# Explain how nitrogen from the atmosphere becomes available to a plant as nitrates in the soil.

> Pearson Edexcel International GCSE Biology (4BI1) — 4.3 Cycles within ecosystems · Explain · 4 marks

## Mark scheme (4 marks)

1. Nitrogen-fixing bacteria convert atmospheric nitrogen gas into nitrates (or nitrogen-containing compounds)
2. Nitrogen-fixing bacteria may live in the soil or in the root nodules of plants
3. Nitrifying bacteria convert ammonia (in the soil) into nitrates
4. Nitrates are absorbed by (the roots of) the plant

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Biology (4BI1)](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-nitrogen-from-the-atmosphere-698b0429) · Published by Druglandscape Ltd.