Conservationists want to estimate the population size of great crested newts (Triturus cristatus\textit{Triturus cristatus}Triturus cristatus) in a local wetland reserve using the capture-recapture method.
In the first sample, they capture 848484 newts, mark them on their dark-coloured backs with a small dot of non-toxic, dark-coloured waterproof paint, and release them back into the pond.
One week later, they return and collect a second sample of 909090 newts. Of these, 141414 are found to have the mark.
Estimate the population size of the great crested newts in this wetland reserve 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 sampleSuggest why the conservationists chose to use a small dot of dark, non-toxic paint on the dark backs of the newts rather than a bright, reflective plastic tag.
111 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.