ecosystems: Recycling means ecosystems can continue to support life without a constant new supply of matter.AQA
Sustainable fisheries: Fishing kept at a level the stock can replace, so fish stocks are conserved at a sustainable level.AQA
Sustainable food production: Approaches include improving yields, reducing waste, using renewable resources and protecting soil and biodiversity.AQA
Sustainable level: Maintaining stocks by leaving enough breeding adults to produce the next generation.AQA
Sweat glands: These secrete sweat onto the skin surface, and as the sweat evaporates it takes latent heat from the skin, removing energy and cooling the body.AQA
sweating and shivering: Sweat glands secrete sweat, which cools the body as water evaporates, while rapid involuntary skeletal muscle contractions generate metabolic heat through…OCR
Symptom relief versus cure: Painkillers relieve symptoms such as pain or fever but do not kill pathogens, so they do not cure the infection.AQA
Symptom relief versus pathogen killing: Treating the effects of disease makes a patient more comfortable but does not remove the cause of the disease.AQA
synapse: The tiny gap at which a neurotransmitter is released, diffuses across and stimulates the next neurone, ensuring one-way transmission.AQA, OCR
synaptic transmission: Synapses are tiny gaps where a neurotransmitter diffuses across to pass the impulse to the next neurone, ensuring one-way transmission.AQA, OCR
Synthesis of biological molecules: Metabolic reactions that build larger molecules from smaller ones, such as joining glucose molecules into glycogen for storage.AQA
Synthesis reactions: Reactions that build larger molecules from smaller ones.AQA
systematic sampling: Along transect lines investigates changes in species abundance across environmental gradients.OCR
Systemic circuit: The circuit in which the left side pumps oxygenated blood around the body and back to the right side.AQA
systemic circulation: The circuit in which the muscular left ventricle pumps oxygenated blood under high pressure to systemic organs.OCR

