Chapter 5: The Genetical Theory of Natural Selection

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25 Terms

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Historical contingency
________ is the outcome of evolution that is determined by where the population begins.
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Selective sweeps
________ are situations in which a beneficial mutation spreads through a population.
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Standing genetic variation
_________ is when an allele that is present in the population is initially not favored, but then suddenly becomes beneficial when conditions change.
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beneficial allele
When a(n) ________ spreads by selection, the final outcome is that it becomes fixed (it reaches a frequency of 1).
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evolutionary trade-off
When there is a(n) _________, natural selection favors the allele that has the highest fitness overall.
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W
____{answer is the variable}____= (probability that the individual survives to maturity)* (expected number of offspring if the individual does survive)
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strength of selection
The ________ is determined by fitness differences.
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positive selection
The rate at which ________ causes an allele frequency to evolve depends on dominance.
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A(n) individual who leaves 2 offspring has a fitness of __[number]____.
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positive frequency dependence
When frequency-dependent selection favors the most common allele, this is called ___________.
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deleterious alleles
Balancing selection is fundamentally different from the selection on beneficial and ________, which acts to remove genetic variation.
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Relative fitnesses
________ play a critical role in determining the speed and outcome of evolution by natural selection.
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Multiple niche polymorphism
________ is when different genotypes specialize in different ecological niches.
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Genetic correlations
________ occur when two traits tend to be inherited together.
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adaptive landscape
The ________ is a plot created by Wright that tells us how the population will evolve.
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absolute fitness
A(n) individual's ________ is the number of zygotes (offspring) produced over its lifetime.
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dominant
A(n) allele is _____ if it causes the same phenotypic effect when heterozygous as when homozygous.
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Deleterious mutations
________ are mutations that decrease fitness.
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Fitness components
________ are one of several events in the life cycle of many organisms that contributes to the determination of fitness, such as survival to maturity, mating success, and fecundity.
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genetic variance
The increase in mean fitness per generation is equal to the ________ for fitness itself.
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Overdominance
________ occurs when the heterozygote has higher fitness than both homozygotes.
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Natural selection
________ causes populations to evolve so that they become better adapted to their environment: the average survival and reproduction of individuals increase through time.
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Positive selection
________ ultimately eliminates genetic variation, so other evolutionary factors must be responsible for maintaining all the genetic variation in nature.
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genetic variation
Balancing selection preserves ________, and in most cases, the population will evolve to the same allele frequency no matter where it begins.
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Positive selection
________ is the selection for an allele that increases fitness.