QUESTION 1 (3 marks)
a) Define genetic drift.
[1 mark]
b) Explain why genetic drift is usually high in populations affected by bottlenecks.
[2 marks]
QCAA guide · typeset solution
QCAA sample response and mark allocation
1a) | Genetic drift refers to changes in allele frequencies within a population that occur due to chance. | • provides an appropriate definition [1 mark] |
1b) | A population bottleneck is a random event that drastically reduces the size of a population. Because the survivors of a bottleneck event usually do so by chance (as opposed to by having advantageous alleles), the allele frequencies of the surviving population are usually very different from the parent population due to sampling error. | • recognises that a bottleneck reduces the size of a population [1 mark] • explains why genetic drift is higher in populations affected by bottlenecks [1 mark] |
QCAA sample response and marking criteria reproduced from the official guide.
Compare your working with the guide above.