T

tangent gradient: Calculating the gradient of a tangent drawn to a decay curve at different temperatures or moisture levels allows determination of instantaneous rate changes.OCR
tangents: A line drawn to the curve at time = 0, used to find the initial rate of reaction on continuous product-time graphs.OCR
tannins: Astringent chemicals produced by witch hazel that deter herbivores and inhibit pathogen growth.OCR
target cell receptors: Complementary protein receptors on the surface membranes or within the cytoplasm of target cells that bind matching hormone molecules.OCR
Target cells: Cells such as liver and muscle cells to which insulin travels in the blood plasma and which take up glucose from the blood.AQA
Target condition: The condition a drug is intended to treat, which the patients used in later trials have.AQA
Target organ: Hormones act only on target organs or cells that possess complementary receptors.AQA
Target organ specificity: A hormone only affects target organs or cells that have receptors complementary to that hormone, leaving other tissues unaffected.AQA
Target organs: The organs that hormones are carried in the blood to, where they produce specific effects.AQA
Target organs: kidney tubules: The kidney tubules are acted on by ADH, which makes them more permeable to water so more water is reabsorbed.AQA
targeted cancer drugs: Tumour genome sequencing identifies driver mutations, allowing targeted biological therapies that selectively destroy cancer cells with minimal collateral…OCR
targeted cancer therapy: Monoclonal antibodies carry radioactive isotopes or cytotoxic drugs directly to tumour surface antigens, destroying malignant cancer cells without harming…OCR
Targeted delivery: The antibody acts as a carrier, delivering an attached substance mainly to the cancer cells because it binds only to cells carrying that antigen.AQA
Targeted treatment: Antibodies can carry drugs or radioactive substances to specific cells such as cancer cells.AQA
Targeted treatment of disease: For cancer, the monoclonal antibody can be bound to a radioactive substance, a toxic drug or a chemical which stops cells growing and dividing.AQA
Technological progress in microscopy: Improvements in lens quality and magnification allowed scientists to see nuclei, mitochondria and other internal structures that early microscopes could not…AQA
Temperature: Affects the kinetic energy of particles, so a higher temperature makes them move faster and increases the rate of diffusion.AQA, OCR
Temperature and enzyme activity: Temperature affects enzyme activity and the survival of organisms, and a rise or fall outside a species' tolerance can force it to move or die out locally.AQA
Temperature control techniques: Using a water bath or electric heater to maintain a constant temperature during the investigation.AQA
Temperature receptors: Structures in the skin that detect changes in the external environment.AQA
temperature regulation in enzyme assays: Setting up and regulating water baths across a range of temperatures using thermostatically controlled heaters or Bunsen burners, and monitoring the…OCR
Template function of DNA strands: Base pairing allows accurate copying of DNA because each strand can act as a template.AQA
Tertiary consumer: The third consumer level in a food chain, counting the producer as level 1, containing consumers that eat other carnivores.AQA
Tertiary structure: The final shape of a protein is often described as its tertiary structure.AQA
Testes: The organ that produces testosterone, the main male reproductive hormone.AQA
Testing before medical use: A promising substance must be purified, tested for safety and effectiveness, and produced in a suitable form before it can be prescribed.AQA
testosterone: Produced by the testes, it stimulates sperm production and male secondary sexual characteristics.AQA, OCR
The completed human genome sequence: The complete base sequence of human DNA has been determined, giving a reference set of human DNA.AQA
The four DNA bases: DNA contains four bases: adenine, cytosine, guanine and thymine, represented by the letters A, C, G and T.AQA
The genetic code: The bases are the parts of the nucleotides that carry the genetic code, and their order along a DNA strand determines the sequence of amino acids in a protein.AQA
The genetic code as triplets: The base sequence is read in triplets, each triplet coding for one amino acid.AQA
The genome as the complete genetic material: The entire genetic material of an organism, including all genes and non-coding regions, not just the genes.AQA
The human genome as the complete genetic material of a cell: The complete set of genetic material in a human cell, including non-coding DNA as well as genes.AQA
The menstrual cycle: A cycle in which FSH causes an egg to mature, oestrogen thickens the uterus lining, LH triggers ovulation, and progesterone maintains the lining until it is…AQA
Theory of evolution: The idea, proposed by Charles Darwin, that living things change over long periods and that new species can form.AQA
Therapeutic cloning: A method of producing an embryo with the same genes as the patient, used as a source of stem cells for treatment.AQA
thermal energy: A substantial portion of the energy released during respiration is dissipated in this form.OCR
thermal equilibration of closed respirometers: Tubes are immersed and allowed to equilibrate for at least 5 to 10 minutes with three-way taps open before sealing, so internal air pressure and temperature…OCR
thermoregulation: The control of body temperature by the skin as a key effector organ, coordinated by the hypothalamus.OCR
