Punctuated Equilibri1

Punctuated Equilibri1 - Punctuated Equilibria PE vs....

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Punctuated Equilibria PE vs. Phyletic Gradualism Punctuated Equilibria could have been advanced simply upon the basis of features of geology, taphonomy, geography, and taxonomy. However, that is not how Eldredge and Gould chose to do it. Instead, they codified what they saw as an inaccurate and incorrect "picture" of the fossil record, labelled it as "phyletic gradualism", and demonstrated that their PE was to be preferred on several points. The essential features of "phyletic gradualism" are described by Eldredge and Gould. In this Darwinian perspective, paleontology formulated its picture for the origin of new taxa. This picture, though rarely articulated, is familiar to all of us. We refer lo it here as "phyletic gradualism" and identify the following as its tenets: 1. New species arise by the transformation of an ancestral population into its modified descendants. 2. The transformation is even and slow. 3. The transformation involves large numbers, usually the entire ancestral population. 4. The transformation occurs over all or a large part of the ancestral species' geographic range. These statements imply several consequences, two of which seem especially important to paleontologists: 1. Ideally, the fossil record for the origin of a new species should consist of a long sequence of continuous, insensibly graded intermediate forms linking ancestor and descendant. 2. Morphological breaks in a postulated phyletic sequence are due to imperfections in the geological record. [ ] While it is nice to have terminology by which obtuse opponents of a theory may be conveniently labelled, there is no actual point to even bringing up "phyletic gradualism" in establishing PE. Eldredge and Gould quoted from Darwin in their 1972 paper to establish their concept of
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This note was uploaded on 11/14/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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Punctuated Equilibri1 - Punctuated Equilibria PE vs....

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