Potential problems when

Potential problems when - turnover of taxa without...

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Potential problems when taxonomy is based on morphology : high rate of morphological evolution may lead to the division of organisms into many chronospecies . This can result in a high rate of taxonomic evolution: with pseudoextinction and pseudoorignination, taxonomic rates of evolution can be correlated with morphological rates of evolution (graph A). But , the reverse (morphological rates correlated with taxonomic rates) will not necessarily hold in cases where real extinction of taxa, and replacement by newly evolved taxa, occurs at a high rate. The latter does not assume there is continuous change specific morphologies, thus we could have high rates of
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Unformatted text preview: turnover of taxa without extensive morphological change (graph B). The relationship between morphological and taxonomic rates also depends on which characters are used to determine taxonomic status . One character may evolve rapidly in a lineage but the lineage may not be split into chrono "genera" because "important" characters have not changed, i.e., there can be mosaic evolution . Haldane proposed a unit of measure: 1 darwin = change by a factor of e per million years (e = base of natural logs = 2.71828). See page 553 and figure 20.1, pg.554. Horse teeth : 0.04 darwins = 4% per million years Triceratops lineage of dinosaurs: 0.06 darwins...
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