Lecture 7 - Chapter 24, Sections 1 and 2 - Speciation

Lecture 7 - Chapter 24, Sections 1 and 2 - Speciation - Two...

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Speciation 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 Anagenesis Cladogenesis 3 Species = fundamental unit of organization in nature (unit of classification and rank) • Ornithologist Ernst Mayr identified 137 birds in Papua New Guinea • Native Papuans already had names for 136 species 4 Species Concepts • Morphological : defines a species by structural features (different species look different from each other) • Paleontological : focuses on morphologically discrete species known only from the fossil record • Ecological : (habitat) 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 (e.g. all dogs, all pigeons, etc)
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5 Biological species concept is most popular, but does not work in all situations • Fossils • Asexual taxa • Taxa not amenable to breeding studies 6 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…. 7 Two types of reproductive barriers • I) Prezygotic • II) Postzygotic 8 •P re zygotic barriers impede mating or hinder fertilization if mating does occur: 1. Habitat isolation ( wrong place ) 2. Temporal isolation ( wrong time ) 3. Behavioral isolation ( no attraction ) 4. Mechanical isolation ( can’t copulate/pollinate ) 5. Gametic isolation ( can’t fertilize
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This note was uploaded on 10/03/2009 for the course BISC 120 at USC.

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Lecture 7 - Chapter 24, Sections 1 and 2 - Speciation - Two...

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