>Pray, what is a species?
>
>This is a very serious question.
There are several different definitions. The standard biological species
definition is "a population of interbreeding individuals that is
reproductively isolated from other such populations under natural
conditions." This provides a good theoretical definition but is often
difficult to apply in real situation in the field and is obviously not
applicable to the fossil record.
In practice what is commonly used is a morphological definition. In this
case, anatomical variation within a species is less than that between
species. Maintaining anatomical distinctions between coexisting
populations (or those in direct contact) would seem to require a degree of
genetic isolation sufficient to prevent the mixing of gene pools (ie they
are reproductively isolated). the existence of populations (or fossil
collections) with statistically distinct anatomies is thus considered a
basis for species designation.
There are now also those who advocate using genetic divergence as a
criteria for recognizing species.
Keith
Keith B. Miller
Department of Geology
Kansas State University
Manhattan, KS 66506
kbmill@ksu.edu
http://www-personal.ksu.edu/~kbmill/
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