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AP Biology
Evolution Unit, Chapter 15
Reading Guide
CHAPTER 15
Mechanisms of Evolution
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OBJECTIVES
 Explain the mechanism for evolutionary change proposed by Charles Darwin in On the Origin of
Species.
 Define evolution and adaptation.
 Explain what Darwin meant by “descent with modification.”
 Explain what evidence convinced Darwin that species change over time.
 Describe the three inferences Darwin made from his observations that led him to propose natural
selection as a mechanism for evolutionary change.
 Explain how an essay by the Rev. Thomas Malthus influenced Charles Darwin.
 Distinguish between artificial selection and natural selection.
 Explain why an individual organism cannot evolve.
 Explain how evidence from biogeography, paleontology, embryology, and molecular biology
supports the theory of evolution by natural selection.
 Explain the problem with the statement that Darwinism is “just a theory.” Distinguish between the
scientific and colloquial use of the word theory.
 Explain how microevolutionary change can affect a gene pool.
 State in your own words, the Hardy-Weinberg theorem.
 Write the general HW equation and use it to calculate allele and genotype frequencies.
 Explain the consequences of HW equilibrium.
 Demonstrate that a population requires only one generation of random mating to establish HW
equilibrium.
 Describe the usefulness of the HW model to population geneticists.
 List the conditions that must be met in order to maintain HW equilibrium.
 Explain how genetic drift, gene flow, mutation, and nonrandom mating and natural selection can
cause microevolution.
 Explain the role of population size in genetic drift.
 Distinguish between the bottleneck effect and the founder effect.
 Describe how sexual selection may lead to variation of phenotypes in a population.
 Explain what is meant by the statement ‘natural selection is the only agent of microevolution which
is adaptive’.
 Give the causes of genetic variation in a population.
 Explain how genetic variation may be preserved in a natural population.
 Explain the concept of relative fitness and its role in adaptive evolution.
 Describe what selection acts on and what factors contribute to the overall fitness of a genotype.
 Distinguish among stabilizing selection, directional selection, and disruptive selection.
 Explain how deleterious alleles may be maintained in a population.
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AP Biology
Evolution Unit, Chapter 15
Reading Guide
QUESTIONS
1.
Define evolution.
Why is evolution the unifying principle in biology?
2.
Define theory as it applies to science.
3.
What was the significance of Lamarck’s ideas?
4.
What was the mechanism he proposed?
5.
How does the present knowledge of molecular biology and genetics refute his mechanism.
6.
Summarize Darwin’s theory of evolution by natural selection.
7.
What was the significance of Darwin’s theory of evolution by natural selection?
8.
Natural selection occurs through interaction of two factors? What are they?
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AP Biology
Evolution Unit, Chapter 15
Reading Guide
9.
The basis for evolution by natural selection requires inheritable variation in a population.
Explain what this statement means.
10.
Explain the statement: ‘Natural selection acts on individuals, but populations evolve.’
11.
Define adaptation.
12.
What is the difference(s) between natural selection and adaptation?
13.
What is the raw material on which mechanisms of evolution act upon?
14.
What does it mean to say a population evolves?
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AP Biology
Evolution Unit, Chapter 15
Reading Guide
HARDY-WEINBERG THEOREM
POPULATION
GENE POOL
ALLELE FREQUENCY
GENOTYPE FREQUENCY
HARDY-WEINBERG EQUATION
HARDY-WEINBERG EQUILIBRIUM
REQUIRED CONDITIONS FOR HARDY-WEINBERG EQUILIBRIUM
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AP Biology
Evolution Unit, Chapter 15
Reading Guide
1.
What is the significance of Hardy-Weinberg equilibrium?
2.
If all of the above conditions hold, how many generations are required for a population to reach
HW equilibrium?
3.
What do deviations from HW equilibrium indicate?
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AP Biology
Evolution Unit, Chapter 15
Reading Guide
MECHANISMS OF EVOLUTIONARY CHANGE
Summarize the effect of each of the following on allele frequencies in a population.
MUTATIONS
GENE FLOW
GENETIC DRIFT
NON-RANDOM
MATING
NATURAL
SELECTION
4.
Why is genetic drift more apparent in small populations?
5.
What is the net affect of a population bottleneck?
6.
Define founder’s effect.
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AP Biology
Evolution Unit, Chapter 15
Reading Guide
7.
Which mechanism of evolution results in adaptation to the environment?
8.
Define fitness. How is fitness determined?
9.
Why do phenotypic variations in a population generally resemble a bell-curve?
TYPE OF NATURAL
SELECTION
EFFECT AND EXAMPLE
STABILIZING
SELECTION
DIRECTIONAL
SELECTION
DISRUPTIVE
SELECTION
SEXUAL
SELECTION
10.
Why, do you think, Darwin devoted an entire book to sexual selection?
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AP Biology
Evolution Unit, Chapter 15
Reading Guide
11.
If natural selection tends to reduce variation, then how is variation preserved with the
population?
12.
Summarize how each of the following act to maintain genetic variation or contribute to
evolutionary change in populations.
NEUTRAL MUTATIONS
SEXUAL
RECOMBINATION
GENE DUPLICATION
HETEROZYGOTE
ADVANTAGE
13.
Explain the following statements in order to address the question: Why can’t evolution fashion
perfect organisms?
a) Evolution is limited by historical constraints.
b) Adaptations are often compromises.
c) Chance and natural selection interact
d) Selection can edit only existing variations.
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