Thermoregulation by the nervous system: The hypothalamus monitors blood temperature and triggers responses that either lower or raise body temperature, coordinated by the nervous system as negative…AQA
Thermoregulatory centre: A region of the brain that contains receptors sensitive to the temperature of the blood flowing through the brain and coordinates responses that restore core…AQA
thermoregulatory curves: Graphs depicting core body temperature fluctuations during thermoregulation, from which baseline and peak values can be extracted.OCR
thermostatically controlled electric water bath: An electrically heated water bath providing precise temperature control and avoiding open flames when heating reaction mixtures.OCR
thermostatically controlled water baths: Electric water baths maintain experimental tubes at constant temperatures between 10 and 50 °C.OCR
thirst mechanism: The hypothalamus stimulates thirst to encourage drinking when blood water potential falls, and suppresses it when excess water dilutes blood plasma.OCR
Thorns: Sharp structures that wound a feeding herbivore and so deter animals.AQA
Three-domain classification: A system developed by Carl Woese, using evidence from chemical analysis, that divides organisms into archaea, bacteria and eukaryota.AQA
Three-domain system: The system of Bacteria, Archaea and Eukaryota, which resulted from molecular evidence showing that archaea are distinct from bacteria.AQA
Thyroid gland: The gland in the neck that produces thyroxine, which is transported in the blood plasma to target cells around the body.AQA
thyroxine: A hormone secreted by the thyroid gland in the neck that travels in the blood and raises the basal metabolic rate.AQA, OCR
Timed observations: A series of results recorded at every 30-second interval rather than a single end point, so the time starch disappears can be identified.AQA
Timing of differentiation in animals and plants: Most types of animal cell differentiate at an early stage, whereas many types of plant cells retain the ability to differentiate throughout life.AQA
Tissue: A group of similar cells that work together to carry out a shared function, such as muscular tissue.AQA
Tissue culture: Small pieces of plant tissue are grown on a sterile nutrient medium containing auxins and other hormones, which promote cell division and shoot or root…AQA
tissue protection: Bypassing conscious cerebral processing reduces reaction time to prevent or minimise tissue damage.OCR
tissue rejection and immunosuppression: Donor cells display foreign antigens that provoke immune attack, so lifelong immunosuppressive drugs are needed unless therapeutic cloning uses patient nuclei.OCR
tissue repair: Adult stem cells divide to replace worn out cells and repair damaged tissues, such as blood cells.OCR
Tissues and organs: What the range of specialised cells produced by differentiation form in a multicellular organism.AQA
TMV: Tobacco mosaic virus gives mottled leaf discolouration, reducing chlorophyll so less light is absorbed, less photosynthesis occurs and growth is stunted.OCR
Tobacco mosaic virus: A viral disease that causes a mosaic pattern of discoloured patches on leaves, reducing photosynthesis and stunting growth.AQA
total magnification: Calculated by multiplying the eyepiece and objective lens powers.AQA
Toxic chemicals: Chemicals from factories that can poison water and soil if not stored or disposed of safely.AQA
Toxicity: The capacity of the drug to cause harm, tested at different concentrations to see whether it harms cells, tissues or whole organisms.AQA
Toxins: Substances secreted by bacteria that irritate the lining of the digestive system and affect the body's normal processes.AQA
Trace fossils: Footprints, burrows and rootlet traces can be filled or coated by sediment that later becomes rock, preserving traces rather than body parts.AQA
Trachea: The windpipe that carries air from the mouth and nose towards the lungs, and which divides into two bronchi.AQA
Traditional knowledge: Folk knowledge that often guided which plants and microorganisms were investigated.AQA
transcription: The DNA double helix unzips around a specific gene and one strand acts as a template to form a single-stranded mRNA molecule using complementary base rules.AQA, OCR
transfer efficiency: Calculated as the biomass transferred to the higher trophic level divided by the biomass at the lower trophic level, multiplied by one hundred percent.OCR
transgenic organisms: Organisms that have become genetically modified by receiving a gene from another organism.OCR
Translate information between graphical and numerical form: Moving data between a graph and numbers, such as plotting each pair of values as a point or reading values from axes, including interpolating between labelled…AQA
Translating between numerical and graphical form: Numerical data from a table can be translated into a graph by plotting time on the x-axis and the measured quantity on the y-axis.AQA
translation: The mRNA binds to a ribosome, where tRNA molecules carrying specific amino acids align complementary anticodons to mRNA codons, linking amino acids into a…AQA, OCR
Translocation: The movement of dissolved sugars and other substances through the phloem from sources, such as leaves, to sinks, such as growing regions and storage organs.AQA, OCR
Transmission: The passing on of the infection between humans by the mosquito, as malaria is not spread directly from person to person.AQA
Transmission and symptoms: Spread by inhaling droplets from an infected person's coughs or sneezes, or by direct contact with contaminated surfaces, then after an incubation period a…AQA
