# Explain how the carbon cycle returns carbon dioxide to the atmosphere after a plant dies and is broken down.

> Edexcel GCSE Biology (1BI0) — 9.1 Ecosystems · Explain · 4 marks

> When plants die, their bodies contain carbon compounds built up during photosynthesis. These carbon compounds must be broken down before the carbon can re-enter the atmosphere.

## Mark scheme (4 marks)

1. Decomposers break down the dead plant material / dead organic matter
2. Decomposers release enzymes that catalyse the breakdown of complex organic molecules into simpler organic matter / compounds
3. The decomposers (and other organisms that feed on the dead material) respire the carbon compounds
4. Respiration releases carbon dioxide back into the atmosphere

## Key terms

- [carbon cycle](https://www.gradenine.co.uk/glossary/carbon-cycle)

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-carbon-cycle-returns-1aa72e74) · Published by Druglandscape Ltd.