# Describe how the capture-recapture method is used to estimate the size of a population of beetles living in a woodland.

> OCR GCSE Biology A: Gateway Science (J247) — B6.1 Monitoring and maintaining the environment · Describe · 4 marks

> A student wants to find out how many ground beetles live in a woodland area. The woodland covers a large area and it is not possible to count all the beetles directly.

## Mark scheme (4 marks)

1. Organisms (beetles) are captured and counted
2. The captured organisms are marked and released back into the habitat
3. Time is allowed for the marked beetles to redistribute/mix with the rest of the population before a second sample is captured
4. The number of marked individuals in the second sample is used to estimate the total population size (larger proportion of marked = smaller population; smaller proportion = larger population)

## Key terms

- [capture-recapture](https://www.gradenine.co.uk/glossary/capture-recapture)
- [population](https://www.gradenine.co.uk/glossary/population)

## Related

- [Revision notes for OCR GCSE Biology A: Gateway Science (J247)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-the-capture-recapture-method-is-f6ab8297) · Published by Druglandscape Ltd.