7 Turn over 3 Adult female cabbage aphids (Brevicoryne brassicae) undergo either asexual reproduction or sexual reproduction depending on the time of year. The photograph shows some cabbage aphids on a cabbage leaf. Source: © Denis Crawford/Alamy Stock Photo Some of the boxes in the diagram show the number of chromosomes present in a single cell from a particular stage of each of the alternative methods of reproduction. 16 16 Asexual reproduction in spring and summer Sexual reproduction in autumn and winter Growth Growth Sperm Nymph Juvenile Fertilisation Adult female Adult male Eggs (a) (i) Complete the empty boxes in the diagram to show the number of chromosomes present in a single cell at that stage of reproduction. (2) (ii) Label the arrows on the diagram with the letter M to show where meiosis takes place. . (1) 8 (b) Explain why a juvenile aphid is genetically identical to its parent. (3) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (c) (i) Complete the table with a  or × to compare the events during mitosis and meiosis. The first row in the table has been completed for you. (3) Event Mitosis Meiosis I Meiosis II chromosomes shorten and thicken   × homologous chromosomes pair together crossing over can cause genetic variation homologous chromosomes separate sister chromatids separate 9 Turn over (ii) Which of the following increases the number of different alleles in a population? (1) A crossing over B gene mutation C independent assortment of chromosomes during nuclear division D random fusion of gametes (Total for Question 3 = 10 marks)