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Author: Robert Karl StonjekRobert Karl Stonjek Date: Apr 11, 2008 10:19
And the first animal on Earth was a...
A new study mapping the evolutionary history of animals indicates that
Earth's first animal--a mysterious creature whose characteristics can only
be inferred from fossils and studies of living animals--was probably
significantly more complex than previously believed.
The study, which was funded by the National Science Foundation (NSF), is the
cover story of the April 10, 2008 issue of Nature. Using new high-powered
technologies for analyzing massive volumes of genetic data, the study
defined the earliest splits at the base of the animal tree of life. The tree
of life is a hierarchical representation of the evolutionary relationships
between species that was introduced by Charles Darwin.
Shaking Up the Tree of Life
Among the study's surprising findings is that the comb jelly split off from
other animals and diverged onto its own evolutionary path before the sponge.
This finding challenges the traditional view of the base of the tree of
life, which honored the lowly sponge as the earliest diverging animal. "This
was a complete shocker," says Dunn. "So shocking that we initially thought
something had gone very wrong."
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Author: LorentzLorentz Date: Apr 12, 2008 11:03
On Apr 11, 1:28 pm, "Robert Karl Stonjek" bigpond.net.au>
wrote:> And the first animal on Earth was a...
>
> A new study mapping the evolutionary history of animals indicates that
> Earth's first animal--a mysterious creature whose characteristics can only
> be inferred from fossils and studies of living animals--was probably
> significantly more complex than previously believed.
>
> The study, which was funded by the National Science Foundation (NSF), is the
> cover story of the April 10, 2008 issue of Nature. Using new high-powered
> technologies for analyzing massive volumes of genetic data, the study
> defined the earliest splits at the base of the animal tree of life. The tree
> of life is a hierarchical representation of the evolutionary relationships
> between species that was introduced by Charles Darwin.
>
> Shaking Up the Tree of Life
>
> Among the study's surprising findings is that the comb jelly split off from
> other animals and diverged onto its own evolutionary path before the sponge. ...
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Author: Paul CiszekPaul Ciszek Date: Apr 13, 2008 14:38
In article darwin.ediacara.org>,
Lorentz yahoo.com> wrote:>>
> The cnidarians have nerve and muscle tissue. The sponges don't
>have either nerve or muscle tissue.
> If this is true, one of three things are true. 1) An ancestor of
>the sponge had nerve cells and muscle tissue. 2) The comb jelly has
>evolved nerve-like tissue and muscle-like tissue independently of the
>jellyfish. 3) The genetic methods failed to find the correct order of
>split off lineages.
If Porifera are considered paraphyletic, what is "left out"? (i.e.,
paraphyletic means that the group contains the last common ancestor of
ite members, but not all the descendents of that ancestor.)
Seems like I read somewhere once that sponges might be polyphyletic,
or might represent a separate attempt at multicellularity than other
animals. Could this have thrown off the genetic tree software?
> I have always suspected that the "tree of life" was really more
>like a "network of life" to some extent.
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Author: LorentzLorentz Date: Apr 14, 2008 10:08
On Apr 13, 5:48 pm, nos...@ nospam.com (Paul Ciszek) wrote: > In article darwin.ediacara.org>,
>
> Lorentz yahoo.com> wrote:
>
>3) The genetic methods failed to find the correct order of>>split off lineages.
> Seems like I read somewhere once that sponges might be polyphyletic,
> or might represent a separate attempt at multicellularity than other
> animals. Could this have thrown off the genetic tree software...
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Author: Aidan KarleyAidan Karley Date: Apr 29, 2008 09:28
In article darwin.ediacara.org>, Lorentz wrote:> One possible source of error they may not have considered is
> hybridization. Maybe they ctenophores didn't branch off. Maybe the
> first ctenophore was a hybrid between a sponge-like creature (no
> nerves) and a cnidarian like creature (with nerves). Or maybe a
> lateral gene transfer added some sponge DNA to a jellyfish.
>
Has "lateral gene transfer" been demonstrated to occur for any
Eukaryotes? Certainly it has for Bacteria and Archaebacteria, but
Eukaryotes ? I'm not so sure.
--
Aidan Karley,
Aberdeen, Scotland
Written at Wed, 16 Apr 2008 08:28 +0100, but posted later.
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0
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Author: John WilkinsJohn Wilkins Date: Apr 30, 2008 10:43
Aidan Karley email.provider.invalid> wrote:
> In article darwin.ediacara.org>, Lorentz wrote:>> One possible source of error they may not have considered is
>> hybridization. Maybe they ctenophores didn't branch off. Maybe the
>> first ctenophore was a hybrid between a sponge-like creature (no
>> nerves) and a cnidarian like creature (with nerves). Or maybe a
>> lateral gene transfer added some sponge DNA to a jellyfish.
>>
> Has "lateral gene transfer" been demonstrated to occur for any
> Eukaryotes? Certainly it has for Bacteria and Archaebacteria, but
> Eukaryotes ? I'm not so sure.
>
A bacterium has been observed conjugating with a hamster cell. If it can
happen once, it can happen often.
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Author: DKDK Date: Apr 30, 2008 10:43
In article darwin.ediacara.org>, Aidan Karley email.provider.invalid> wrote:>In article darwin.ediacara.org>, Lorentz wrote:>> One possible source of error they may not have considered is
>> hybridization. Maybe they ctenophores didn't branch off. Maybe the
>> first ctenophore was a hybrid between a sponge-like creature (no
>> nerves) and a cnidarian like creature (with nerves). Or maybe a
>> lateral gene transfer added some sponge DNA to a jellyfish.
>>
> Has "lateral gene transfer" been demonstrated to occur for any
>Eukaryotes?
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