3.17.06 L65 - branching pattern throughout the tree •...

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March 17, 2006 Lecture 65: Phylogenetic Trees and Phylogeny Synaptomorphy – Shared Derived Character Parsimony – The principle of simplicity. (simplest way to get there) a.k.a. Occam’s Razor, KISS  principle (Keep It Simple Stupid) Ingroup  – Taxa of primary interest Outgroup  – Taxa that lie outside the group of interest and are the sister taxon to the ingroup.  Homoplasy  – Similarity due to independent evolutionary change (often mistaken for homology) Reconstructing Relationships Use shared-derived characters (synaptomorphies)   family tree of taxa Taxa sharing a derived character state are more closely related to each other that to  taxa  that have the ancestral character state.  Shared-derived characters at different levels in the tree can help us reconstruct the 
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Unformatted text preview: branching pattern throughout the tree • Remember: Any given Tress is considered to be a Hypothesis. Identifying Synaptomorphies • Synapomorphies help us reconstruct evolutionary relationships. Synapomorphies v. homoplasies: Two major ways of differentiating • Choose characters that appear to be homologies • Use many characters for phylogenies—reduce effect of a few homoplasies. Method of Phylogenetic Recostruction: • The Hypothetic creatures of Llenoc • Create character matrix • 4 changes • Construct the most Parsimonius Tree • Parsimonies usually accepted. What characters can be used to constryuct phylogeies? • morphological • molecular • behavioral Use of Phylogentics • Overlay, for example •...
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