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Lecture 17

Lecture 17: "Phylogeny"

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Biology 1001A
Susanne Kohalmi

Biology Lecture No. 17: Phylogeny th Wednesday, November 9 , 2011 What Is Phylogeny? : -Pattern of evolutionary relationships among organisms. -Phylogeny reconstructs this relationship common among all organisms. Reading Phylogenies: -Living modern species or groups at tips; common ancestors at the nodes. -The rotation or reflection of any node(s) has no effect on the evolutionary timeline of organisms displayed in the phylogeny. Principles Of Phylogenetics: -Evolutionary relationships among organisms reflect how recently (in time) groups of organisms shared a common ancestor. -Phylogenies are constructed using patterns of similarity (the more similar things are the more recently they shared a common ancestor) -Homology: When similarity usually reflects recently shared ancestry. Homology Vs. Homoplasy: -Not all similarity reflects recent common ancestry. Not all similarities are synapomorphies. -Convergence: Misleading similarity despite distant evolutionary relationship. E.g. bug wings, bird wings; whale sonar, bat sonar. -Divergence: Misleading dissimilarity despite close evolutionary relationship. E.g. Darwin’s finches. -Traits that are homologous support true phylogeny, but homoplasious traits will mislead one -What if one cannot distinguish a trait that is hom
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