22 8 The photograph shows a fruit fly, Drosophila. (Source: © Roblan/Shutterstock) Species of Drosophila live in a range of habitats in different parts of the world. The geographic distribution of these species ranges from regions with low temperatures to regions with high temperatures. The graph shows the effect of temperature on the percentage fertility of male flies of two species of Drosophila, D. simulans and D. melanogaster. 100 90 80 70 60 50 40 30 20 10 0 10 11 12 13 14 15 16 Growth temperature / °C Percentage fertility (%) D. simulans D. melanogaster Turn over 23 (a) The effect of low temperature on fertility is often compared using the temperature that results in 50% fertility. Determine the difference in these temperatures for the two species. (1) Temperature difference .............................................................. (b) Scientists also collected data from the two species about the effect of both high and low temperature on the viability of eggs and fertility of male flies. An egg is viable if it develops into an adult. The table shows the effects of temperature on the viability of eggs and fertility of males, for the two species of Drosophila. Species Lowest temperature / °C Highest temperature / °C at which eggs are viable at which males are fertile at which eggs are viable at which males are fertile D. melanogaster 10 12 32 30 D. simulans 10 11 31 28 (i) Give the relationship between temperature and the viability of eggs and fertility of males. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 24 *(ii) Another group of scientists recorded the courtship song of male D. melanogaster and male D. simulans. The male flies vibrate their wings producing a courtship song to attract females. The courtship song is produced in pulses. The interval between pulses and the duration of each pulse are shown in the table. Species Mean interval between pulses / ms Duration of pulse / s D. melanogaster 34.1 1.6 D. simulans 48.9 3.4 Discuss how the data provides evidence for the geographical distribution and type of speciation of the two species of Drosophila. Use the data from tables for temperature and for courtship song. 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(Total for Question 8 = 8 marks) TOTAL FOR PAPER = 80 MARKS 26 BLANK PAGE 27 BLANK PAGE 28 BLANK PAGE