Lecture 18 - Lecture 18 Feb 15 Evolutionary Processes...

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1 Lecture 18: Feb. 15 Evolutionary Processes: Natural Selection Evidence for Evolution - fossils & biogeography genetic similarities (homologies) - experiments testing natural selection Modern Synthesis Ways in Which Selection Acts - directional, stabilizing, balancing, and diversifying Regressive Evolution - eye loss in cave populations - ‘simplified’ morphology in parasites Discussion Activity next Week Article on Sexual Selection (week 8 folder) Essay Refs. due today Complete essay due by Feb. 22 Check Qwizdom Points on SAMS https://cats.lsa.umich.edu/ Chapters 24 : 520-523; NAS chapters Biology in the News Evidence that Species Have Changed: Biologists today know much more about the major extinctions that occurred during Earth’s history; we know the Earth is ~ 4.6 billion years old and we have discovered many fossils that show major transitions in different groups of animals over evolutionary timescales. Darwin proposed that the different island species on the Galapagos were similar because they had descended with modification from a common ancestor. Evidence that Species Have Changed: Biogeographic Patterns
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2 Evidence that Species Have Changed: Structural Homologies Structural homology refers to similarity of morphological traits, such as the same general limb structure in vertebrates Structural homologies are a product of descent with modification, i.e., they were inherited from a common ancestor. Evidence that Species Have Changed: Developmental Homologies Developmental homology refers to similarity in embryo morphology and/or pattern of tissue differentiation. For
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This note was uploaded on 12/06/2009 for the course BIO 225 taught by Professor Pavgi during the Spring '08 term at University of Michigan.

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Lecture 18 - Lecture 18 Feb 15 Evolutionary Processes...

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