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Re: going offlist on Protista, bacteria
Ken Kinman wrote:
Probably best to go offlist to continue these somewhat offtopic
Perhaps a little off-topic, but since it relates to the last 4 billion years
of evolution, of which dinosaurs played an important part for 150 million
years, I?ll beg the indulgence of Dinolist Central. Also, your comments
concern some fundamental aspects of taxonomy and phylogeny, one of which is
central to dinosaur classification.
However, I think it is grossly unfair (and inaccurate) to >characterize
dinosaurs (and all the rest of the metazoans) as occupying a tiny twig >on
the tree of life. Such exaggeration will only confuse and >intimidate
students and everyone else.
Or enlighten them as to the wondrous diversity of unicellular, microbial
life. This isn?t taking anything away from the success of us multicellular
life-forms, just putting our success into perpective. We are just one
corner of the huge domain of Eucarya. And the Eucarya is just one of three
domains of life on Earth.
The number of Metazoan phyla has also gotten out of hand (I >recognized
24, and even that is too many).
?Phyla schmyla?, as I once saw written on a T-shirt. A lot of your
irritation over what constitutes a phylum is resolved if you just abandon
them altogether. A taxon?s position on the tree is all that really counts.
Order Tullimonstrida (Tully monsters) is probably just an aberrant group
of sipunculans or molluscs.
Then it?s probably just an aberrant group within the Sipuncula or Mollusca.
Why agonize over whether the Tullimonstrida should be ranked as a phylum or
class or order. The same problem surrounds whether the black-smoker-loving
Vestimentifera are just unusual pogonophorans, or whether the parasitic
Pentastomida (tongue-worms) are just highly specialized crustaceans. Should
they be granted their own phylum? Who cares? It?s their phylogenetic
position that?s important, so why bother weighing up whether these bizarre
groups are ?different enough? from their ancestors to qualify as a new
phylum. (I?m reminded of Tom?s example of the wayward daughter who comes
home one day sporting pink hair. ?She?ll never be part of our family again?
rants the father. ?No,? says the mother. ?No matter what she looks like,
as our daughter she?ll always be part of our family.?)
Again, you seem to be your own worst enemy Ken. Your concern over the
delineation of the Class Aves from the rest of the dinosaurs is rooted in
the same preoccupation over whether certain groups deserve to be promoted to
higher ranks - whether it be Class, Phylum or Kingdom.
I?m sorry to harp on this, but it concerns a very fundamental aspect of
evolution. One thing I?ve come across when discussing evolution with other
people is the misguided notion that the past 3-4 billion years of evolution
can be interpreted as a march of progress. Vertebrates are not superior to
flatworms, any more than flatworms are superior to sponges, or any metazoan
life form is superior to any bacterium. Each branch on the Tree of Life
just does things differently.
Ken, I?m not accusing you of you of subscribing to this view of evolution,
but your ?Kinmanian? classification perpetuates this myth ? like the
Linnaean hierarchial system which it draws upon. Birds are not superior to
dinosaurs, so why give them a ?Class? of their own. Go way back to the base
of the Aves, and the differences between birds and dinosaurs resolves into
one or two evolutionary innovations. There?s nothing so different between
_Archaeopteryx_ and (say) _Sinornithosaurus_ that one deserves to be raised
into a ?higher? class than the other.
And finally, ether-linked lipids are not restricted to the so-called
"Archaea" (also called Metabacteria, which is an older and more appropriate
I disagree. Completely. The Archaea are fundamentally different to
Bacteria in their genetic machinery and more similar in this respect to
eukaryotes (animals, plants, fungi, ?protists?).
Timothy J. Williams
Iowa State University
Ames IA 50014
Phone: 515 294 9233
Fax: 515 294 3163
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