Lecture Notes July 1

Lecture Notes July 1 - July 1 2009 Lecture Notes...

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July 1, 2009 Lecture Notes Phylogenies - phylogeny- evolutionary history for a group of organisms - typically as a tree - vertical axis is time Phylogenic Tree - 3 basic components - branches- populations through time - nodes- forks where ancestors splits into 2 or more decedents - tips- extinct or extant (still present) organisms - tip can be rotated around nodes - polytomy- more than 2 groups emerge from a node 1. looks like a starburst 2. can’t distinguish when (and from whom) species evolved from 3. fast radiation of species - sister taxa- groups that occupy adjacent branches linked by a node - tree rooted-bottom node are the most ancient - outgroup- taxon that diverged prior to most ancient node of tree Phylogenetic Groups - monophyletic groups- ancestor and all its descendents - polyphyletic groups – groups of a species with different common ancestor - paraphyletic group- group with common ancestor but only some of its descendents Adaptive Ratiation - appear in phylogenies as polytomies (starbursts) - supports punctuated equilibrium - three potential mechanisms: 4. colonization events habitat unoccupied by competitors in colonized by a species colonizing species quickly radiating to exploit new resources 5. morphological innovation allows new resources to be exploited examples: flowers: dispersed pollen further feathers: theromoregulatory and flight mouth part: feeding options 6. mass extinction remove major competitors allows surviving species to take over previously taken resources Fossils - physical trace of organism that lived in the past - fossil record- collection of all the fossils found
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- fossils give us an idea of the morphology of past organisms and where they lived
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Lecture Notes July 1 - July 1 2009 Lecture Notes...

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