Scientists use capture-recapture to estimate the number of moths in an orchard.
In the first sample, they catch 54 moths, mark each one and release them back into the orchard. They leave enough time for the marked moths to mix with the other moths.
In the second sample, they catch 45 moths. 9 of these moths are marked.
Calculate the estimated number of moths in the orchard.
The scientists later find that the marks had rubbed off some of the moths before the second sample was taken.
Explain whether the true number of moths in the orchard is likely to be higher or lower than your answer to (a).
109 exam-style questions on OCR GCSE Biology 6.1 Monitoring and maintaining the environment, covering 6.1.1 Field investigation of distribution and abundance, 6.1.2 Human interactions and biodiversity, 6.1.3 Maintaining biodiversity, and 6.1.4 Environmental change and distribution of organisms. Each one has a worked solution and a mark scheme showing where the marks go.