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19 Cards in this Set
- Front
- Back
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Protobionts
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droplets of segregated chemicals which were the beginnings of life
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punctuated equilibrium
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changes in organismal form happened very quickly and were maintained thereafter over long periods of time
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molecular clocks hypothesis
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genetic mutations occur in a genome at a constant, linear rate
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stabilizing selection
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extremes at both ends of a phenotype are eliminates, resulting in less genetic variability
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directional selection
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one extreme is selected against but not the other so that the average in the population moves in one direction
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disruptive (diversifying) selection
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favors both extremes but selects against the averages
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sexual selection
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force exhibited by a member of the same species of the opposite sex - favors superior mates to create successful offspring
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prezygotic barrriers
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ecological, temporal, behavioral, or mechanical factors, or physiological incompatibility of gametes
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postzygotic barriers
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inviability or sterility of hybrid organisms from the interbreeding of two species
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allopatric isolation
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one population separated into two distinct populations by some geographic barrier
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sympatric isolation
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individuals within a population acquire distinctively different traits while in the same geographic area
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paraptric speciation
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two populations are able to interbreed along a border, but their mating is negligible in comparison to the mating of each population
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speciation
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when part of the population branches off and becomes a new species
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genetic drift
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a change in allele frequencies that is due to chance events
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bottleneck
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when genetic drift dramatically reduces population size
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gene flow
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the change in allele frequencies in the next generation
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honest indicators
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sexually selected traits that are the result of female choice
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artificial selection
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when humans become the agents of natural selection
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convergent characters
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similar characteristics in two species that do not share a common ancestor
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