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21 Cards in this Set

  • Front
  • Back
Directional Selection
One extreme is selected for.
Stabilizing Selection
Medium values are selected for.
Disruptive Selection
Middle values are selected against. Can create two different species.
Anagenesis
Genetic changes through time within a population.
Cladogenesis
Diversification among populations (speciation, branching evolution)
Clade
The complete set of species descended from a common ancestor. Hierarchial.
Definition of species under the Biological species concept
Group of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.
Definition of species under evolutionary species concept
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.
Cryptic Species
Species that differ very subtly in observable traits but which are isolated.
Allopatric Speciation
Occurs as the result of complete geographic separation of populations
Peripatric Speciation
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.
Parapatric speciation
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.
Sympatric Speciation
The evolution of reproductive isolation within a population (where the potential for gene flow is very high)
Reinforcement
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.)
Vicariance
Speciation by a physical barrier that splits one population into two
Node
Where one ancestral lineage splits into two or more derived lineages
Taxon
Any named group of organisms
Polytomy
A node with >2 derived lineages
Homology
Similarity that results from inheritance of traits form a common ancestor
Homoplasy
Similarity that results from factors other than common ancestry (Convergent and Parallel evolution)
Plesiomorphy
Shared ancestral traits.