# Biodiversity is important for the stability of ecosystems. Explain why a reduction in biodiversity can threaten the survival of species within an ecosystem, and describe one way in which human activities can reduce biodiversity.

> Pearson Edexcel A-Level Biology A (9BI0) — Topic 3 Classification and Biodiversity · Explain · 5 marks

> Scientists monitoring a tropical rainforest recorded a sharp decline in the number of different plant species over a ten-year period. During the same period, several animal species that depended on those plants also disappeared from the area.

## Mark scheme (5 marks)

1. Biodiversity refers to the variety of different species (or organisms) in an ecosystem / habitat
2. Species within an ecosystem are interdependent, so if one species declines / disappears, others that depend on it are also affected
3. A reduction in biodiversity reduces the stability of an ecosystem because there are fewer alternative food sources / relationships, making it more vulnerable to change
4. Correct identification of a human activity that reduces biodiversity — e.g. deforestation / habitat destruction / pollution / over-hunting / introduction of non-native species / monoculture farming
5. Explanation of how that human activity reduces biodiversity — linked clearly to the named activity

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](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/biodiversity-is-important-for-the-stability-52eefa00) · Published by Druglandscape Ltd.