Lecture 10 - MICROEVOLUTION PATTERNS OF DIVERSITY Changes in taxonomic diversity over evolutionary history o Methods for estimating changes in

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MICROEVOLUTION: PATTERNS OF DIVERSITY Changes in taxonomic diversity over evolutionary history o Methods for estimating changes in diversity Count number of taxa in fossil record (taxa distinguished by morphology) Count each geological “stage” in geological record Do we count species, genera, or families? Use the genera or families because the species record is so specific it is very spotty/incomplete Are counts an accurate reflection of actual diversity? Stages vary in duration, may not be recorded Volume of exposed sediments differ because the further back in time we go, the fewer undestroyed rocks still exist “pull of the recent” Biases Some taxa don’t fossilize well If we look at geological periods, they are different lengths so will vary in diversity The further back in time we go, the fewer undestroyed rocks still exist FIGURE BELOW: Look at drops and plateaus Marine fossil record (terrestrial may be different) Evidence for increasing diversity (positive slope), episodic mass extinctions (sudden drops), and density dependent diversity (plateaus)
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o Modeling changes in diversity “S” – Origination rate “E” – extinction rate “r” – rate of diversity change per unit time Exponential – UNLIKELY – rate of change of diversity is independent of current diversity – S (rate of origination) and E (rate
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This note was uploaded on 03/31/2008 for the course BIOEE 2780 taught by Professor Geber during the Fall '07 term at Cornell University (Engineering School).

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Lecture 10 - MICROEVOLUTION PATTERNS OF DIVERSITY Changes in taxonomic diversity over evolutionary history o Methods for estimating changes in

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