MrDarwin

Yes, it's just semantics.

One example would be Archeopteryx (as well as pretty much all the earliest birds). Biologists have long classified it as a bird, because there were only two choices: reptile or bird. This despite the fact that it lacks many of the (derived) characteristics of the bird "crown group". But classifying it as a bird because it has wings and feathers--and the creationists have picked up on this over and over, saying it's "just a bird"--overlooks the fact that it doesn't really fit nicely into either group. Certainly, how the groups "reptile" and "bird" are defined is part of the problem, because "reptile" is not a natural group--so whether we classify Archaeopteryx as a bird or a reptile really is just a matter of semantics.

These kinds of problematic organisms are more prevalent than most non-biologists realize, even among living taxa. Trying to fit extinct, fossil organisms into existing classifications just exacerbates the problem.

(Edited to add that for the benefit of the non-scientists here I generally try to avoid jargon in these discussions--it can be a barrier to meaningful discussion.)

[ March 18, 2002: Message edited by: MrDarwin ]</p>

Dr.GH

Huse seems to make several logical errors that haven’t been commented on yet. First, in
addition to “... life is in a continual state of flux ...” it is known that there are long
episodes of stasis, and that not all species, or (more significantly) subpopulations of
species undergo change at the same rates. There may be “... infinitesimally small
mutational changes.” but these are not realized in standard classification unless they have
accumulated, or resulted in an observable morphological or behavioral change in a
population. (This is not a theoretical problem for molecular phylogenics.) Further, while
the rate of species change may be fast on a geological time scale, it is slow compared to
the time required to classify organisms into groups like species. Huse is either ignorant,
psychotic, misquoted, or he is a liar.

MrDarwin

I would guess ignorant. The fact that he would say something like "the fact that living organisms are distinctly different and easily classified into seperate categories" indicates that he is blissfully unfamiliar with the taxonomic literature or the debates that rage therein.

lpetrich

Cladistics has a rather intimidating jargon; I'll "translate" the two terms toward the end of Myrmecos's post:

Plesiomorphic -- shared ancestral
Synapomorphic -- shared derived

Compare reptiles vs. birds and mammals. Reptiles have several features in common, but they are all ancestral features; the other two have various derived features (feathers or hair instead of scales covering their bodies, to list a trivial example). The cladistically-appropriate approach would be to define a group Amniota that includes all three, and then to break up Reptilia into subgroups comparable to Aves or Mammalia. The name Amniota is on account of amniote eggs, a shared derived feature relative to other vertebrates.

bluefugue

Bifurcation fallacy. Why particularly "Biblical" creationism? Why not the Vedic variety, or any other?

Peez

Or, for that matter, some other mechanism of evolution. Lamark is best known for the inheritance of acquired characteristics, but he also proposed a mechanism of evolution without common descent.

Peez

Quetzal

Some of my favorites include the colonial animals like Physalia physalis, or Portuguese Man-o-War (four different animals symbiotically bound - the float (pneumatophore) is a single individual and supports the rest of the colony, the tentacles (dactylozooids) are polyps concerned with the detection and capture of food and convey their prey to the digestive polyps (gastrozooids), and reproduction is carried out by the gonozooids, another type of polyp.) This beastie is classified as a cnidarian - although I think it's stretching things a bit. Since the basic composants are polyps (cnidaria), that's why it's classified that way. However, none of them can live without the others, hence it's really an organism in its own right. Cnidaria? Hmmm, maybe, maybe not.

Another is Mixotricha paradoxa, a bacterial colony consisting of five different kinds of symbiotically linked bacteria in a single membrane. Bacteria? Proto-eukaryote? Other?

Then there's always lichens - symbiotic fungi/blue-green algae. Plant? Animal? Fungus? D none of the above?

I wonder what "kind" these critters belong to?

Ergaster

That reminds me of this paragraph from a review of "Tornado in a Junkyard" by James Perloff:

I durned near wet myself laughing when I read that last sentence....

Just ask any paleontologist about how "obvious" the differences between species are, especially in stem organisms.

Deb

lpetrich

It's essentially a colony of jellyfish that acts like a single super-jellyfish, which causes some confusion as to whether it is worthy of the label "jellyfish".