AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Students should: • recall that many different materials cycle through the…
Full specification wording
How materials are cycled: Students should: • recall that many different materials cycle through the abiotic and biotic components of an ecosystem • explain the importance of the carbon and water cycles to living organisms.
Materials such as carbon and water move repeatedly between the non-living (abiotic) parts of an ecosystem — air, water, soil and rocks — and the living (biotic) parts — plants, animals and…
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 1 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Materials such as carbon and water move repeatedly between the non-living (abiotic) parts of an ecosystem — air, water, soil and rocks — and the living (biotic) parts — plants, animals and decomposers. Carbon enters plants as carbon dioxide during photosynthesis and returns to the air when organisms respire, when decomposers break down dead matter, and when fuels burn. Water evaporates from oceans and transpires from leaves, condenses into clouds, falls as rain, then runs through soil and rivers back to the sea. These cycles matter because they keep carbon and water available: carbon forms carbohydrates, proteins and fats, while water is the solvent in which cell reactions happen and a reactant in photosynthesis. Without recycling, nutrients would be locked in dead matter and life could not continue.
What earns the marks
- Carbon is taken from the air as carbon dioxide by producers during photosynthesis and built into glucose and other biological molecules.
- Carbon returns to the atmosphere through respiration by producers, consumers and decomposers, and through combustion of fossil fuels and other organic material.
- Decomposers such as bacteria and fungi break down dead organisms and waste, releasing carbon compounds and mineral ions back into the soil and air.
- Water moves by evaporation from oceans and lakes, transpiration from plant leaves, condensation to form clouds, precipitation as rain or snow, and runoff or percolation back to water bodies.
- Carbon compounds are needed for growth and energy release, while water is needed as a solvent, a transport medium and a reactant in photosynthesis.
- Cycling keeps the supply of carbon and water available to organisms rather than allowing them to be lost permanently in one store.
Common mistakes and how to put them right
Thinking carbon is destroyed when organisms respire.
Put it right by stating that carbon atoms are rearranged and released as carbon dioxide, not destroyed.
Confusing transpiration with respiration.
Put it right by describing transpiration as loss of water vapour from leaves and respiration as release of energy from glucose.
Describing the water cycle as only rainfall.
Put it right by including evaporation, transpiration, condensation, precipitation and runoff or percolation.
Exam tips
- Use the words abiotic and biotic correctly: abiotic means non-living components such as air, water and soil, while biotic means living components such as plants, animals and decomposers.
- When explaining importance, link each cycle to a named process or need, for example carbon for building proteins and water as the solvent for cell reactions.
- Practise drawing a simple labelled cycle diagram with arrows showing direction of movement, then describe each arrow in a sentence.
Try the lesson
The start of the How materials are cycled: Students should: • recall that many different materials cycle through the abiotic and biotic components of an ecosystem • explain the importance of the carbon and water cycles to living organisms. lesson, made from checked teaching notes for this specification point.
Have a go first
Which process removes carbon dioxide from the air and passes its carbon into living organisms?
Listen
Materials such as carbon and water move repeatedly between the non-living (abiotic) parts of an ecosystem — air, water, soil and rocks — and the living (biotic) parts — plants, animals and decomposers. Carbon enters plants as carbon dioxide during photosynthesis and returns to the air when organisms respire, when decomposers break down dead matter, and when fuels burn. Water evaporates from oceans and transpires from leaves, condenses into clouds, falls as rain, then runs through soil and rivers back to the sea. These cycles matter because they keep carbon and water available: carbon forms carbohydrates, proteins and fats, while water is the solvent in which cell reactions happen and a reactant in photosynthesis. Without recycling, nutrients would be locked in dead matter and life could not continue. A strong answer earns marks for these points. Carbon is taken from the air as carbon dioxide by producers during photosynthesis and built into glucose and other biological molecules. Carbon returns to the atmosphere through respiration by producers, consumers and decomposers, and through combustion of fossil fuels and other organic material. Decomposers such as bacteria and fungi break down dead organisms and waste, releasing carbon compounds and mineral ions back into the soil and air. Water moves by evaporation from oceans and lakes, transpiration from plant leaves, condensation to form clouds, precipitation as rain or snow, and runoff or percolation back to water bodies. A common slip: Thinking carbon is destroyed when organisms respire. Instead, stating that carbon atoms are rearranged and released as carbon dioxide, not destroyed. Exam tip: Use the words abiotic and biotic correctly: abiotic means non-living components such as air, water and soil, while biotic means living components such as plants, animals and decomposers.
Key words
Say what each word means before you turn the card.
Abiotic components
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Biotic components
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Carbon cycle processes
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Water cycle processes
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See every definition
- Abiotic components
- The non-living parts of an ecosystem, such as air, water, soil and rocks, through which materials cycle.
- Biotic components
- The living parts of an ecosystem, such as plants, animals and decomposers, through which materials cycle.
- 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 fuels burn.
- 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.
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