Trees C - 10/20/09 Overview I. What is a phylogeny? II....

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10/20/09 1 Overview I. What is a phylogeny? II. History III. How do we read trees? IV. How do we build trees? A. characters B. reasons for similarities 1. homology 2. homoplasy 3. shared & derived homologies C. tree building techniques 1. outgroup comparisons 2. parsimony V. Why are phylogenies useful? VI. Molecular clocks Which characters are shared, derived homologies? How do you find out? D. Tree building techniques 1. Outgroup comparisons 2. Parsimony Outgroup comparisons Ingroup – a group of taxa that are of interest, assumed to be monophyletic Outgroup – one or more taxa assumed to be phylogenetically outside the ingroup, although related Example – lizards - outgroup to dinosaurs, crocodiles, birds Outgroup comparisons can distinguish between ancestral and derived character states Outgroup comparisons amniotes - animals that have an egg membrane, amnion, during development Outgroup comparisons Imagine amniotes: mouse, kangaroo, eagle, crocodile, tortoise, robin Mouse and kangaroo –viviparous Others - oviparous Vivipary & ovipary - which is ancestral, derived? Use outgroup
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10/20/09 2 Outgroup – frogs/salamanders Outgroup breeds oviparously - ancestral state Assume state a is ancestral because of outgroup D. Tree building techniques 1. Outgroup comparisons 2. Parsimony – principle for developing phylogenies Old concept (1300s) assumes that the simplest explanation is most likely to be correct
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This note was uploaded on 12/02/2009 for the course BILD BILD 3 taught by Professor Woodruff during the Fall '08 term at UCSD.

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Trees C - 10/20/09 Overview I. What is a phylogeny? II....

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