Lect4-26March_v2

Lect4-26March_v2 - Todays Lecture Finish: what are species...

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Today’s Lecture • Finish: what are species • Speciation
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Quick Review • What is a species, according to the biological species concept? • What are the different types of isolating mechanisms between species?
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What are species Biological Species Concept Major Advantages • Many biologists would agree that interbreeding among populations is an important attribute of species (probably the most important) • Interbreeding separates “species” from other taxonomic units (conspecific individuals interbreed, heterospecific individuals do not)
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What are species Biological Species Concept First Major Problem • Hard to tell if putative species are reproductively isolated unless sympatric (living in same place)
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Basic Terms for Geographic Distribution of Species Allopatric (separate) Parapatric (adjacent) Sympatric (same place) species 1 species 2 species 1 species 2 species 1 species 2
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What are species Biological Species Concept Major Problems-1 • Hard to tell if putative species are reproductively isolated unless sympatric (living in same place) • Can bring species into lab to see if they will interbreed (or transplant them), but may be hard to get species to behave “naturally”
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What are species Biological Species Concept Related Problem • Biologists who follow BSC generally cannot tell whether allopatric populations are distinct species • Huge problem, because most closely-related species are allopatric! • Instead most utilize “diagnostic” differences between populations to recognize different species
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Species Concepts Biological Species Concept Second Major Problem • Species that are not closely related can interbreed (“hybridize”) in many cases Hybridization = mating between individuals of different species Introgression = hybridization leading to gene flow
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Speciation • Speciation is the general process by which new species arise • How speciation works depends (in part) on the geographic mode of speciation • Geographic mode depends on how new species are geographically situated
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Overview of Geographic Modes of Speciation Allopatric Parapatric Sympatric Ancestral species new species 1 new species 2 new species 1 new species 2 new species 1 new species 2 Ancestral species Ancestral species
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Allopatric Speciation Generally considered very straightforward, with two parts • Populations become geographically isolated • Reproductive isolating mechanisms evolve (i.e., prezygotic, postzygotic)
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This note was uploaded on 04/17/2010 for the course BIO 201 taught by Professor True during the Spring '08 term at SUNY Stony Brook.

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Lect4-26March_v2 - Todays Lecture Finish: what are species...

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