Flashcards · Biology · Cycles in Ecosystems
The Carbon Cycle
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Which process takes carbon dioxide out of the air?
Photosynthesis.
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How does carbon pass along a food chain?
By feeding, when one organism eats another.
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Which processes return carbon dioxide to the air?
Respiration, decay and combustion.
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Which living things respire?
Plants, animals and decomposers.
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Why does decay release carbon dioxide?
The decomposers respire.
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What is combustion?
Burning.
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What gas is released when fossil fuels are burnt?
Carbon dioxide.
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How are fossil fuels formed?
From the remains of dead plants and animals over millions of years.
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What percentage of the air is carbon dioxide?
About 0.04 per cent.
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Where is carbon stored for a long time in living things?
In the wood of trees.
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Why is carbon important to living things?
It is part of carbohydrates, proteins and fats.
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What makes the carbon dioxide level in the air stay roughly constant?
Photosynthesis removing it and respiration, decay and combustion adding it.
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What happens to the level of carbon dioxide if fossil fuels are burnt faster than it is removed?
It rises.
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In which form is carbon in the air?
Carbon dioxide.
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Which organisms put carbon back into the air when an animal dies?
Decomposers.
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Name the process marked X and say what happens. Death and decay. Decomposers break down dead plants and waste, and they release carbon dioxide into the air by respiration.
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Describe the carbon cycle. 
Photosynthesis takes carbon dioxide into plants. Feeding passes carbon to animals. Respiration by plants, animals and decomposers returns carbon dioxide to the air. Death and decay return carbon dioxide by the respiration of decomposers. Combustion of fossil fuels also releases carbon dioxide.