Phylogeny and Systematics 2

Phylogeny and Systematics 2 - - Monophyletic: Group...

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Phylogeny and Systematics 2 Synapomorphy: shared derived character (new) - Only one useful to make a phylogeny Plesiomorphy: shared ancestral characters (old) Autapomorphy: derived but not shared Steps to Building a Phylogeny - Choose out-group - Out-group: distantly related group (taxon) used as a reference to help infer evolutionary history with a more closely related group - Identify Synapomophies - Collect data on synapomophies - Create phylogeny Three types of Phylogenetic Trees - Cladograms - Branch length arbitrary - Phylograms - Branch length indicates number of differences - The longer the branch, the more number of differences. - Ultrametric - Branch length indicates time since divergence The Rule of Parsimony - Parsimony: The hypothesis requiring least number of evolutionary “events” is likely correct (i.e. Occam’s razor) Parsimony and Homoplasy
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- Parsimony can be misleading due to homoplasy Monophyletic Groups (a.k.a. Clades)
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Unformatted text preview: - Monophyletic: Group consisting of ancestors and all descendants- Paraphyletic: Group consisting of ancestor and most descendants Molecular CLocks- Molecular Clocks: Technique used to relate molecular differences between two lineages to their absolute time since divergence. Assumes constant mutation rate Phylogenies: What are they good for?- They reveal changes not captured in the fossil record- Example: Evolution of brain morphology and tool use- Address Biologically Interesting Hypothesis- Identify Illegal Activity- Transmission of HIV to Humans- Transmission of HIV between Humans- Spread of Bird Flu- Phylogenies and West Nile Virus Summary- Synapomorphy vs. plesiomorphy- Outgroups vs. ingroups- Three main types of phylogenetic trees- The rule of parsimony- Homoplasy can mislead phylogenetic reconstruction- Molecular clocks- The utility of phylogenetic reconstruction-...
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This note was uploaded on 09/21/2011 for the course BSC 2010 taught by Professor Bowes during the Spring '08 term at University of Florida.

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Phylogeny and Systematics 2 - - Monophyletic: Group...

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