Bio1b Summer 2008 Eric Harris Evolution Lecture 7 Page 1 of 2 EVOLUTION LECTURE 7 MACROEVOLUTION Reading 7th ed 481 490 8th ed 501 504 525 531 A Patterns of speciation in the fossil record i Phyletic gradualism anagenesis transformation of an unbranched lineage to a different state species ii Cladogenesis branching of new species from a parent species Both Anagenesis and Cladogenesis may occur in the same evolutionary tree iii Punctuated equilibria long periods of stasis punctuated with sudden episodes of speciation B Macroevolutionary mechanisms Origin of evolutionary novelty i Exaptations structures that evolved in one context becomes co opted for another function ii Morphology and development Allometric growth slight changes in relative growth rates can have substantial changes in adult Heterochrony evolutionary changes in the timing or rate of development Paedomorphosis retention of ancestral juvenile structures in a sexually mature adult Hypermorphosis Homeosis alteration in the placement of different body parts iii Species selection differential speciation success Natural selection causes changes in each lineage Species selection causes changes in the numbers of lineages with different properties Updated on 06 17 08 Bio1b Summer 2008 Eric Harris Evolution Lecture 7 Page 2 of 2 C Patterns in the fossil record extinctions and radiations diversification and decimation i Conventional representation cone of increasing diversity e g the Burgess shale ii Adaptive radiations e g origin of shells origin of insect wings iii Mass extinctions Permian extinction extreme vulcanism and formation of Pangaea Cretaceous extinction asteroid hypothesis and or climate change Mass extinctions affect different groups very differently Why do some groups survive Updated on 06 17 08
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