Lecture_3_Origin_of_Species

Lecture_3_Origin_of_Species - 6/15/2011 What is a species?...

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6/15/2011 1 Species and Their Formation LS1: Summer Session A June 24, 2011 What is a species? The concept of “species” is one that is easy to grasp, but difficult to define Clearly, species are real biological entities Same species or different? Can you really identify species when you see them? Is it important to know what a species is? Red wolf Gray wolf Coyote Defining species Morphological species concept : Species are organisms that look alike
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6/15/2011 2 Problems with the morphological species concept Defining species Biological species concept : Species are “groups of actually or potentially interbreeding natural populations that are reproductively isolated from other such groups.” Ernst Mayr (1904 2005) Problems with the biological species concept Defining species Lineage species concept : A species has its own evolutionary history distinct from other species What is a species? Evolutionarily independent population(s), with reproductive isolation between species In the absence of gene flow, genetic differences between species arise because mutation, selection and drift act independently on a species regardless of what is happening in other populations Reproductive isolation is central to driving speciation Gene flow homogenizes populations A lack of gene flow (i.e., reproductive isolation) can lead to speciation
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6/15/2011 3 How do new species arise? An individual with a new allele that immediately makes it reproductively incompatible with its cohort could not reproduce, and therefore would not lead to a separate lineage The Dobzhansky-Muller model of speciation
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Lecture_3_Origin_of_Species - 6/15/2011 What is a species?...

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