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RE: Primitive life
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A mega asteroid bombardment four billion years ago may not have sterilised the early Earth as completely as previously thought. In fact, the asteroids, some the size of Kansas, provided a boost for early life.
The NASA-funded study focused on a particularly cataclysmic occurrence known as the Late Heavy Bombardment, or LHB. This event occurred approximately 3.9 billion years ago and lasted 20 to 200 million years.


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Tree of life
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A new and comprehensive analysis confirms that the evolutionary relationships among animals are not as simple as previously thought. The traditional idea that animal evolution has followed a trajectory from simple to complex - from sponge to chordate - meets a dramatic exception in the metazoan tree of life.
New work suggests that the so-called "lower" metazoans (including Placozoa, corals, and jellyfish) evolved in parallel to "higher" animals (all other metazoans, from flatworms to chordates). It also appears that Placozoans - large amoeba-shaped, multi-cellular animals - have passed over sponges and other organisms as an animal that most closely mirrors the root of this tree of life.

"To make inferences about the origin of Bilaterians - animals with a bilateral symmetry, like humans - earlier studies suggested sponges, ctenophores (comb jellies), or a small, interesting group called Placozoa as the most basal or primitive animal.  But our new analysis implies that the first major event in animal evolution split bilateral animals from all others, and our work firmly places Placozoa as the most primitive of the nonbilaterian animals" - Senior author Rob DeSalle, Curator at the Sackler Institute for Comparative Genomics at the American Museum of Natural History.

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Primitive life
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An evolutionary geneticist from the Université de Montréal, together with researchers from the French cities of Lyon and Montpellier, have published a ground-breaking study that characterises the common ancestor of all life on earth, LUCA (Last Universal Common Ancestor). Their findings, presented in a recent issue of Nature, show that the 3.8-billion-year-old organism was not the creature usually imagined.
The study changes ideas of early life on Earth.

"It is generally believed that LUCA was a heat-loving or hyperthermophilic organism. A bit like one of those weird organisms living in the hot vents along the continental ridges deep in the oceans today (above 90 degrees Celsius). However, our data suggests that LUCA was actually sensitive to warmer temperatures and lived in a climate below 50 degrees" - Professor Nicolas Lartillot, the study's co-author and a bio-informatics professor at the Université de Montréal.

The research team compared genetic information from modern organisms to characterise the ancient ancestor of all life on earth.

"Our research is much like studying the etymology of modern languages so as to reveal fundamental things about their evolution. We identified common genetic traits between animals, plant, bacteria, and used them to create a tree of life with branches representing separate species. These all stemmed from the same trunk - LUCA, the genetic makeup that we then further characterised" - Professor Nicolas Lartillot.

The group's findings are an important step towards reconciling conflicting ideas about LUCA. In particular, they are much more compatible with the theory of an early RNA world, where early life on Earth was composed of ribonucleic acid (RNA), rather than deoxyribonucleic acid (DNA).
However, RNA is particularly sensitive to heat and is unlikely to be stable in the hot temperatures of the early Earth. The data of Dr. Lartillot with his collaborators indicate that LUCA found a cooler micro-climate to develop, which helps resolve this paradox and shows that environmental micro domains played a critical role in the development of life on Earth.

The article, "Parallel adaptations to high temperatures in the Archaean eon," published in Nature, was authored by Bastien Boussau (CNRS, Université Lyon), Samuel Blanquart (LIRMM, CNRS: France), Anamaria Necsulea (CNRS, Université Lyon), Nicolas Lartillot (Université Montreal), and Manolo Gouy (CNRS, Université Lyon).

Source: University of Montreal

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-- Edited by Blobrana at 21:25, 2008-12-17

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Looking for fossils in old rocks is a tough job. Body parts degrade over the years, and the older the rock, the less likely it will be that you will find any evidence that life was once there. One question facing scientists is: Just how far back in time can we go before the traces of life are completely lost?
A new study provides one answer to that question, and in doing so suggests the limits to looking for ancient life not only on Earth, but also on other rocky worlds like Mars.

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Extremophile
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Hydrogen is the simplest, lightest, and most common element in the universe. Although the hydrogen molecule (H2) is highly reactive, and therefore rare in Earths atmosphere, it is usually found at parts per million levels in deep drill holes.
That hydrogen might be a mere curiosity or it might be relevant to the hot conditions where life seems to have originated. In 2005, Kenneth Nealson of the University of Southern California suggested that sub-surface microbial communities can get energy from hydrogen without needing any products of photosynthesis. And in 2006, Norman Pace of the University of Colorado reported that most of the microbes in Yellowstone National Parks hot springs get their energy from hydrogen, rather than from sulphur, as had been assumed.
If hydrogen is the energy source at the base of the food chain in those extremophile-rich locations, then it may have played the same role when the early ancestors of these bacteria first appeared on Earth and perhaps elsewhere.

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Researchers at Washington University in St. Louis and Arizona State University have sequenced the genome of a rare bacterium that harvests light energy by making an even rarer form of chlorophyll, chlorophyll d. Chlorophyll d absorbs red edge, near infrared, long wave length light, invisible to the naked eye.
In so doing, the cyanobacterium Acaryochloris marina, competes with virtually no other plant or bacterium in the world for sunlight. As a result, its genome is massive for a cyanobacterium, comprising 8.3 million base pairs, and sophisticated. The genome is among the very largest of 55 cyanobacterial strains in the world sequenced thus far, and it is the first chlorophyll d containing organism to be sequenced.

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Scientists studying microbial communities and the growth of sedimentary rock at Mammoth Hot Springs in Yellowstone National Park have made a surprising discovery about the geological record of life and the environment.
Their discovery could affect how certain sequences of sedimentary rock are dated, and how scientists might search for evidence of life on other planets.

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The Tree of Life Has Lost a Branch
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.
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 resourcessupplied through a large network of computers at the University of Oslo.

The results were pretty astounding. All non-bacterial life on Earthcalled eukaryotic life can now be divided into four main groups instead of the five groups that we have been working with up to now - Kamran Shalchian-Tabrizi, an associate professor from the University of Oslos 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 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.

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. 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 - Shalchian-Tabrizi in an interview with the University of Oslos research magazine Apollon.

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 - Professor Kjetill S. Jakobsen from the University of Oslos 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.
All life on Earth can be divided into two essentially different life formseukaryotes 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 organismssuch as humanscan, 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 animalsincluding humans)
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. To make the picture a little less clear, one branch of chromalveolates is still in no mans 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. 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 lifes Big Bang, the beginning of life on Earth - Shalchian-Tabrizi.

Three billion years ago, there was only bacteria and Archaea. Eukaryotic life, which comprises all multi-celled organisms, developed in the seaprobably 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 Earths biological diversity - Kjetill S. Jakobsen.

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The crystal structure of a molecule from a primitive fungus has served as a time machine to show researchers more about the evolution of life from the simple to the complex.
By studying the three-dimensional version of the fungus protein bound to an RNA molecule, scientists from Purdue University and the University of Texas at Austin have been able to visualize how life progressed from an early self-replicating molecule that also performed chemical reactions to one in which proteins assumed some of the work.

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The Five Kingdoms
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Biologists today have classified and divided all living things into five groups they call Kingdoms. These kingdoms are based on how living things are the same, and how they are different. Biologists are still learning about our world, and are making new discoveries every single day. As our knowledge about the world around us improves, scientists might find a better way to organise and classify life. As a result, these five kingdoms may someday change.

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