Researchers are estimating the population of field voles in a heathland reserve. They catch 48 field voles, mark them harmlessly and release them. After the marked voles have had time to mix evenly back into the population, the researchers catch 60 field voles. Twelve of these have a mark.
Calculate the estimated population of field voles in the reserve.
Explain how the estimate would be affected if some marks rubbed off before the second sample.
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.