Ecologists want to estimate the population size of ground beetles in a local woodland using the capture-recapture method.
In the first sample, they capture 404040 beetles, mark them with a small dot of non-toxic paint, and release them back into the woodland.
Five days later, they collect a second sample of 454545 beetles. Of these, 888 are found to have the mark.
Estimate the population size of the beetles on the woodland floor using the formula:
Estimated population size=Number in first sample×Number in second sampleNumber in second sample previously marked \text{Estimated population size} = \frac{\text{Number in first sample} \times \text{Number in second sample}}{\text{Number in second sample previously marked}} Estimated population size=Number in second sample previously markedNumber in first sample×Number in second sampleThe ecologists marked the beetles on the underside of their abdomen rather than on their wing cases. Suggest why they did this.
67 exam-style questions on OCR GCSE Biology 4.1 Ecosystems, covering 4.1.1 Cycling of materials in ecosystems, 4.1.2 Microorganisms in cycling materials, 4.1.3 The carbon and water cycles, 4.1.4 Factors affecting decomposition, 4.1.5 Levels of organisation in an ecosystem, 4.1.6 Abiotic and biotic factors affecting communities, 4.1.7 Interdependence and competition, 4.1.8 Trophic levels, 4.1.9 Pyramids of biomass, and 4.1.10 Efficiency of biomass transfers. Each one has a worked solution and a mark scheme showing where the marks go.