Which condition must be true for a capture-recapture estimate to be valid?
The marked animals are kept separate from the others until the second sample.
No animals are born, die, join or leave the population between the samples.
The second sample must contain more animals than the first sample caught.
Every animal in the population is caught and marked in the first 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.