Week 22

Question 1

1. Define genetic drift and gene flow and recognize examples of each.

Answer 1

Genetic Drift: A random process that changes allele frequencies in a population due to chance events, often significant in small populations. Example: The bottleneck effect observed in black-footed ferrets, where only a few individuals survive, reducing genetic diversity.
Gene Flow: The movement of alleles between populations through migration of individuals or gametes. Example: The movement of pollen or seeds between plant populations.

Question 2

2. Describe and contrast how genetic drift and gene flow can cause allele frequencies in a population to change over time.

Answer 2

Genetic Drift: Causes random changes in allele frequencies, especially in small populations, often reducing genetic variation and potentially lowering average fitness (e.g., extinction vortex in small populations).
Gene Flow: Introduces new alleles into a population or homogenizes genetic variation between populations, potentially increasing genetic diversity and fitness in some cases or inhibiting local adaptation in others.

Question 3

3. Describe the effect that genetic drift and gene flow have on average fitness and genetic variation in a population.

Answer 3

Genetic Drift:
Effect on Fitness: Often random but can decrease average fitness due to loss of beneficial alleles.
Effect on Genetic Variation: Decreases genetic variation within populations.
Gene Flow:
Effect on Fitness: Can increase fitness by introducing beneficial alleles or decrease fitness by introducing maladaptive alleles.
Effect on Genetic Variation: Increases genetic variation within populations but reduces differences between populations.

Question 4

4. Explain how the presence or absence of gene flow into a population can influence how genetically similar it is to other populations.

Answer 4

Presence of Gene Flow: Makes populations more genetically similar by mixing alleles.
Absence of Gene Flow: Allows populations to diverge genetically due to independent evolutionary processes like mutation, selection, or drift.

Question 5

5. Predict whether gene flow into a population will help or inhibit the population’s capacity to adapt to local conditions.

Answer 5

Help: Gene flow can introduce new genetic material that provides raw variation for selection to act upon, aiding adaptation, especially after bottleneck events.
Inhibit: If gene flow introduces maladaptive alleles or prevents local adaptation by homogenizing differences, it may hinder the population’s ability to adapt.

Question 6

Gene flow is most likely to:
A. Increase genetic diversity in recipient
population
B. Decrease genetic diversity in recipient
population

Answer 6

A, INCREASE