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Population genetics
The study of evolution from a genetic point of view
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Microevolution
Evolution at the genetic level; defined as a change in the collective genetic material of a population
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Bell Curve
on a graph of the frequency of some variable, a curve that first rises and then falls, thus forming a bell-shaped curve
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Gene Pool
describes the total genetic information available in a population
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allele frequency
the proportion of gene copies in a population that is a given allele, expressed as a precentage
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Phenotype frequency
Equal to the number of individuals with a particular phenotype divided by the total number of individuals in the population
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Hardy-Weinberg principle
states that the frequency of alleles in a population does not change over generations unless outside forces act on the population
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Immigration
The movement of individuals into a population
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Emigration
The movement of indivduals out of a population
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Gene Flow
the process of genes moving from one population to another
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Genetic drift
phenomenon by which allele frequencies in a population change as a result of random events or chance
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Sexual selection
When females tend to choose the males they mate with based on certain traits
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Stabilizing selection
individuals with the average form of a trait have the highest fitness
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Disruptive selection
individuals with either extreme variation of a trait hoave grater fitness than individuals with the average form of the trait
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Directional Selection
individuals that display a more extreme form of a trait have a greater fitness than individuals with an average form of the trait
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Speciation
the process of species formation, results in closely related species
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Morphology
The internal and external structure and appearance of an organism, chief criterion for classifying it as a species
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biological species concept
states that a species is a population of organisms that can be successfully interbreed but cannot breed with other groups
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Geographic isolation
the physical separation of members of a population
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Allopatric Speciation
Occurs when species arise as a result of a geographic isolation
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Reproductive isolation
happens from barriers to successful breeding between population groups in the same area
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Prezygotic isolation
- occurs before fertilization
- also called premating isolation
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Postzygotic isolation
- Occurs after fertilization
- also called postmating isolation
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Sympatric speciation
occurs when two subpopulations become reproductively isolated within the same geographic area
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Gradualism
The idea that speciation occurs at a regular, gradual rate
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Punctuated equilibrium
a model of evolution in which short periods of drastic change in species, including mass extinctions and rapid speciation, are separated by long periods of little or no change
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