# A conservation team is monitoring a population of water voles living along a riverbank. They carry out a mark-recapture study over two seasons and notice that the estimated population size has declined significantly between the first and second season. Explain how a reduction in genetic diversity within this water vole population could reduce its long-term sustainability.

> OCR A-Level Biology A (H420) — 6.6 Populations and sustainability · Explain · 4 marks

> Water voles are one of the UK's most rapidly declining native mammals, largely due to habitat loss and predation by introduced American mink. Conservation efforts include captive breeding programmes and habitat restoration schemes along river corridors.

## Mark scheme (4 marks)

1. A smaller population has fewer alleles / less variation in alleles at each gene locus
2. Increased likelihood of inbreeding, leading to expression of harmful recessive alleles
3. The population has reduced capacity to adapt to environmental changes such as new pathogens or changing climate
4. A novel disease or environmental change could eliminate the entire population because individuals are genetically similar / susceptible

## Key terms

- [mark-recapture](https://www.gradenine.co.uk/glossary/mark-recapture)
- [genetic diversity](https://www.gradenine.co.uk/glossary/genetic-diversity)
- [sustainability](https://www.gradenine.co.uk/glossary/sustainability)

## Related

- [Revision notes for OCR A-Level Biology A (H420)](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-conservation-team-is-monitoring-a-61c285ea) · Published by Druglandscape Ltd.