# Explain how carbon in the bodies of dead organisms is returned to the atmosphere.

> AQA A-Level Biology (7402) — 3.5.4 Nutrient Cycles · Explain · 5 marks

## Mark scheme (5 marks)

1. Decomposers (bacteria / fungi) break down the dead organisms
2. Decomposers carry out respiration
3. Respiration releases carbon dioxide
4. The carbon in the organic molecules of the dead organism is converted to carbon dioxide
5. Carbon dioxide returns to the atmosphere where it can be used by plants for photosynthesis

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