# Describe how the carbon cycle returns carbon dioxide to the atmosphere, referring to the roles of living organisms and combustion.

> OCR GCSE Biology A: Gateway Science (J247) — B4.1 Ecosystems · Describe · 4 marks

> Peat bogs store vast amounts of carbon in partially decomposed plant material. In some countries, peat is drained and burnt as a fuel, while in others it is left undisturbed. Scientists are concerned about the impact of disturbing peat bogs on atmospheric carbon dioxide levels.

## Mark scheme (4 marks)

1. Respiration by living organisms releases carbon dioxide into the atmosphere
2. Decomposers / microorganisms break down dead organic matter, releasing carbon dioxide
3. Combustion of organic matter / fossil fuels / peat releases carbon dioxide
4. Photosynthesis removes carbon dioxide from the atmosphere (by producers / plants)

## Key terms

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

## Related

- [Revision notes for OCR GCSE Biology A: Gateway Science (J247)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" 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/describe-how-the-carbon-cycle-returns-729fd0bf) · Published by Druglandscape Ltd.