Transmission between hosts: The passing of an infectious disease from one organism to another.AQA
Transmission electron microscopy: A technique giving high-resolution 2D images of internal structure in thin specimens.AQA
Transmission routes: Direct contact, water or air, by which pathogens spread to a new host.AQA
Transpiration: The passive loss of water vapour from plant leaves via evaporation from mesophyll cell walls followed by diffusion through open stomata.AQA, OCR
Transpiration and plant water uptake: Transpiration from plants releases water vapour into the atmosphere, and some water on land is taken up by plant roots.AQA
transpiration and pulse graphs: Graphs of studies in which the independent variable is plotted on the horizontal x-axis and the dependent variable on the vertical y-axis.OCR
Transpiration pull: The pull created by the loss of water vapour that draws water up the xylem from the roots.AQA
transpiration rate: The rate at which water vapour diffuses out of the leaves, which alters the rate of root water uptake.OCR
transpiration stream: The upward movement of water and ions, driven largely by evaporation of water from leaf surfaces.AQA, OCR
Transport and gas exchange in animals: An efficient blood supply maintains a steep concentration gradient, and ventilation replaces air, keeping oxygen high and carbon dioxide low.AQA
Transport in the bloodstream: The blood carries the absorbed products to cells for use in respiration and growth.AQA
Transport of oxygen and glucose: A faster heartbeat circulates blood more quickly, so oxygen and glucose are delivered to the brain and muscles at a higher rate.AQA
Transport of substances by the circulatory system: Lactic acid diffuses into the bloodstream and plasma carries it through the circulatory system to the liver.AQA
Transport systems: Systems, such as the circulatory system in mammals or the xylem and phloem in plants, that move substances between exchange surfaces and all body cells.AQA
Treating bacterial disease: Antibiotics treat bacterial infections by killing bacteria or stopping their growth, so they work only when bacteria are the cause.AQA
Treating infertility with hormone therapy: Giving FSH and LH in a fertility drug, often as injections, so that eggs mature and ovulation occurs.AQA
Treating viral disease: Antibiotics do not treat viruses such as those causing colds or influenza, because viruses lack the bacterial targets antibiotics act on and reproduce inside…AQA
Treatment and control: Because the pathogen is a protist, antibacterial antibiotics are not effective, so control focuses on mosquitoes and protective drugs.AQA
Treatment and prevention: Antibiotics that target bacterial structures do not work against viruses, which explains why vaccination is so important.AQA
Treatment of diabetes: The extracted and purified insulin is used to treat diabetes, where patients cannot produce enough of their own insulin.AQA
Trend: The overall pattern in the data, such as increase, decrease, peak or plateau.AQA
trend interpretation: Analysing trends involves dividing the curve into a rising slope where x is limiting and a plateau where another factor limits.OCR
Trends and lines of best fit: Draw either a line of best fit or a smooth curve as appropriate, rather than joining points with jagged straight segments unless the question asks for it.AQA
triglycerides: Each triglyceride lipid molecule is synthesized by chemically bonding one molecule of glycerol to three fatty acid chains.OCR
triplet: Three consecutive bases along a DNA strand that together code for one amino acid.AQA
triplet code: The linear order of bases in DNA forms a genetic code read in triplets, where each triplet of three consecutive bases in a gene codes for one specific amino…OCR
trophic efficiency: Biomass transfer efficiency between trophic levels, expressed as both a fraction and a percentage, with a typical value of approximately 10%, corresponding to…OCR
Trophic level: Each level of the pyramid, identified from the data with its biomass value, with trophic level 1 at the bottom and higher levels above.AQA
Trophic level 1: The bottom bar of a pyramid of biomass, containing the producers.AQA
trophic level efficiency: Comparing the energy efficiency of crop production versus livestock rearing across trophic levels, where 90% of energy is lost between trophic levels.OCR
Trophic levels: Represented by numbers, starting at level 1 with plants and algae, so that feeding positions can be compared across different food chains.AQA, OCR
Trophic levels and food chains: Successive levels in a food chain, where less biomass and energy are available at each level because transfer between them is inefficient.AQA
Tropisms: Unequal auxin distribution causes unequal growth rates, which produce the bending seen in tropisms.AQA
Tumour: A mass of abnormal cells formed when control mechanisms fail and a cell divides repeatedly and uncontrollably.AQA
Turgid: The state of guard cells when they take in water by osmosis, becoming curved and opening the pore.AQA
Two-stage nuclear division: The cell divides twice: the first division separates homologous chromosomes, and the second separates the sister chromatids.AQA
two-stage process: Photosynthesis occurs in two main stages: a light-dependent stage and a light-independent stage.OCR
Type 1 diabetes: Characterised by uncontrolled high blood glucose levels, because the pancreas secretes insufficient insulin so glucose absorbed from the gut is not removed…AQA
Type 2 diabetes: The pancreas still produces insulin but body cells respond less well to it, and treatment often begins with diet and exercise to improve insulin sensitivity.AQA, OCR

