IGCSE Biology glossary
Carbon cycle
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
The biogeochemical cycle in which carbon is recycled between the atmosphere, living organisms, the ocean and the Earth's crust. Carbon dioxide is removed from the atmosphere by photosynthesis and returned by respiration, combustion and decomposition.
What to include in an exam answer
Know the four main processes: photosynthesis (removes CO2), respiration (returns CO2), combustion (returns CO2 from fossil fuels), decomposition (returns CO2 from dead organisms). Be able to label a carbon cycle diagram.
Example in context
Describe two ways in which carbon dioxide is returned to the atmosphere (2 marks): Carbon dioxide is released by respiration of living organisms and by combustion of fossil fuels.
Related syllabus topic
Organisms & their environment