Evolution lecture 8 Macroevolution APatterns of speciation in the fossil record i Phyletic gradualism anagenesis transformation of an unbranched lineage to a different state species i Cladogenesis branching of new species from a parent species Increases biological diversity Both Anagenesis and Caldogenesis may occur in the same evolutionary tree ii Punctuated equilibria long periods of stasis punctuated with sudden episodes of speciation How sudden is sudden Is this an artifact of the fossil record What causes speciation events B Macroevolutionary mechanisms i Preadaptations 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 Homeosis alteration in the placement of different body parts C Patterns in the fossil record extinctions and radiations diversification and decimation i Conventional representation cone of increasing diversity An example the Burgess shale how to make an arthropod ii Adaptive radiations eg 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 Evolution lecture 9 Systematics and classification Definitions Phylogeny evolutionary history of a species Systematics study of biological diversity in an evolutionary context Taxonomy identification and classification of species A How do we classify organisms Three alternatives i Classical evolutionary systematics uses information on both extent of divergence the branching sequence ii Phenetics makes no evolutionary assumptions and just uses info on measurable similarities differences iii Cladistics only considers branching sequence and not degree of divergence B Cladistics Terminology plesiomorphy shared primitive character synapomorphy shared derived characters i Distinguishing plesiomorphy from synapomorphy using an outgroup ii What cladistics is good for iii Problems with cladistics iv Parsimony or Occam s razor C Modern systematics i New tools DNA comparisons DNA DNA hybridization restriction mapping DNA sequencing Molecular clocks ii Rethinking old relationships Birds mammals and reptiles Pandas and lesser pandas Apes and humans Origin of life i What is life ii Early earth history iii Atmosphere of the early earth iv Survival of the stable v Increasing sophistication of replicators D John Latto 6 21 07 Evolution lecture 10 Evolution and Ecology AAdding evolution to ecological concepts and vice versa i Genetics and behavior Genetics CAN code for behavior but behavior is not ALL genetic ii Evolution and behavior optimal foraging theory iii Genetics and the environment nature vs nurture heritability iv Life history strategies Growth rate number of offspring size of offspring etc v Sex why bother Costs recombination scrambles genotype courtship and mating may be risky finding a mate can be difficult genome is diluted Some possible reasons for the popularity of sex related to the mechanics of DNA repair purges deleterious mutants and thus permits an increased genome size allows a single advantageous mutation to be expressed in homozygote in a patchy environment disruptive effects of recombination may be advantageous B Exam advice i Write your own questions ii Use your textbook iii Look for the point iv Don t overanalyze v Read the question vi Re read ALL the questions answers vii If you have to guess guess intelligently viii Pay attention to negative qualifiers John Latto 6 21 07
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