20 7 The photograph shows a wood mouse, Apodemus sylvaticus. (Source: © Eric Isselee/Shutterstock) A scientist measured the population size of these mice living in a woodland habitat. The scientist used the capture-mark-recapture method (CMR) to sample the population. This is the CMR method used by the scientist: ● randomly place mammal traps in the woodland for one day ● put a coloured band on a leg of each captured mouse (S1) ● release these marked mice ● after one week place mammal traps in the woodland again for one day ● count the number of mice captured (S2) ● count the number of mice with leg bands in this second sample (L). The table shows some of the results. Number of mice captured S1 S2 200 250 21 Turn over (a) The scientist calculated that the number of mice in the woodland was 1000, using the formula number of mice = S S L 1 2 × Determine the number of mice that had leg bands (L) in the second sample. (1) Answer .............................................................. (b) The diagram shows a section of the trap used by the scientist. food wire trap door board entrance Explain how the design of the trap is effective for capturing mice. 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They cannot maintain their body temperature and will die if left in the trap for a long period of time. Explain why wood mice cannot maintain their body temperature if left in the trap. 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(Total for Question 7 = 13 marks)