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21 Cards in this Set
- Front
- Back
Directional Selection
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One extreme is selected for.
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Stabilizing Selection
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Medium values are selected for.
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Disruptive Selection
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Middle values are selected against. Can create two different species.
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Anagenesis
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Genetic changes through time within a population.
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Cladogenesis
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Diversification among populations (speciation, branching evolution)
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Clade
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The complete set of species descended from a common ancestor. Hierarchial.
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Definition of species under the Biological species concept
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Group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.
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Definition of species under evolutionary species concept
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Species are a single lineage of populations or organisms that maintains its identity from other such lineages and which has its own evolutionary tendencies and historical fate.
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Cryptic Species
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Species that differ very subtly in observable traits but which are isolated.
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Allopatric Speciation
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Occurs as the result of complete geographic separation of populations
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Peripatric Speciation
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Classic peripatric speciation involves the budding off of small populations at the edge of a species range. Genetic drift has large effects on the small population. Environmental differences are often involved.
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Parapatric speciation
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Speciation in which the new species forms from a population contiguous with the ancestral species’ range.
May involve a sharp environmental gradient with accordingly strong selection. |
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Sympatric Speciation
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The evolution of reproductive isolation within a population (where the potential for gene flow is very high)
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Reinforcement
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If hybrid offspring have low fitness (relative to non-hybrid offspring) there may be natural selection for traits that promote positive assortative mating (where individuals preferentially choose mates from their own population.)
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Vicariance
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Speciation by a physical barrier that splits one population into two
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Node
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Where one ancestral lineage splits into two or more derived lineages
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Taxon
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Any named group of organisms
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Polytomy
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A node with >2 derived lineages
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Homology
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Similarity that results from inheritance of traits form a common ancestor
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Homoplasy
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Similarity that results from factors other than common ancestry (Convergent and Parallel evolution)
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Plesiomorphy
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Shared ancestral traits.
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