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17 Cards in this Set
- Front
- Back
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Frequency-dependent selection |
fitness of a genotype depends on its frequency in a population |
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clinical variation |
gradual change in phenotype across a geographical gradient |
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Stabilizing selction |
preserves average characteristics of a population by favoring average individuals, reduces variation |
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disruptive selection |
favoring individuals at both extremes (not the mean)
increases variation
advantagagous to heterozygote |
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directional selection |
favoring individuals in one direction; shifts mean
reduces variation |
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fitness |
reproductive contribution of a phenotype to subsequent generations relative to the contributions of other phenotypes |
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hybridize |
to interbreed |
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reinforcement |
evolution of enhanced reproduction
isolation between populations
due to natural selection for greater isolation |
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biological species concept |
actually or potentially interbreeding natural populations that are reproductively isolated from other such groups |
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polyploidy |
most common means of sympatric speciation
duplication of sets of chromosomes within individual |
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autopolyploidy |
polyploidy within a single species |
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habitat isolation |
when individuals of different species evolve genetic preference for different habitats in which they live or mate.
may never come in contact during mating periods
prezygotic |
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temporal isolation |
many organisms have distinct mating seasons
if too closely related species breed at different times the two may never have an opportunity to hybridize
prezygotic |
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low hybrid zygote viability |
hybrid zygotes may fail to mature normally, either dying during development or developing such severe abnormalities that htey cannot mate as adults
prezygotic |
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prezygotic |
before fertilization |
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low hybrid adult viability |
hybrid offspring may simply have lower survival than offspring resulting from within populations
prezygotic |
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hybrid infertility |
hybrid may mature normally but be infertile
example: mules
postzygotic |
