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Mechanisms of Evolution
Concept 4: Analyzing the evolution of populations through Hardy-Weinberg (microevolution)
Chapter 23 in Campbell, pg 155-158 in Holtzclaw
The Evolution of Populations
You must know:
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How mutation and sexual reproduction each produce genetic variation
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The conditions for Hardy-Weinberg Equilibrium
How to use the Hardy-Weinberg equation to calculate allelic frequencies, to test whether a population is
evolving.
Genetic Variation
Preservation of Genetic Variation
 Diploidy
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Heterozygote advantage
What alters allele frequencies?
 Three major factors:
Natural Selection – causes adaptive evolution
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Relative Fitness
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Three ways natural selection can work:
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Directional selection
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Disruptive selection
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Stabilizing selection
In what sense is natural selection more “predictable” than genetic drift?
Introducing…The Hardy-Weinberg Principle!
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Clarifies the factors that alter allele frequency
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A non-evolving population is in Hardy-Weinberg equilibrium.
Conditions for Hardy-Weinberg Equilibrium:
The Hardy-Weinberg Formula
p2 + 2pq + q2 = 1
where p + q = 1
In a certain population of 1000 fruit flies, 910 have red eyes while the remainder have sepia eyes.
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The sepia eye trait is recessive to red eyes.
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How many individuals would you expect to be homozygous for red eye color?
Hint: The first step is always to calculate q2!
Start by determining the number of fruit flies that are homozygous recessive…