7_Speciation

7_Speciation - Speciation (24.1 - 24.2) Two basic patterns...

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Speciation (24.1 - 24.2)
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2 Two basic patterns of speciation Anagenesis (phyletic or vertical evolution) transforms one species into another Cladogenesis (branching evolution) is the splitting of a gene pool, giving rise to one or more new species
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Anagenesis Cladogenesis
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4 Darwin’s “Mystery of Mysteries” How do new species appear? QuickTime™ and a Sorenson Video 3 decompressor are needed to see this picture.
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5 Species = fundamental unit of organization in nature Ornithologist Ernst Mayr identified 137 birds in Papua New Guinea Native Papuans already had names for 136 species
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6 Species Concepts Morphological: defines a species by structural features Paleontological: focuses on morphologically discrete species known only from the fossil record Ecological: views a species in terms of its ecological niche Phylogenetic: defines a species as a set of organisms with a unique genetic history Biological: actually or potentially capable of interbreeding
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7 Biological species concept is most popular, but does not work in all situations Fossils Asexual taxa Taxa not amenable to breeding studies
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8 No species concept works in all situations Many species have few distinguishing morphological characters Often have too little information to apply ecological or phylogenetic concepts Fossils rarely distinguish taxa down to the species level….
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9 Two types of reproductive barriers 1) Prezygotic 2) Postzygotic
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10 Pre zygotic barriers impede mating or hinder fertilization if mating does occur: Habitat isolation ( wrong place ) Temporal isolation ( wrong time ) Behavioral isolation ( no attraction ) Mechanical isolation ( can’t copulate/pollinate ) Gametic isolation ( can’t fertilize )
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This note was uploaded on 09/27/2008 for the course BISC 120Lg taught by Professor 11:00-01:50pm during the Fall '06 term at USC.

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7_Speciation - Speciation (24.1 - 24.2) Two basic patterns...

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