23.3 Natural Selection, Genetic Drift, and Gene Flow

Question 1

Chance events can cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small populations. What are the 3 effects that could happen.

Answer 1

• Can cause allele frequencies to change at random.
• Can lead to a loss of genetic variation within a population.
• Can cause harmful alleles to become present

Question 2

What are two examples of genetic drift? Define them.

Answer 2

• The Founder Effect: A few individuals become isolated from a larger population, and this small group may establish a new population, whose gene pool differs from the source population.
• The Bottleneck Effect: A sudden change in the environment such as a fire, or flood, may drastically reduce the size of the population. By chance alone, certain alleles my be underrepresented or absent, and some newer alleles may be present, making the group of survivors genetically different from the original population.

Question 3

What is Gene Flow?

Answer 3

It is the transfer of alleles or genes from one population to another.

Question 4

What are the 4 effects of Gene Flow?

Answer 4

• Tend to reduce the genetic differences between populations.
• Results in two populations combining into single population with a common gene pool.
• Can transfer alleles that improve the ability of populations to adapt to local conditions.
• Mating is more common between members of populations that previously had very little contact, leading to an exchange of alleles and fewer genetic differences between populations,