26 7 (a) (i) The diagram shows the transfer of energy through a grassland food chain. All values are given in kJ m−2 yr−1. Decomposers Secondary consumer Producer = 1.4 × 105 Primary consumer 9.1 × 102 3.9 × 102 7.6 × 103 3.1 × 103 4.4 × 104 8.4 × 104 energy loss Calculate the percentage efficiency of the energy transfer from the producer to the primary consumer. (2) Answer.............................................................. Turn over 27 (ii) Explain the differences in the efficiency of energy transfer between the trophic levels in a food chain. 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Hedgerows provide a habitat for many species of plants and animals. Some animals that live in hedgerows eat pests of crops and some pollinate crop plants. The crop yield, temperature and wind speed were measured across the field starting at the hedge. These factors and the crop yield are shown as a relative percentage compared with the centre of the field in the graph. Relative percentage compared with the centre of the field (%) 30 20 10 0 −10 −20 −30 25 20 15 10 5 Key crop yield temperature wind speed Distance from hedgerow / m Turn over 29 Analyse the information to comment on the value of conserving hedges around fields used for growing crops. 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(Total for Question 7 = 11 marks)