Nutrient cycles — Cambridge IGCSE Combined Science
How carbon is cycled between the air, living things and fossil fuels by photosynthesis, feeding, respiration, decomposition and combustion.
Revision notes
1 short note, in the order of the specification. Each one in short:
The carbon cycle moves carbon between the air, living organisms, dead material and fossil fuels. Photosynthesis removes carbon dioxide from the air, and feeding passes carbon compounds along food chains. Respiration by plants, animals and decomposers returns carbon dioxide, as does combustion of fossil fuels and wood. Some buried dead organisms form coal, oil and natural gas.
Exam questions
3 exam-style questions (8 marks), each with its mark scheme.
Answer the questionsFlashcards
4 cards: flip them, mark what you knew, and practise the rest.
Practise the cardsMind map
The whole of organisms and their environment on one page, so you can see where this subtopic fits.
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Free PDFs to print or save.
Quick check questions
Which process removes carbon dioxide from the air?
Show answer
Photosynthesis.
Name three processes that add carbon dioxide to the air.
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Respiration, decomposition and combustion.
How are fossil fuels formed?
Show answer
From dead organisms that were buried and did not decompose fully, over millions of years.
Written and checked against the Cambridge IGCSE Combined Science (0653) specification · Updated October 2026