| Criteria | Marks |
|---|
| • Demonstrates a thorough understanding of TWO mechanisms by which gene pools change<br>• Relates changes in the gene pool to evolution | 5 |
| • Links changes in the gene pool to evolution<br>AND<br>• Demonstrates a thorough understanding of ONE mechanism by which gene pools change<br>OR<br>• Demonstrates some understanding of TWO mechanisms by which gene pools change | 3–4 |
| • Outlines ways in which gene pools can change<br>OR<br>• Links changes in gene pools to evolution | 2 |
| • Provides some relevant information | 1 |
Sample answer:
A gene pool is the total genetic diversity of a population – it results in variation of phenotypes and provides the basis for natural selection. When the gene pool of a population changes evolution has occurred. Gene pools may change as a result of mutation, gene flow and genetic drift. Gene flow is the movement of alleles into or out of a population. For example a migrant animal may add new alleles when it reproduces with individuals in the population. Genetic drift is a change in allele frequency as a result of random selection of alleles. This is especially marked in a small, remnant population. The few remaining individuals that survive carry a small sample of the alleles in the original population.