# Explain how the combustion of fossil fuels and the process of photosynthesis affect the concentration of carbon dioxide in the atmosphere.

> Edexcel GCSE Biology (1BI0) — 9.3 Material cycles · Explain · 4 marks

> Carbon dioxide is continuously entering and leaving the atmosphere through a range of processes. Human activities have significantly altered the balance of carbon dioxide in the atmosphere over recent centuries.

## Mark scheme (4 marks)

1. Combustion of fossil fuels releases carbon dioxide into the atmosphere, increasing its concentration
2. This occurs because the carbon stored in fossil fuels is oxidised and released as carbon dioxide gas
3. Photosynthesis removes/absorbs carbon dioxide from the atmosphere, decreasing its concentration
4. During photosynthesis, carbon dioxide is converted into organic molecules/glucose/biomass, incorporating carbon into living organisms

## Key terms

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

## 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-combustion-of-fossil-9ede6c82) · Published by Druglandscape Ltd.