11 Turn over 5 An investigation was carried out to study the effect of alcohol concentration on heart rate in Daphnia. (a) Give one reason why some people believe that there are fewer ethical issues when using Daphnia for this investigation rather than using a species of mammal. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (b) In this investigation, Daphnia were placed into three groups of 10. Each group was placed in alcohol of a different concentration for five minutes. After five minutes, each Daphnia was removed from the alcohol and its heart rate recorded every 15 seconds for one minute. A mean for each concentration was calculated. The results are shown in the table. Alcohol concentration / mol dm−3 Mean Daphnia heart rate / beats per minute 0.00 221 0.17 176 0.34 97 (i) Give one reason why 10 Daphnia were used for each alcohol concentration. (1) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (ii) Explain why the Daphnia were left for five minutes in the alcohol before the heart rate was recorded. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 12 (c) Devise an investigation to find the lowest concentration of alcohol that has an effect on the heart rate of Daphnia. (5) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (Total for Question 5 = 9 marks)