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27 Cards in this Set
- Front
- Back
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Speciation |
the process by which one species splits into two |
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microevolution |
changes overtime in allele frequencies in a population |
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macroevolution |
the broad pattern of evolution above the species level |
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biological species concept |
a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile, offspring |
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morphological species concept |
characterizes a species by body shape and other structural features and can be applied to asexual and sexual organisms |
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ecological species concept |
views a species in terms of its ecological niche |
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ecological niche |
sum of how members of the species interact with the nonliving and living parts of their environment |
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phylogenetic species concept |
defines a species as the smallest group of individuals that share a common ancestor |
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gene flow |
the transfer of alleles into or out of a population |
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reproductive isolation |
the existence of biological barriers that impede members of two species from interbreeding and producing viable, fertile offspring |
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hybrids |
- offspring that result from an inter specific mating - reproductive isolation limits gene flow between species and the formation hybrids |
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Prezygotic barriers |
- "before the zygote" - block fertilization from occurring |
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Types of Prezygotic barriers |
-impeding members of different species from attempting to mate - preventing an attempted mating from being completed successfully - hindering fertilization if mating is completed successfully |
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Postzygotic barriers |
a reproductive barrier that prevents hybrids zygotes produced by two different species from developing into viable, fertile adults |
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allopatric speciation |
gene flow is interrupted when a population is divided into geographically isolated subpopulations |
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sympatric speciation |
speciation occurs in populations that live in the same geographic area |
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polyploidy |
- a chromosomal alteration in which the organism possesses more than two complete chromosome sets - result of an accident of cell division |
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autopolyploid |
an individual that has more than two chromosome sets that are all derived from a single species |
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allopolyploid |
a fertile individual that has more than two chromosomes sets as a result of two different species interbreeding and combining their chromosomes |
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hybrid zone |
region in which members of different species meet and mate, producing at least some offspring of mixed ancestry |
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Reinforcement |
strengthening of reproductive barriers-- hybrids gradually cease to be formed |
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Fusion |
weakening of reproductive barriers-- the two species fuse |
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Stability |
continued production of hybrid individuals |
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punctuated equilibria |
periods of apparent stasis punctuated by sudden change |
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speciation rates |
- punctuated pattern in the fossil record and evidence from lab studies suggests that speciation can be rapid - interval between speciation events can range from 4,000 year to 40,000,000 years |
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sister species |
pairs whose member species are each other's closest relative |
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geographic separation |
- different mutations arise - different selective pressures in differing environments act on the two populations - genetic drift alters allele frequencies. |
