presentation_10 - Lecture 10 Patterns of diversity Counts...

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1 Lecture 10 Patterns of diversity Counts of taxa in the fossil record Geological period or stage Solid lines represent presence of taxa in the fossil record. Dotted lines represent intervals in which taxa are inferred to have been present (although fossils are absent) because the taxa appear later [either in the fossil record or as living organisms (red dots)]. a bc de f
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2 Counts of taxa in the fossil record Geological period or stage a bc de f Are counts an accurate reflection of actual diversity? Bias introduced because geological periods or stages vary in duration, and more recent periods are represented by greater volumes of exposed sediments. If counts of living species are included, then danger that pattern will reflect “pull of the recent.” Patterns of diversity for marine animal families during the Phanerozoic
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3 How does diversity (N) change over time? r : rate of diversity change per unit time: r = S - E S : rate of origination per unit time E : rate of extinction per unit time Is r, S or E constant or do they depend on current diversity? Rate of change in taxonomic diversity: balance between origination and extinction Exponential growth: rate of change in diversity, r, is independent of current diversity (diversity independent). r = S - E, S & E are constant Logistic growth: rate of change in diversity depends on current diversity (diversity dependent). r = r 0 (N max - N)/N max depends on current diversity. N max = maximum diversity that can be supported by the environment.
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This note was uploaded on 09/28/2008 for the course BIOEE 2780 taught by Professor Geber during the Fall '07 term at Cornell University (Engineering School).

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presentation_10 - Lecture 10 Patterns of diversity Counts...

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