U

ultrastructure: Sub-cellular structures revealed by electron microscopy, such as the double membranes and inner cristae of mitochondria, thylakoid grana in chloroplasts,…OCR
Uncontaminated culture: A culture that contains only the microorganism under investigation, with no unwanted bacteria or fungi.AQA
Uncontrolled cell division: The way the abnormal cells divide, although the resulting growth remains grouped together in one area.AQA
Unequal growth: A higher auxin concentration on one side makes those cells grow more than cells on the other side, and this unequal growth bends the organ.AQA
Unfertilised egg cell: A cell taken from a female of the same species, whose nucleus is removed before the adult body-cell nucleus is inserted.AQA
Unicellular: Organisms, such as bacteria and amoeba, that consist of one cell which performs every life process.AQA
unit conversion: Changing a measurement between units such as metres, millimetres, micrometres and nanometres, for example 1 mm = 1000 µm and 1 µm = 1000 nm.AQA
unit conversions in microscopy: Convert millimetres to micrometres by multiplying by 1000, and micrometres to nanometres by multiplying by 1000.OCR
Units: Stated consistently, such as cm³ s⁻¹ or g min⁻¹, when calculating rate.AQA
units of measurement: The standard International System units used in microscopy are millimetres (mm), micrometres (µm), and nanometres (nm).OCR
units of rate: Compound units written using standard indices such as cm³ s⁻¹ or words like cm³ per second.OCR
universal process: A chemical process occurring continuously in all living cells across all kingdoms of life.OCR
Unsustainable: Describes a situation where the ocean cannot replace the fish as quickly as they are removed.AQA
Urea: Ammonia is converted into urea in the liver, which is less harmful and is carried in the blood to the kidneys.AQA
urine volume and concentration: During dehydration or heavy sweating a small volume of concentrated urine is excreted to conserve water, while high fluid intake produces a large volume of…OCR
Use of monoclonal antibodies in medicine: In cancer treatment the antibody is chosen because its antigen is found on the surface of cancer cells, and a cell-killing or radioactive substance is…AQA
Use of the microscope: Bacteria require higher magnification to observe internal structures compared to eukaryotic cells.AQA
Use of water baths in practical work: A water bath or electric heater maintains a steady temperature, such as 37 °C, which is close to human body temperature.AQA
Using data: Reading the information given, such as a table of features or a list of organisms, and matching the features to the ranks.AQA
Using evidence from data: Reasoning from the supplied data or habitat description rather than recalling a list, quoting or referring to the data when suggesting competition factors.AQA
uterine endometrium: Repaired and thickened by oestrogen, then maintained by progesterone in preparation for a fertilised embryo.OCR
Uterus (womb): The site into which one or two embryos are inserted at the tiny ball of cells stage.AQA

