Abiotic factors — AQA GCSE Biology
Test yourself on Abiotic factors with AQA GCSE practice questions.
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Abiotic factors explained
A community is all the populations of different species living together in a habitat.
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Abiotic factors are the non-living conditions of that habitat, such as light intensity, temperature, moisture, soil pH and mineral content, wind, carbon dioxide for plants and oxygen for aquatic animals. To explain an effect, identify the factor that has changed, state the direction of change, then trace the consequence through the organisms. For example, if light intensity falling in a wood reduces photosynthesis in ground plants, their growth slows, so herbivores have less food and their numbers may fall, which can also reduce predator numbers. Always link the changed factor to a named process such as photosynthesis, enzyme activity, transpiration or gas exchange, then to survival, reproduction and population size.
Abiotic (non-living) factors which can affect a community are: • light intensity • temperature • moisture levels • soil pH and mineral content • wind intensity and direction • carbon dioxide levels for plants • oxygen levels for aquatic animals.
Abiotic factors are the non-living physical and chemical conditions of a habitat, and each can limit the distribution and abundance of organisms in a community. Light intensity supplies the energy for photosynthesis, so it affects plant growth and the food available to consumers. Temperature controls the rate of enzyme-controlled reactions, so extremes reduce metabolism and survival. Moisture levels affect transpiration, transport and the availability of water for reactions. Soil pH and mineral content affect nutrient availability and root function, so they influence plant growth. Wind intensity and direction increase transpiration and heat loss and can disperse seeds, spores and pollutants. Carbon dioxide is a raw material for photosynthesis in plants, while oxygen is needed for aerobic respiration by aquatic animals.
Students should be able to extract and interpret information from charts, graphs and tables relating to the effect of abiotic factors on organisms within a community.
Charts, graphs and tables present ecological data such as the number of organisms at different light intensities, temperatures or oxygen concentrations. To extract information, read the axes, units, labels and keys carefully, then locate the value or category you need. To interpret, describe the overall trend, quote figures with units, and explain the trend using biology. For example, a graph showing plant height rising as light intensity increases up to a plateau can be explained by photosynthesis increasing until another factor becomes limiting. A table of aquatic invertebrate numbers against oxygen concentration can show that most species peak at higher oxygen levels, which links to aerobic respiration. Always connect the pattern in the data to a named abiotic factor and its effect on the organisms.
Your focus
- Identify the abiotic factor that has changed and state the direction of change
- Link the changed factor to a named biological process and to the survival or reproduction of organisms
- Construct a logical chain of consequences through the community using the data or context provided
Show all 9 objectives
- List the seven abiotic factors that can affect a community
- Distinguish abiotic from biotic factors using the non-living criterion
- Link each named abiotic factor to at least one biological process or effect on organisms
- Read values accurately from charts, graphs and tables, including axes, units and keys
- Describe trends and compare data for organisms under different abiotic conditions
- Explain trends by linking the abiotic factor to a named biological process
Abiotic factors exam tips
Marking Points
- Identifies the specific abiotic factor that has changed and states whether it has increased or decreased
- Links the changed factor to a named biological process, such as photosynthesis, enzyme activity, transpiration or gas exchange
- Explains the consequence for survival or reproduction of organisms in the community
- Traces the effect through more than one trophic level or species where the data or context allows
- Uses the data or context provided, quoting values or trends, rather than giving a generic answer
- Uses correct ecological terminology, including community, population, habitat and abiotic
- States that abiotic factors are non-living conditions of a habitat
- Names light intensity and links it to photosynthesis and plant growth
- Names temperature and links it to enzyme activity and metabolic rate
- Names moisture levels and links them to transpiration, transport or water availability
- Names soil pH and mineral content and links them to nutrient availability or plant growth
- Names wind intensity and direction and links them to transpiration, heat loss or dispersal
- Names carbon dioxide for plants and oxygen for aquatic animals and links each to photosynthesis or aerobic respiration respectively
- Reads axes, units, labels and keys correctly before quoting any value
- Describes the overall trend, such as increase, decrease, peak or plateau
- Quotes specific values or ranges from the chart, graph or table with correct units
- Compares data for different species, sites or conditions where the resource allows
- Explains the trend by linking the abiotic factor to a named biological process
- Recognises anomalies or limitations in the data and avoids overgeneralising from a single point
Examiner Tips
- 💡Underline the factor and the direction of change in the question before you start writing.
- 💡Use the connectives because, so and therefore to build a logical chain from factor to population.
- 💡If data are given, quote at least one value or trend and explain what it shows about the community.
- 💡Learn the list as seven named factors and be ready to give one effect for each.
- 💡When asked to name a factor, add a brief consequence to show understanding and secure the explanation mark.
- 💡Use the phrase non-living when defining abiotic to distinguish it clearly from biotic.
- 💡Quote figures with units and say what they show, rather than leaving numbers unexplained.
- 💡Use the pattern words increase, decrease, plateau and optimum to describe trends precisely.
- 💡When explaining, name the abiotic factor and the process, such as photosynthesis or respiration, in the same sentence.
Common Mistakes
- Describing the factor without explaining a consequence; the correction is to state the effect on a named process and then on the organism.
- Treating a biotic factor, such as predation, as abiotic; the correction is to check whether the factor is living or non-living before answering.
- Giving a one-step answer that stops at the plant; the correction is to continue the chain to consumers and, where relevant, decomposers.
- Classifying a living factor such as food supply or disease as abiotic; the correction is to check that the factor is non-living.
- Confusing the roles of carbon dioxide and oxygen; the correction is to link carbon dioxide to photosynthesis in plants and oxygen to aerobic respiration in aquatic animals.
- Treating soil pH as a direct nutrient; the correction is to state that pH affects the availability of minerals to plants.
- Reading the wrong axis or ignoring the units; the correction is to check both axes and the key before quoting a value.
- Describing each point separately instead of stating the overall trend; the correction is to summarise the pattern first, then support it with figures.
- Giving a biological explanation that does not name the abiotic factor; the correction is to state the factor and the process it affects.