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Re: Taxonomy (long)



In a message dated 95-12-15 14:24:34 EST, cpretzma@magnus.acs.ohio-state.edu
(Chip Pretzman) writes:

>The more objective we can get, the better off we may be. Nature may present
>apparent continuums, but somewhere in the genome are differences that can be
>used to separate two organisms right down to the individual level, or right
>up to a whole life level, past the three kingdoms(clades of life) on the
>earth, and everywhere in between. There are gene sequences that never
>change, at least in the three or so billion years so far life has existed,
>and there are genes that change by the day in certain organisms.


Thanks for your very interesting post!

Nature does indeed present us with guidelines between taxa: they're called
evolutionary novelties. An organism or fossil that exhibits a key
evolutionary novelty--whatever its nature--surely may be placed in a
different taxon--whatever _its_ nature--from a similar orgnism or fossil that
doesn't. These guidelines, however, seem to have been discarded, or at least
greatly minimized, by the cladists these days, who prefer to use branching
events because of their obsession with phylogeny.

A taxonomist classifies organisms by their appearance (in the broadest sense
of the term, including, for example, the "appearance" of the genome), not by
their descent, which can only be inferred secondarily from appearance.