V

Vaccination: Introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies.AQA
Vaccination and antivirals: Some viral infections are prevented by vaccination and some are treated with antiviral medicines, while many are managed by rest and symptom relief.AQA
vaccination and herd immunity: Introducing dead, attenuated, or fragment pathogens containing specific antigens stimulates lymphocytes to produce complementary antibodies and memory cells,…OCR
Vaccination and immunity: Giving immunity so that individuals do not become hosts who pass pathogens on.AQA
Vaccination and prevention: Most young children are vaccinated, usually as part of the MMR vaccine, which protects the individual and helps prevent outbreaks through herd immunity.AQA
Valid comparison: A comparison of disinfectants or antibiotics in which all plates start with the same pure culture and are treated identically apart from the variable being…AQA
Valve replacement: Faulty valves can be treated by replacing the valve with a mechanical or biological valve.AQA
Variables and axes: The independent variable goes on the x-axis, such as concentration of sugar solution in mol/dm³, and the dependent variable goes on the y-axis, such as…AQA
Variation: Differences in the characteristics of individuals in a population, which may be due to genetic causes, environmental causes, or a combination of genes and the…AQA
Variation and mutation: Individuals in a population differ because of mutations and sexual reproduction.AQA
Variation within populations: Individuals in a population vary because of differences in their genes, and some variants give a better fit to the local conditions.AQA
Variation within species: Individual organisms within a particular species show a wide range of variation for a characteristic, arising from differences in genes and from environmental…AQA
vasoconstriction: Arterioles constrict, reducing superficial blood flow to minimise radiative heat loss and redirecting blood to deep tissues to conserve heat.AQA, OCR
Vasodilation: The smooth muscle in the walls of arterioles supplying the skin capillaries relaxes, so the arterioles widen and more blood flows through the skin capillaries.AQA, OCR
Vector: The mosquito, which takes up the malarial protist when it feeds on an infected person and transmits it between humans.AQA
Vector control: Destroying or controlling vectors, for example using mosquito nets and insecticides, so that pathogens are stopped from reaching new hosts.AQA
Vectors: Biological carriers such as mosquitoes that spread pathogens, distinct from the microscopic pathogen causing the disease.AQA, OCR
Vectors and transmission: Mosquitoes are the vectors that transmit the malaria protist between humans, and control measures aim to break this transmission cycle.AQA
veins: Blood vessels that carry blood back to the heart and have relatively thin walls and valves that prevent the backflow of blood.AQA, OCR
Ventilation: The process that increases during exercise to take in more oxygen and remove the extra carbon dioxide produced by respiring muscles.AQA
vessel arrangement: The order of vessels from heart to arteries to arterioles to capillaries to venules to veins to heart.OCR
Viral disease: Measles is a viral disease showing symptoms of fever and a red skin rash.AQA
Viral infection: A virus hijacks the plant's cells to make more virus particles, and the mosaic pattern is a symptom of it.AQA
Viral infection and immune response: When a person first becomes infected with HIV, the virus multiplies in the body and the immune system responds.AQA
Viral replication inside host cells: Viruses reproduce inside host cells, using the host's own machinery and structures to copy themselves.AQA
Viral structure and reproduction: Viruses are not cells but tiny particles that have no cell wall, no bacterial ribosomes and no other bacterial structures, and they reproduce only inside host…AQA
Viral versus bacterial infections: Antibiotics kill bacteria, not viruses, so they are ineffective against viral infections such as colds or flu.AQA
Viruses: Non-cellular agents that reproduce inside host cells and destroy them.AQA
Viruses and uncontrolled cell division: Viruses living in cells can be the trigger for cancers by disrupting normal control of cell division, so cells divide uncontrollably and a tumour forms.AQA
visual identification: Identification of symptoms such as leaf spots, mosaic patterns, or skin rashes.OCR
Vitamin A deficiency: A lack of vitamin A that causes blindness, which matters where diets are based mainly on plain rice.AQA
volumetric gas measurement: Oxygen gas volume is measured using a calibrated capillary tube or gas syringe readable to 0.05 cm³, or bubble length with a millimetre ruler.OCR
volumetric photosynthometer measurement: Collecting oxygen gas in a microburette or capillary photosynthometer and measuring bubble length or volume to improve measurement accuracy.OCR
Vulnerability: Being more likely to be affected severely, as in countries that depend on rain-fed agriculture or lack money to import food.AQA

