# Explain how the carbon stored in a dead tree is returned to the atmosphere.

> WJEC GCSE Biology (Wales) — 1.6.2 Nutrient cycles · Explain · 4 marks

## Mark scheme (4 marks)

1. Decomposers / bacteria / fungi break down the dead tree (decomposition / decay)
2. Decomposers respire, releasing carbon dioxide into the atmosphere
3. Carbon is also stored in fossil fuels if dead material is compressed / buried over millions of years (reference to incomplete decomposition leading to fossil fuel formation)
4. Burning / combustion of wood (or fossil fuels formed from organic matter) releases carbon dioxide into the atmosphere

## Related

- [Revision notes for WJEC GCSE Biology (Wales)](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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