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Chapter 26

Chapter 26 – Speciation.docx
Chapter 26 – Speciation.docx

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School
McMaster University
Department
Biology
Course
BIOLOGY 1M03
Professor
Jurek Kolasa
Semester
Fall

Description
Chapter 26 – Speciation • Speciation  o A splitting event that creates two or more distinct species fro ma single ancestral  group o An evolutionary independent population or group of populations o Results from genetic isolation and genetic divergence • If gene flow b/w populations stops, mutation, selection and drift begin to act on  populations independently  • The Biological Species Concept: o Critical criterion for identifying species is reproductive isolation o Prezygotic Isolation – prevents individuals of different species from mating o Postzygotic Isolation – offspring’s of matings b/w different species don’t survive  or reproduce o Disadvantage: not applicable to asexual or fossil species  • The Morphospecies Concept: o Identify evolutionarily independent lineages by differences in size, shape, or  other features  o Distinguishing features are most likely to arise if populations are independent  and isolated from gene flow o Disadvantage: features used to distinguish species are subjective • The Phylogenetic Species Concept ( Clade or Lineage): o Consists of an ancestral population, all of its descendants and only those  descendants  o On a tree of populations, each tip is a phylogenetic species o A species is defined as the smallest monophyletic group on a tree that contains  populations • Subspecies  ­ populations that live in discrete geographi
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