PDF_notes_speciation

PDF_notes_speciation - Outline Thur Jan 31 What are species...

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1 Thur Jan. 31: Species and S peciation Outline • What are species? What are species? • How do new species arise? How do new species arise? For dessert: random amusing factoids For dessert: random amusing factoids Definitions • Species = “kind” • Speciation – the process by which one species splits into two What are species? What are species?
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2 How best to recognize biological species? • Morphology or appearance is simple and obvious, but has important drawbacks. • For most purposes, biologists rely on a different criterion: reproductive isolation in nature (ability to interbreed). Two Species concepts • Morphological (Linnaeus, etc) • Biological (Ernst Mayr) – “Species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.” How do new species arise? How do new species arise? Types of Evolutionary change: • Anagenesis – Change of a single lineage over time • Cladogenesis (speciation) – The splitting of one lineage into two distinct lineages Repeated cladogenesis leads to phylogenies or “family trees”
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3 All living things are part of a single phylogeny or “family tree” Figure 24.3 Speciation May Be a Gradual Process Mechanisms of speciation: relevant Greek roots : patris = “country”, or place sym = “with” allo = “different” para = “beside” Allopatric speciation • Speciation requires genetic isolation • In allopatric speciation this results from complete geographic separation. – a.k.a. ‘geographic speciation’
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PDF_notes_speciation - Outline Thur Jan 31 What are species...

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