EARTHSC 1122 Lecture 15: EARTHSC Notes 10/7
4 Dec 2015
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Reconstructing evolutionary history: phylogeny: hypothesis of evolutionary history, phylogenetic tree showing ancestor-descendant relationships, cladogram: branching diagram; taxa are grouped on evidence of common ancestry. Constructing a cladogram: start with a list of taxa and character states, assign numeric values to character states, plus = 1 , minus = 0. Primitive state has all zeroes shared character states. Jaws , lungs , etc: find shared derived characters and begin drawing the cladogram, clustering taxa by their, fill in the cladogram by successively adding characters (ex: somewhere along the line write. : includes the ancestor and all its descendants. : lack all descendants; or included forms have multiple ancestries. Patterns of evolution: evolution does not always proceed from simple to more complex (it"s just change, paedomorphesis: early onset of sexual maturity in descendants. Convergent evolution: species can evolve only once but similar structures can evolve more than once in response to similar ecologic pressures (convergence or homoplasy)
