27_SpeciationI_2010-1

27_SpeciationI_2010-1 - Mystery of Mysteries Speciation...

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“Mystery of Mysteries”
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Speciation, the origin of new species, is at the focal point of evolutionary theory Microevolution consists of adaptations that evolve within a population, confined to one gene pool Macroevolution refers to evolutionary change above the species level Speciation
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The Biological Species Concept Members of a biological species are reproductively  compatible , at least potentially; they cannot interbreed with other populations. Similarity between different species. Diversity within a species.
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Reproductive Isolation Reproductive isolation is the existence of biological factors (barriers) that impede two species from producing viable, fertile hybrids Barrier here
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Reproductive Isolation – increases  with time of separation
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Reproductive Isolation –  Dobzhansky-Muller model
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Gene flow – the movement of gametes or individuals  between populations resulting in genetic changes in a  population (for example, changes in allele frequencies) Reproductive Isolation
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What can act as barriers to gene flow ? What can prevent organisms from mating with the ‘wrong’ type? The   critical issue is the reduction of gene flow between populations, so that populations can diverge in allele frequencies -by genetic drift -by natural selection Reproductive Isolation
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Gene Flow in VariousTaxa Nm = number of migrants per generation
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The Biological Species Concept Premating Postmating Postzygotic Prezygotic “Species are groups of actually or potentially
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27_SpeciationI_2010-1 - Mystery of Mysteries Speciation...

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