# Explain how carbon stored in fossil fuels is returned to the atmosphere and why this contributes to an increase in atmospheric carbon dioxide levels.

> Cambridge International IGCSE Biology (0610) — 19.3 Nutrient cycles · Explain · 4 marks

## Mark scheme (4 marks)

1. Fossil fuels are burned / combustion of fossil fuels occurs
2. Combustion releases carbon dioxide into the atmosphere
3. Deforestation reduces the number of trees / plants available to remove carbon dioxide by photosynthesis
4. Carbon dioxide cannot be removed / broken down as quickly as it is being released, so levels increase

## Key terms

- [fossil fuel](https://www.gradenine.co.uk/glossary/fossil-fuel)

## Related

- [Revision notes for Cambridge International IGCSE Biology (0610)](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-carbon-stored-in-fossil-7eb64310) · Published by Druglandscape Ltd.