AP BIOLOGY
FORCES OF EVOLUTION
READ:

CH 23.1 (pp. 469-472) and CH 23.3-23.4 (pp. 476-485)
CAMPBELL BIOLOGY ONLINE TASKS:

View the BioFlix: Mechanisms of Evolution animation
QUESTIONS
1. Explain why genetic variation is a prerequisite for evolution.
2. What factors can produce genetic variation among
populations?
3. What is a mutation? Identify the three possible outcomes of a
mutation.
4. Discuss the potential evolutionary impact of a mutation in a
somatic cell versus a gamete cell.
5. Identify the THREE mechanisms that contribute to the
shuffling of genes during sexual reproduction and briefly
explain how each leads to genetic variation
6. Identify the THREE mechanisms that may directly alter allele
frequencies and thus cause most evolutionary change. Identify which of these mechanisms is considered
random processes.
7. Discuss how genetic drift affects allele frequency.
8. Distinguish between the bottleneck effect and the founder effect. Provide an example to illustrate both types
of genetic drift.
9. Explain why genetic drift …
 Is significant in small populations
 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 fixed
10. Why does less genetic drift take place in a large population?
11. Discuss how gene flow affects allele frequency.
12. Describe how gene flow can act to reduce genetic differences between adjacent populations.
13. Distinguish between genetic drift from gene flow in terms of (a) how they occur and (b) their implications for
future genetic variation in a population.
14. What is the relative fitness of a sterile mule? Explain
answer.
15. Distinguish among directional, disruptive, and
stabilizing selection. Give an example of each mode
selection.
16. Discuss how sexual selection affects the allele
frequency of a population.
17. Distinguish between intrasexual selection and
intersexual selection.
Created by Mark Eberhard
Adapted from work by Lee Ferguson & David Knuffke
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Explain how female preferences for showy male traits may benefit the female.
Explain how diploidy can protect a rare recessive allele from elimination by natural selection.
Describe how heterozygote advantage might work to benefit an organism. .
List four reasons why natural selection cannot produce perfect organisms.
Explain how natural selection is the only evolutionary mechanism that consistently leads to adaptive evolution.
Although the assumptions of the Hardy-Weinberg equilibrium are never met completely in real populations, the
genotype frequencies of many populations do not deviate significantly from H-W expectations. Explain why.
KEY TERMS: Here is a list of key terms and concepts you will hear about and see during the chapter readings. Get
to know them!
Microevolution
Genetic Drift
Gene Flow
Directional Selection
Gene Pool
Founder’s Effect
Mutation
Disruptive Selection
Alleles
Bottleneck Effect
Crossing Over
Stabilizing Selection
Allele Frequency
Population
Independent Assortment
Heterozygote Advantage
Intrasexual selection
Interasexual selection
Sexual dimorphism
Diploidy
SUPPLEMENTARY RESOURCES:
Interactives
 Genetic Drift Simulation at the University of Arizona
http://www.biology.arizona.edu/evolution/act/drift/drift.html
 Brief video tutorial about genetic drift (Lego people!)
https://www.youtube.com/watch?v=Q6JEA2olNts&safe=active
 UC Berkeley’s Understanding Evolution: Genetic Drift
http://evolution.berkeley.edu/evolibrary/article/evo_24
 PBS’ Evolution site: The Founder Effect and Polydactyly
http://www.pbs.org/wgbh/evolution/library/06/3/l_063_03.html
Lectures
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Bozeman Biology’s “Genetic Drift” video.
Bozeman Biology’s “Evolution Continues” video.
Created by Mark Eberhard
Adapted from work by Lee Ferguson & David Knuffke
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