genetic drift and gene flow - unit 4 AOS 2

Question 1

genetic drift

Answer 1

Genetic drift results from a random event that dramatically alters a population’s gene pool and occurs through either the bottleneck effect or the founder effect.

Question 2

bottle neck effect

Answer 2

the reduction in genetic diversity that occurs when a large proportion of a population is removed due to a chance event. Due to the severe reduction in population size, many individuals carrying unique alleles can be lost. Therefore, the new population has lower genetic diversity than the pre-disaster population.

Question 3

gene flow

Answer 3

• Gene flow is the movement of alleles between interbreeding populations. When individual organisms move or migrate between populations, they are transferring their alleles from one gene pool to another if they interbreed.
• Migration can occur when populations are physically close together, or due to external forces such as the clearing of a geographical barrier between populations. The migration into and out of a population is known as immigration and emigration, respectively.

Question 3

founder effect

Answer 3

• The founder effect occurs when a small group breaks away from a larger population to colonise a new territory
• As this population subset does not have the same degree of diversity as a larger population, it is subject to more genetic drift
• Consequently, as this new colony increases in size, its gene pool will no longer be representative of the original gene pool

Question 4

effect of gene flow on genetic diversity

Answer 4

• When new alleles are brought into a population through immigration, the genetic diversity in a population increases. This increase is more pronounced in smaller populations since they have a smaller gene pool to begin with. In larger populations, the immigration of new alleles into the population does not significantly affect the gene pool.
• emigration removes alleles from a population’s gene pool, decreasing genetic diversity. Once again, the effects of emigration are more pronounced in smaller populations compared to larger populations.