Re: going offlist on Protista, bacteria

["Tim Williams" <twilliams_alpha@hotmail.com>]

Ken Kinman wrote:


> Probably best to go offlist to continue these somewhat offtopic 
> discussions.

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
name).

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?).


Tim


------------------------------------------------------------

Timothy J. Williams

USDA/ARS Researcher
Agronomy Hall
Iowa State University
Ames IA 50014

Phone: 515 294 9233
Fax:   515 294 3163

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