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Berkeley BIOLOGY 1B - Macroevolution

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John Latto 6/21/07 Evolution lecture 8 - Macroevolution A - Patterns 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 D - 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 replicatorsJohn Latto 6/21/07 Evolution lecture 10 - Evolution and Ecology A - Adding 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’


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Berkeley BIOLOGY 1B - Macroevolution

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