26 9 Biodiversity is monitored by conservationists. Biodiversity can be calculated using the formula D N N n n = − − ∑ ( ) ( ) 1 1 (a) Give the symbol in this formula that represents the total number of organisms of all species. (1) .................................................................................................................................................................................................................................................................................... (b) The photograph shows a hedge. (Source: © 1000 Words/Shutterstock) Many fields in the UK are separated by hedges. Conservationists investigated biodiversity in hedges of different ages. Hedges of different ages were sampled at random and the number of species of woody plants was counted. The graph shows the results of this investigation. 1200 1000 800 600 400 200 0 10 9 8 7 6 5 4 3 2 1 0 Age of hedge / years Mean number of species of woody plants in 30 m of hedge 27 Turn over Analyse the data to explain why conservationists object to the destruction of hedgerows to increase the size of fields. 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(c) State why random sampling was used in this investigation. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 28 (d) The conservationists observed that the plants in older hedges contained more wood than the plants in younger hedges. Wood consists of xylem tissue. (i) Give an advantage for older plants of containing more wood. 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(ii) Describe a method to show that the stem of an older plant contains more wood. 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The student used potatoes of different ages to test this hypothesis. Justify each step of a method the student could use to compare the water potential of potato tissue of different ages. 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(Total for Question 9 = 15 marks)