Hi Conch-friends,
Dear Gijs, you can see more information in "The five Kingdoms", writed by
Lyn Margulis, 1988.
On Mon, 30 Mar 1998, Robert Avent wrote:
> Hello Gijs,
>
> I'm not really sure as to the placement of some of the unicellular
> forms, including the flagellates, or the reasons for lumping and
> splitting at some level. When I was in school (late pleistocene) it
> was really a bummer that some flagellates, e.g. Euglena, had
> chloroplasts like plants. There are those that would erect a phylum
> for the Euglenophyta, and there are probably lots of schemes among the
> experts. The important thing to remember is that the structure and
> function of all of the lower algae (e.g. diatoms and dinoflagellates)
> are pretty well understood, even if the evolutionary relationships
> might be in question. At these levels, there are certain very basic
> determinators, largely structural, biochemical, and physiological,
> that separate the groups.
>
> The viruses are just that: viruses -- organized bundles of proteins
> and nucleic acids, mainly, that replicate intracellularly (within
> another's animal or plant cells) and depend on the host cell to
> perform many necessary biochemical functions. Not an animal!
>
> My original point was that even at the highest levels of organization
> (forget genus and species) there have been controveries and there were
> will be more. What bemuses me is that some amateur "biologists" are
> wont to discuss the minutae of binomial nomenclature and such things
> without a feel for the bigger picture and the biological principles
> that unite all critters. Taxonomy is important and necessary, but it
> becomes a lot more fun within the greater realm of science.
>
> Yes, there are two fundamental embryological types resulting in
> different body plans in the higher animals -- the protostomes and
> deuterostomes. They have different cell cleavage patterns (spiral and
> radial), and different ways that that they form the various germ
> layers in the older embryo which later become the various organs.
> Chordates and echinoderms are deuterostomes. Molluscs and arthropods
> are protostomes.
>
> Thanks for the questions.
>
> Any good recent college biology text will give you a lot more of the
> details.
>
> Bob Avent
> Minerals Management Service
>
>
> ______________________________ Reply Separator _________________________________
> Subject: Bacteria
> Author: "Gijs C. Kronenberg" <[log in to unmask]> at ~smtp
> Date: 3/27/98 1:56 PM
>
>
> Dear Dr. Avent,
>
> Thanks for this info; apparantly I back some years with my knowledge. It
> also appears that some unicellular groups are now placed more
> satisfactoraly (e.g. flagellates). I recall that theyonce were in a group
> which was best defined as: non animal, non plant and not fungi. Am I still
> correct in believing that virusses are not classified as living organisms?
> The part down from Kingdom I already knew..... (no alterations as far as I
> can see)
> Yet there might be a splitting up in the Kingdom Animalia, as there appears
> (as far as I can remember) a fundamental difference after the third or
> fourth cell division (is this the correct American way of expressing) after
> fertilization. This would for instance imply that we are more related to
> sea urchins that to molluscs.
>
> Gijs C. Kronenberg
>
David Maceira F.
Malacology. BIOECO.
Centro Oriental de Ecosistemas y Biodiversidad.BIOECO.
Museo de Historia Natural "Tomas Romay".
Enramadas # 601 esq. Barnada.
Santiago de Cuba. 90100.
Cuba.
E-mail: [log in to unmask]
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