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Re: warm-bloodedness




Timothy Williams wrote

>So we're talking Linnaean hierarchies, yes?  One nice thing about
cladistics
>is that you can dispense with these ranks.  "Mammals, the grades are just
>in, and you achieved an A+ in Morphological Diversity, so you get to have
>your own Class.  Congrats!  Crocs - oh, bad news I'm afraid.  Unfortunately
>that spurt of evolution in the Triassic wasn't quite enough.  You get a D
>for Diversity - I'm afraid you'll have to stay in the Reptilia.  Better
luck
>next time!"

     Cladistics hasn't dispensed with ranks, it still uses genera and
species.  An arbritary decision to divide organisms into units always has to
be made somewehere.  If we could examine every individiual organism that
ever lived, the distinctiveness of individual species, and certainly genera,
would dissappear in a hurry.  It would be clear that divying up species and
genera is really no less arbitrary then higher level divisions like families
and classes.  Fortunately for taxonomy, evolution has conveniently killed
off most of the ancestors and intermediaries between living and extinct
organisms with a patchy fossil record, making what Ken would call "phenetic
gaps" that lets them appear distinct enough to divide.
     Compare two sister taxa on a cladogram, particularly if they are
different genera or species.  Why are they not lumped into the same genus
and species?  Why are ANY of the taxa on the cladogram distinct from one
another?  Why not just lump all the taxa on a cladogram into a single
species?  A decision has been made to keep them seperate on morphological
grounds having nothing to do with common descent.  This is a decision no
less arbitrary or artificial then deciding where to cap off a paraphyletic
group, and like defining paraphyletic groupings, is done for the sake of
convenience.

LN Jeff

You have to study a great deal to know a little.
-Baron de Montesquieu

They may forget what you said, but they will never forget the way you made
them feel.
-Carl W. Buehner
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Jeffrey W. Martz
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