tgamble

"The well developed and firmly established science of taxonomy ironically lends support to Biblical creationism. How so? Consider for a moment the basic proposition of the evolutionary model that life is in a continual state of flux,ever changing through infinitesimally small mutational changes. If this were true, then CLASSIFICATION (caps mine) would be impossible. But, the fact that living organisms are distinctly different and easily classified into seperate categories is in complete harmony with the creation record."

Scott Huse in his book. "The Collapse of Evolution"

I know there are plenty of organisims that are difficult to classify and whatshisname tried to classify life according to kinds didn't he? I'd like to get a few examples of life that is hard to classify (transitional fossils aren't what I'm after. Just life.) Thanks!

PJPSYCO

His premice is flawed in the fact that we classify many species with a level of ambiguity. Depending on how specific you want to go gives you your level of simplisity of classification. the fact that the taxonomical record was in place long before the theory of evolution was even thought up. We find many species that are not as unique as once thought. An example is the baltimore and bullocks oriole who can breed into a hybrid species. Making their taxonomical seperation invalid. As a fact taxonomy in their case is completely controlled by the people who look at them and is therein determined only by their outer characteristics. I think there is also a rodent with the same ideal(though an interesting breeding patern-one can breed with two others, but the others can't breed with each other), but I can't find my reference for it.

Tharmas

As I recall (it’s been a few years since I read it) this is the basic argument that Darwin uses in the first part of The Origin of Species, that in practice it’s often nearly impossible to pin down where one species ends and another begins. He gives example after example.

mac_philo

As Dennett says, "On the Origin of Species" does not really explain species, and indeed, there is no need to. Species are not natural kinds.

johnpatrick

PJPSYCO

Due to the fact you jumped all over me with my misspelling of "satan" elewhere, here is my opp to rip you to bits as you did me. You deserve it, hypocrite.

Premice is really spelled "Premise." Simplisity is really spelled "simplicity." seperation corrected is "separation." I could point out a few more errors that you made but I think you get it now. Don't attack people unless you're sure you are perfect yourself.

lpetrich

However, in many cases, species are well-defined entities, and some evolutionary biologists have risen to the challenge of trying to account for that pattern. The favorite hypothesis is that evolution goes in bursts in small, isolated populations, which then become new species.

In the fossil record, this is manifest as "Punctuated Equilibrium", where species are distinct from each other, the last members of a species had changed relatively little from the first members, and where intermediates are known, but rare.

Consider this <a href="http://www.skeptic.com/01.3.prothero-punc-eq.html" target="_blank">excellent article</a> on the subject. Punctuated equilibrium is much in evidence for complex, sexually-reproducing organisms like many shellfish, but is less apparent in plankton protists like foraminiferans, which reproduce either asexually or alternate sexual and asexual generations. This is because in the former case, big mutations can cause genetic incompatibilities that would not exist in the latter case.

And as to the Bible, its authors only have crude notions of taxonomy; there is no trace of a treelike hierarchy anywhere in the Bible, including its part with the most taxonomic detail: Leviticus 11.

[ March 17, 2002: Message edited by: lpetrich ]</p>

MrDarwin

As a botanist, I could name any number of plants that are difficult to classify, because they either have characteristics of two different (and otherwise well-defined) groups, or because they have some of the characteristics of a group, but not all of them. In most cases, these plants are understood to be early offshoots of a lineage or early in the radiation of a group, which retain archaic features lost by other members of the group, or which split off before certain diagnostic characters originated.

This pattern is pervasive in plant taxonomy and is one reason why cladistics is leading to so much reclassification. Whereas more traditional taxonomists would generally "shoehorn" such organisms into the larger group, overlooking certain inconvenient characters, cladists tend to more tightly define the groups they recognize, and place such organisms into well-defined groups of their own rather than place them with organisms with which they do not share diagnostic characters.

pseudobug

MrDarwin seyz:
[quote]Whereas more traditional taxonomists would generally "shoehorn" such organisms into the larger group, overlooking certain inconvenient characters, cladists tend to more tightly define the groups they recognize, and place such organisms into well-defined groups of their own rather than place them with organisms with which they do not share diagnostic characters.[/link]

That's an interesting way to phrase the difference in approaches to classification schemes, MrDarwin. I just finsihed reading Gould's "Wonderful Life" and that was one of his themes regarding the discovery and treatment of the Burgess Shale fossils.

I think a lot of scientists tend to overlook the slassification strategies/controversies as it doesn't really impact what most do.

Myrmecos

Might just be semantics, but I don't agree. Cladists don't group organisms based on diagnostic characters but on shared, derived characters. For example, cladists do not recognize the Reptilia as a valid group, even though reptiles have a number of diagnostic characters. Many characters indicate that reptiles are a well-defined group. The problem is that the characters that serve so well in diagnosis are pleisiomorphic, not synapomorphic.

Oolon Colluphid

It's probably semantic. Mr D usually knows what he's talking about .

Hey Myrmecos, you're only 4 posts in, and already you're extremely welcome here! Anyone who knows their pleisiomorphic from their synapomorphic is fine by me (I keep reading these words and having to look them up ). Why don't you pop over to the <a href="http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=forum&f=43&SUBMIT=Go" target="_blank">Welcome Forum</a> and introduce yourself?

Cheers, Oolon