"Michael Ragland"  wrote in message
news:c85hgg$2gfn$1{at}darwin.ediacara.org...
>
> On Fri, 14 May 2004 05:13:34 +0000 (UTC),
ragland37{at}webtv.net (Michael
> Ragland) wrote:
> Species- One kind of organism. Of sexually reproducing
organisms, one or
> more natural populations in which individuals are
interbreeding and are
> reproductively isolated from other groups.
> Is this a sufficient definition of species? I've been
reading some of
> the controversy over this term and as far as I can see
this is an apt
> definition of biological species. It doesn't take anybody
with a little
> general knowledge of Darwinism and embryology that we were
once
> "different" species. Over a long gradual period of time we
evolved from
> other life forms or "species". If one sticks to our
current definition
> of species I think there is no contadiction with
evolution. However,
> strictly in terms of evolution the term "species" is fluid
and ever
> changing.

Indeed! But even in the reproductive approach (i.e.,
different
species are those "kinds" which cannot interbreed) there is
fundamental ambiguity, no. This is imposing a discrete or
qualitative boundry between species where such boundry is,
of necessity, continuous (flexible) and quantitative. How
did the first organism of any new species come to be?
Presumably, one parent's biochemistry was enough alike to
the child's such as to preclude there being a fatal antibody
reaction (or some comparable example for other functioning
or morphology.) Where then is the necessary-similarity-line
to be drawn? How can it be definite and non-variable. This
question is hard for me to understand.

>There is no question, assuming we don't destroy ourselves,
> that in a billion years we won't resemble anything like
what we do now
> in terms of internal and external morphology.
Nevertheless, as
> incredible as it may seem there will likely be vestiges of
us remaining
> a billion years from now...to use an analogy like the
human embryo at a
> certain early stage briefly resembles or is like a fish.
> There is no question evolution can be externally
influenced by future
> genetic engineering and this in itself will be a new form
of evolution.
> Natural selection won't be controlled but will be
gradually influenced
> and at some point in the far off future replaced
completely by
> artificial selection via genetic engineering.

Without question, correct! I have ranted here many times
about genengineering to be the next stage of "natural"
evolution. It may not be that far off either.

> Does everybody agree with the aforementioned definition of
species? Do
> people agree on an evolutionary scale the term and meaning
is fluid and
> subject to change?

Sounds right to me, but I am a chemist and only play
biologist here. Will take a look at the references you cite
below to try to
learn more 'bout this stuff.   :)
.....tonyC

> There are many definitions of "species", useful to
different categories
> of biologist under different circumstances. The
"biological species"
> definition you give above is usually attributed to E. Mayr
and is
> particularly useful for understanding the processes of
evolution (the
> reason why this particular definition was created).
However it really
> isn't at all practical for field work, where the
"morphological species"
> is usually used. There are ecological species,
phylogenetic or
> "Hennigian" species, etc. Look at the book edited by
Wheeler and Meier,
> "Species Concepts and Phylogenetic Theory: A Debate"
>
http://www.columbia.edu/cu/cup/catalog/data/023110/0231101422.HTM
>
>
> Biology has a tricky way of generating weird organisms
that defy all our
> clever ways of sorting and categorizing and explaining
them. No matter
> what basic "rule" or"law" you invent in biology, somewhere
there will be
> a living thing that violates your rule or spans your
categories.
>
> RAGLAND:
> How coiuld it be any other way:)
>
>
>
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