BIOL 101 1nd Edition Lecture 24 Outline of Last Lecture I Reproductive Barriers a Speciation b Hypotheses Outline of Current Lecture I Formation of Reproductive Barriers II Gene Flow III Species Concept IV Allopatric Speciation Current Lecture Two populations must have gene flow blocked with or without a physical barrier once this form of microevolution is blocked natural selection mutation and genetic drift make two different species that eventually cannot interbreed II How do reproductive barriers form When gene flow is blocked between two populations Co speciation hypothesis human head and chimp lice lineages diverged at the same time that hominins and ancestral chimps diverged New niche hypothesis human pubic and head lice lineages diverged because hominins lost their body hair and developed two hair niches 2 A burst of divergences from a single ancestor that leads to many new species each adapted to a new habitat or using new resources adaptive radiation Phylogenetjc studies of lice suggest that hominins acquired a second species of louse 3 4 million years ago does not correlate with humans losing body hair Body louse arose less than 72 000 years ago correlates with clothing These studies are inconclusive Types of Species Concepts These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 1 2 3 4 biological species concept morphological ecological phylogenetic Phylogeny the study of evolutionary relationships B Allopatric Speciation when you have a geographic barrier impeding gene flow
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