Re: Classification: A Definition

[Roberto Takata <rmtakata@gmail.com>]

On 5/9/07, Tim Williams <twilliams_alpha@hotmail.com> wrote:
> For the Monotremata example, Mammalia is a clade inside Synapsida, just as
> Monotremata is a clade inside Mammalia.  Thus, by extension, Monotremata is
> a clade (one of many) inside Synapsida.  The source of confusion for Anthony
> Docimo, as far as I can tell, is that he is assuming that the word
> "monotreme" is supplanted by "synapsid".  This is conceptually incorrect.
>
> As for the example of protists (which also surfaced on this list), the old
> "Protista" is the poster child for just how BAD the Linnaean system was (and
> still is).  Not only did the "Protista" concept vastly understate the huge
> phylogenetic diversity of single-celled eukaryotes, but we even had a
> situation where certain protists were classified as BOTH animals and plants
> (e.g., _Euglena_).  The latter was a product of grouping organisms based on
> "key features" or "gross physical similarities" (as Jerry puts it).
> Euglenids moved and fed like animals, but they also possessed chlorophyll
> like plants, therefore they got put into both Animalia and Plantae.

Well, consider an eukaryote. Maybe it have a bacterian ancestor and an
archaean ancestor. An monotreme is inside Synapsida since Monotremata
is inside Mammalia and Mammalia is inside Synapsida - by transition
Monotremata is inside Synapsida.

So far, so good. But in the cenario above, an eukaryote is inside
Bacteria *and* inside Archaea.It will be BOTH bacteria and archaea.

The utility of a classification system will depend upon what we will
do with it. For Fisheries Department, it will be more useful to
classify an tuna, an crab and a whale as a fish. To the Natural
Resources Conservation Department maybe not.

[]s,

Roberto Takata