Some consequences

Some consequences - a higher speciation rate among...

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Some consequences: 1) species selection can introduce evolutionary trends and 2) differences in morphological or taxonomic rates of evolution among different lineages can be due to species selection. The important point is that it is the pattern of speciation that drives such trends, not the direction of morphological changes. An excellent example of the dynamics of species selection (or how one might interpret data from the fossil record in light of differences in extinction and speciation rates) is provided by Hansen's studies of planktotrophic vs. non-planktotrophic gastropod (snails). Planktotrophic lineages last longer in the fossil record (lower extinction rate) See fig. 23.3, page 643. However, the proportion of planktotrophs decreases in the fossil record (see figure 23.4, page 645 and note typo in figure caption). How can one account for this apparent paradox? If one invokes
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Unformatted text preview: a higher speciation rate among non-planktotrophs, then this might do it; i.e., species selection might account for the patterns of diversity changes. Read the text for this section (pp. 641-644). A general question about species selection: is it a pattern or a process? Following the parsimony of G. C. Williams, can we explain species selection by differential survival of individuals within populations, and if so is species selection just a by-product of individual selection ., or do higher level processes operate? (thus the hierarchical issue in species selection). If the latter is true, the big question remains: is macroevolution decoupled from microevolution?? (i.e., are population-level processes insufficient to account for evolution above the species level? If you talk to a population geneticist they would say NO! If you talk to a paleontologist some would say OBVIOUSLY!...
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This note was uploaded on 11/06/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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