The carbon cycle Cambridge IGCSE Biology (9–1) revision
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In plain words
Nature doesn't have a rubbish bin. The carbon in your body has been in the air, in plants and in other animals before you, and will be again. The same atoms go round and round, and living things keep them moving.
Three things to know
- Photosynthesis takes carbon dioxide out of the air and builds it into plants. Feeding passes the carbon on to animals.
- Respiration (by plants, animals and decomposers) returns carbon dioxide to the air. So does combustion: burning wood or fossil fuels.
- When organisms die, decomposers break them down and release the carbon as carbon dioxide. Where they don't decay, over millions of years they can become fossil fuels.
Tips and tricks
- One process takes carbon dioxide out of the air (photosynthesis). Three put it back (respiration, decomposition, combustion).
- Decomposers release carbon dioxide by respiring. "Decay" on its own isn't the full answer.
It lands in your notebook with its questions as flashcards.
The carbon cycle: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
Which process removes carbon dioxide from the air?
Plants use it to make glucose.
Which process returns carbon dioxide to the air?
All living things respire.
How does carbon pass from a plant to an animal?
The animal eats carbon compounds made by the plant.
What do decomposers do in the carbon cycle?
They respire as they feed on dead material.
Which activity adds the most extra carbon dioxide to the atmosphere?
It releases carbon stored underground for millions of years.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 7 marks. Write your answers on paper, then check them.
The carbon cycle
Cambridge IGCSE Biology (9–1) 0970 · 7 marks · papermunch.org
Name ______________________________ Date ______________
Name three processes that release carbon dioxide into the atmosphere.[3]
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Respiration, decomposition (respiration by decomposers) and combustion.
Describe how the carbon in carbon dioxide in the air becomes part of a rabbit.[2]
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A plant takes in the carbon dioxide and uses it in photosynthesis to make glucose (and other carbon compounds). The rabbit eats the plant.
Explain why burning fossil fuels increases the amount of carbon dioxide in the atmosphere.[2]
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Fossil fuels contain carbon that has been locked away for millions of years. Burning them releases it as carbon dioxide faster than photosynthesis can remove it.
Answers: The carbon cycle
- 1. Respiration, decomposition (respiration by decomposers) and combustion.
- 2. A plant takes in the carbon dioxide and uses it in photosynthesis to make glucose (and other carbon compounds). The rabbit eats the plant.
- 3. Fossil fuels contain carbon that has been locked away for millions of years. Burning them releases it as carbon dioxide faster than photosynthesis can remove it.