Re: News: The Tree of Life Has Lost a Branch.

In message <tpngp3964117u8urv031e2suif5baic385@xxxxxxx>, Ye Old One <usenet@xxxxxxxxx> writes
The Tree of Life Has Lost a Branch.

http://www.apollon.uio.no/vis/art/2007_4/Artikler/The_Tree_of_Life

Norwegian and Swiss biologists have made a startling discovery about
the relationship between organisms that most people have never heard
of. The Tree of Life must be re-drawn, textbooks need to be changed,
and the discovery may also have significant impact on the development
of medicines.

Tekst: Lars Hoff

The discovery by Norwegian and Swiss researchers has gained attention
from biologists worldwide. The findings come from the largest ever
genetic comparison of higher life forms on the planet. Of 5000 genes
examined, researchers identified 123 common genes from all known
groups of organisms; these common genes have been studied more
closely. The study has required long hours of work from the
researchers and an enormous amount of computing resources—supplied
through a large network of computers at the University of Oslo.

Lost a Branch

“The results were pretty astounding. All non-bacterial life on
Earth—called eukaryotic life— can now be divided into four main groups
instead of the five groups that we have been working with up to now,”
says Kamran Shalchian-Tabrizi, an associate professor from the
University of Oslo’s Department of Biology who has also worked with
the Department of Zoology and Animal Biology and the Department of
Genetic Medicine and Development, at the University of Geneva,
Switzerland.

The Tree of Life (see illustration) has, through the discovery that
the two formerly separated branches share a similar evolutionary
history, lost one of its branches, and this will both improve and
simplify quite a bit of scientific work in the future.

Important Discovery

“Kinship says a lot about shared traits. Our findings can be important
in many fields, such as in the study of the development of life and in
the manufacture of new medicines” says Shalchian-Tabrizi in an
interview with the University of Oslo’s research magazine Apollon.

“Our knowledge of organisms and the development of medicines are often
based on comparative studies across species. It is, therefore,
essential that we know the relationships between the largest groups in
the great diversity of eukaryotes,” he adds.

The research group has, for example, found that brown algae and silica
algae, and groups of single cell organisms like the malaria parasite,
marine foraminifera, and the green sun animalcule (acanthocystis
turfacea) actually belong to the same group. Previously, these species
were thought to be completely unrelated.

“The work that we published in the August edition of PLoS ONE (a
leading open access journal found on the internet) means that the
description of the Tree of Life must be revised in new textbooks,”
says Professor Kjetill S. Jakobsen from the University of Oslo’s
Centre for Ecological and Evolutionary Synthesis (CEES). He is also a
member of the Microbial Evolution Research Group (MERG), led by
Shalchian-Tabrizi, at the Department of Biology. MERG is one of 16
groups that the Faculty of Mathematics and Natural Sciences believes
may have the potential to develop into new Centres of Excellence.

The New Branch

All life on Earth can be divided into two essentially different life
forms—eukaryotes and prokaryotes. The eukaryotes gather their genetic
material in a nucleus, while the prokaryotes (bacteria and archaea)
have their genetic material floating freely in the cell. Eukaryotic
organisms—such as humans—can, as a result of the new findings, be
divided into the following four categories:

• Plants (green and red algae, and plants)

• Opisthokonts (amoebas, fungi, and all animals—including humans)

Opisthokonta consists of animals, fungi and some smaller groups - mesomycetozoans (aka ichthyosporeans aka DRIPS), choanoflagellates and ministeriiid, capsasporid and nucleariid amoebas. Amoeba is not a phylogenetic grouping, but I suspect here that what is referred to is Amoebozoa, which contains slime moulds and some free living amoeba.

Some people believe that the eukaryote root lies between opisthokonts and amoebozoans (collecting unikonts) on the one hand, and all other eukaryotes (collectively bikonts), so it's not indefensible to collapse those two groups into one.

• Excavates (free-living organisms and parasites)

• SAR (the new main group, an abbreviation of Stramenophiles,
Alveolates, and Rhizaria, the names of some of its members)

“The SAR group has to some extent been identified earlier, but we
could not know if it was a correct observation because we lacked
statistical data. To get that data, we first had to reconstruct the
entire eukaryote tree with the help of these 123 genes.
Chromalveolates and rhizaria were clearly separate groups until we
published our results,” says Shalchian-Tabrizi.

“To make the picture a little less clear, one branch of
chromalveolates is still in no man’s land. It may be that these also
belong to SAR, but we will require additional genes and genomes to
study this. We have set our sights on doing that in the course of the
next few years,” he adds.

Fewer Events

“The Tree of Life tells the story of life on Earth, and our research
can say something about how quickly life developed. Our discovery
suggests that there were fewer big “events” than we have previously
assumed in the development of higher life forms. The more we know
about the branches on the Tree of Life, the more we can find out about
life’s Big Bang, the beginning of life on Earth,” says
Shalchian-Tabrizi.

Three billion years ago, there was only bacteria and Archaea.
Eukaryotic life, which comprises all multi-celled organisms, developed
in the sea—probably between 1.2 and 1.6 billion years ago. It was not
before about 500 million years ago that the first creatures crept onto
land.

“By digging down into the historical layers with the help of
phylogenetic reconstruction, where we can find out about kinship
between organisms at the genetic level and we can find answers to
questions about how new traits developed. We are working, in a matter
of speaking, with genetic archaeology. In this manner, we can also
discover the cause of the Earth’s biological diversity,” says
Jakobsen.

[Publisert 21.01.2008 ]




--
alias Ernest Major

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