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Lecture 18

Lecture 18: "Macroevolution"

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Biology 1002B
Tom Haffie

Biology Lecture No. 18: Macroevolution (Wednesday, November 16, 2011) RECALL (Phylogenetic Analysis): -Only synapomorphies are informative (not all similarities are homologies, not all homologies are synapomorphies). -Homoplasy is misleading in that it can create similarity between distantly related groups (convergence) and can erase similarity between closely related groups (divergence). -Most parsimonious tree (fewest evolutionary steps) is usually the best. Phylogenies Help Classify Life: -Many currently-recognized “groups” are not monophyletic and thus “good” groupings. -Monophyletic: The inclusion of all descendants of the group’s most recent common ancestor. -E.g. crocodilians share a closer common ancestor with birds than with lizards. Other Non-monophyletic Groups: -Prokaryotes: Eukaryotes are more related (share a closer common ancestor) with Archaea than with prokaryotes. -Fish: Fish are more related to reptilians than with sharks. -Birds: Birds are more related to crocodilians than with mammals, despite them being endotherms. Patterns In Macroevolution: -The fossil record, the mode and tempo of evolution, and evolutionary trends (such as changes in body size) are all common patterns in macroevolution. Age Of Fossils: -Law of superposition states that whenever a sedimentary rock formation remains undisturbed, the bottom are older than top. -Therefore one reads rock strata from bottom to top and
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