# A species of Arctic fox lives in a tundra ecosystem. The foxes have white fur and feed on lemmings. Over many generations, climate change causes the tundra to become warmer and the snow cover to decrease, exposing more bare brown ground for longer periods each year. Explain how natural selection could lead to a new variety of Arctic fox with brown fur becoming more common in this population over many generations.

> OCR A-Level Biology B — Advancing Biology (H422) — 4.4 Populations and evolution · Explain · 5 marks

> Arctic foxes currently have white fur that camouflages them against snow. They are predators that hunt lemmings, but they are also preyed upon by wolves and eagles.

## Mark scheme (5 marks)

1. There is variation in fur colour within the fox population (e.g. some foxes have white fur and some have brown fur)
2. This variation is caused by (random) mutation / is inherited / genetic
3. White-furred foxes are more easily seen (less camouflaged) against bare brown ground and are therefore more likely to be predated / less likely to survive
4. Brown-furred foxes are better camouflaged so are more likely to survive, reproduce and pass on the allele/gene for brown fur to their offspring
5. Over many generations, the proportion of foxes with brown fur increases / brown fur allele becomes more common in the population

## Key terms

- [natural selection](https://www.gradenine.co.uk/glossary/natural-selection)
- [population](https://www.gradenine.co.uk/glossary/population)

## Related

- [Revision notes for OCR A-Level Biology B — Advancing Biology (H422)](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/a-species-of-arctic-fox-lives-08a8a9d3) · Published by Druglandscape Ltd.