presentation_2 - Homoplasy Similar (homoplasious)...

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Lecture 2 Evidence for Evolution Modification of pre-existing “character” Structures that allow plants to climb (vine) are modifications of leaves (left) or stems (right) See Fig. 3.10
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What is a “character”? Homology Homologous characters
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Homologous structures: Forelimb bones Fig. 3.4 Homologous bones (e.g., R, U) differ in shape Fig. 3.4
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Horse: Fusion of metacarpels Loss of all but 1 toe Vestigial limbs ischium ilium femur Whale Snake pelvis femur Rudimentary hind limbs Termination of hind limbs
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Vestigial genes (pseudogenes) Functional gene Triplet codon Start Stop Start Stop Stop Non-functional pseudogene Intermediate forms Theropod dinosaur Archaeopteryx Sinornis bird Chicken
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Descent with Modification Hierarchical Organization shorter shorter longer shorter longer Homoplasy Homoplasious characters
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Unformatted text preview: Homoplasy Similar (homoplasious) characters in 2 taxa that evolved independently i.e., not directly from an immediate common ancestor Bats wing wing Birds Mammals Lizards Snakes Dinosaurs Crocs Parallel evolution of homoplasious characters: wings in bats & birds Tetrapod limb Parallel evolution of maxillipeds Averoff & Patel 1997 (Fig. 3.7) Convergent evolution Wings in insects vs. birds Function of character (adaptation) vs. ancestral origin of character Stasis Trend Fig. 4.3 Rates & Patterns of Evolution Trilobites conservative 180 tons 5 tons 10 g 100 kg rapidly evolving Adaptive Radiation ~5.2myr Hawaiian Silverswords N. Amer. Hawaiian Silverswords...
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