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bio lecture 6 - Homoplasic traits B Homoplasies can create...

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Lecture Outline 6 – Phylogeny and Systematics II I. Terms A. Synapomorphy - shared derived traits B. Plesiomorphy - shared ancestral traits C. Autapomorphy - derived but not shared II. Steps to building a phylogeny A. Choose an outgroup (distantly related group used as a reference to help infer evolutionary history within a more closely related group) B. Identify synapomorphies C. Collect data D. Create phylogeny * REMEMBER: Synapomorphy and plesiomorphy are relative terms II. Types of Phylogenetic trees Fig 26.12 A. Cladograms – branch length arbitrary, basic grouping B. Phylogram – branch length indicates number of differences C. Ultrametric – branch length indicates time since divergence, Has a time line at the bottom III. The rule of parsimony A. Hypothesis requiring least number of evolutionary “events” is likely correct 1. based on Occam's Razor (simplest solution is the best) B. The best phylogenetic hypothesis is the most parsimonious hypothesis IV. Homology versus Analogy A. Analogous traits are also known as
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Unformatted text preview: Homoplasic traits B. Homoplasies can create misleading phylogenies V. Phylogenetic groups A. Monophyletic – group consisting of ancestor and ALL descendants (i.e. a clade) a clade is at each node B. Paraphyletic – group consisting of ancestor and MOST descendants, missing some descendants because some might have gone extinct VI. Molecular Clocks A. Technique used to relate molecular differences between two lineages to their absolute time since divergence B. Assumes constant mutation rate VI. Modern use of Phylogenies A. Reveal changes not captured by the fossil record-helps us understand how things evolved over time (i.e. brains can’t are hard to be fossilized because it is soft tissue B. Resolve evolutionary hypotheses (i.e. what came first lung or swim bladders) C. Identify illegal activity Lecture Outline 6 – Phylogeny and Systematics II D. Track the origins and spread of infectious disease 1. HIV 2. Bird flu 3. West Nile Virus...
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