W

Warning colouration: Bright, conspicuous patterns on prey animals that predators learn to avoid because the prey is toxic or dangerous.AQA
Waste management: Handling waste and chemical materials carefully, including treating sewage, storing chemicals safely, recycling, using filters and disposing of waste in…AQA
Waste production and management: More resource use leads to more waste, including packaging, food waste, sewage and waste gases, and managing this increasing waste is a challenge.AQA
Water and gas availability: Availability of water affects photosynthesis, transport and survival, while the composition of atmospheric gases affects photosynthesis and respiration and…AQA
Water and ion balance: If you are dehydrated, less water is lost in urine; if you drink a lot, more dilute urine is produced.AQA
Water and salt balance: Mechanisms that balance water and salt across membranes, an adaptation to very high salt concentration.AQA
water balance: Maintained by the kidneys varying the amount and concentration of urine and hence water excreted, conserving or excreting water obtained from diet and…OCR
Water balance in body fluids: Keeping the water content of cells and body fluids within a narrow range, because efficient cell function depends on it.AQA
water bath: A controlled, flameless heat source for incubating cultures or melting cooled agar at a set temperature, avoiding overheating or igniting flammable materials.OCR
Water concentration gradients: Net movement of water is from the side with a higher water concentration (dilute solution) to the side with a lower water concentration (concentrated solution).AQA
water cycle: Circulates fresh water essential for terrestrial survival, as solar energy drives evaporation and transpiration, water vapour condenses into clouds and…OCR
Water cycle processes: Water evaporates from oceans and transpires from leaves, condenses into clouds, falls as rain, then runs through soil and rivers back to the sea.AQA
Water movement in plants: Water moves upwards in the transpiration stream from roots to leaves.AQA
Water pollution: Pollution that can occur in water, from sewage, fertiliser or toxic chemicals.AQA
water potential gradient: The gradient that is steepened when higher temperature lowers surrounding relative humidity, driving faster transpiration.OCR
Water reabsorption by osmosis: More water is reabsorbed by osmosis into the blood when the tubules are more permeable, producing a smaller volume of more concentrated urine.AQA
Water uptake by osmosis: Water moves across the partially permeable membrane from a dilute solution in the soil to a more concentrated solution inside the cell.AQA
water uptake measurement: An air bubble is introduced into the capillary tube; as the shoot transpires, water uptake pulls the bubble along a scale.OCR
water uptake potometry: Measuring uptake of water using an aquatic potometer, recording meniscus movement per minute as a rate of photosynthesis.OCR
Waxy cuticle: An impermeable, hydrophobic lipid layer covering the upper and lower epidermal surfaces, preventing water accumulation where fungal spores could germinate and…AQA, OCR
Waxy cuticle on leaves: A tough covering on the leaf surface that repels water, so pathogens cannot easily settle and enter.AQA
White blood cell function: White blood cells engulf pathogens and produce antibodies or antitoxins that destroy pathogens or neutralise their toxins.AQA
White blood cells: These defend the body: phagocytes engulf and digest pathogens, and lymphocytes produce antibodies and antitoxins.AQA
Widespread famine: A severe shortage of food that can occur in some countries if rains fail, especially where people cannot grow or buy enough food.AQA
Word equation: Glucose → ethanol + carbon dioxide, representing anaerobic respiration in plant and yeast cells.AQA
Working scientifically: Skills developed through the practical activity, covering AT 1, 3 and 4, in which students plan the method, record clear results and interpret the evidence…AQA
Working scientifically skills: Key apparatus and techniques covering accurate measurement, observation and measurement of biological processes in the field, safe and ethical use of living…AQA
Worldwide fieldwork and specimen collection: Travelling extensively across regions such as South America and the Malay Archipelago, collecting thousands of specimens and recording where each was found.AQA

X

Xylem: Tissue made of dead, hollow cells strengthened with lignin, allowing water and mineral ions to move upward and providing support.AQA
xylem adaptations: Dead, hollow, elongated cells aligned end-to-end with absent end walls, forming an uninterrupted capillary lumen for rapid mass flow of water and mineral ions.OCR

Z

zone of inhibition: A clear area where bacteria do not grow, left where an effective antiseptic or antibiotic diffuses into the agar.AQA
zone of inhibition measurement: The diameter of each clear circular zone is measured in two perpendicular directions using a millimetre ruler to calculate mean diameter and clear zone area.OCR
zones of inhibition: Clear circular areas that form where bacterial growth is prevented on inoculated agar lawns.OCR
Zygote: The single fertilised cell produced when fertilisation occurs outside the body, which divides by mitosis to form an embryo.AQA
Zygote and embryo development: Each sperm cell fuses with an egg cell, combining their genetic material to form a zygote, which divides by mitosis to form an embryo.AQA
Zygote formation: The production of a cell with two sets of chromosomes when a sperm cell fuses with an egg cell.AQA

Where these terms come from

Each definition is one we publish on a Biology GCSE topic page or study guide. Open a term to see how each exam board words it and which topic it belongs to. For the full course, go to Biology revision or the glossary for every subject.

Revise Biology with these terms

Create a free account to practise exam questions and get feedback on your answers.

Start free

A week of Premium from your first lesson · Then the free plan continues · No card, no charge

Biology topics

A

B

C

D

E

F

G

H

I

J

K

L

M

N

O

P

Q

R

S

T

U

V

W

X

Z

Where these terms come from

Revise Biology with these terms

Cookies on MasteryMind