These models just provide ways of thinking about the history of diversity on earth

These models just provide ways of thinking about the history of diversity on earth

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These models just provide ways of thinking about the history of diversity on earth. What might such diversity dependent forces/phenomena be? Do they exist? What do the data tell us? First, how do we get the data? Simple on one hand: count the number of taxa present in each time interval. Complicating issues: species concept = typological (morphospecies) any "reasonably" different forms will be classified as a different species. If these morphospecies co-occur in time and space then they are probably "good" species and should be counted as separate entities. Many fossil series show temporal gradations of morphology from one form into another. These chronospecies introduce error into estimates of diversity since the end of one name and the beginning of another name look like extinction and origination,
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Unformatted text preview: or pseudoextinction and pseudoorigination . Moreover, the taxononic level under consideration will alter one's estimate of the patterns of diversity since lower taxa (species, genus) might vary in diversity more than higher taxa (family, order). Also, differences in the identification of taxa will alter estimates of patterns (see figure 20.12, pg.577). In the literature it is difficult to tell which extinction/speciation events represent real events and not "chrono" events. We can avoid this problem by tabulating higher taxa . It is unlikely that all representatives of a genus will evolve simultaneously into a new genus, but what is a genus (or a family)? is it a real unit of diversity?...
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