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.
 
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