Hi, Peg.
Peg writes:
Mr Jack writes:
There is no single, clearly defined and universally applicable definition of what a species is.
why do you think that is the case?
Just to make it clear, Peg:
Under an evolutionary model, we
expect definitions and categorizations to be unclear and awkward.
Under a "baraminological" model, we should expect definitions and categorizations to be clear and apparent.
Inability to distinctly divide "kinds" indicates that "kinds" are not as distinct as creationists say they are.
For instance:
Peg writes:
so what do we call two types of spider that cannot reproduce, a different species or a different kind?
Entomology (and arachnology) does not separate species by reproduction in most cases, but by morphological characteristics. It's awfully hard to determine whether two specimens might interbreed, especially since we have to kill them to get close enough to see them clearly.
But, as for your example, tarantulas are about 900 described species* of spiders grouped into the family Theraphosidae, and black widows are actually 3 of the 31 species of spider in the family Theridiidae and the genus
Latrodectus, which also includes the redback spider from Australia, with which you are probably familiar.
*When I say a "described species," it means that somebody grouped some specimens together, called the group a "species," and assigned the group a name in the primary literature, and nobody has yet thought it necessary to publically denounce the description.
So, technically, you would call them a family and a subgeneric-assemblage-of-species. But, these are really just arbitrary categories that biologists use to organize and standardize our information, and communicate it with one another: what we call a "family" in entomology does not necessarily correlate with what a mammalogist or ornithologist would call a "family."
This is why, every time somebody makes an argument about "different species" or "it's still a dog," I tell them that it's just a semantic argument: because all they're arguing about is an arbitrary classification of stuff that routinely defies categorization.
Edited by Bluejay, : Added explanation of "described species"
-Bluejay (a.k.a. Mantis, Thylacosmilus)
Darwin loves you.
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