* Astronomy

Biologists examining ecosystems similar to those that existed on Earth more than 3 billion years ago have made a surprising discovery: Viruses that infect bacteria are sometimes parochial and unrelated to their counterparts in other regions of the globe.
The finding, published online this week by the journal Nature, is surprising because bacteria are ubiquitous on Earth. They've been found from the upper reaches of the atmosphere to miles below the ocean floor. Because of their ubiquity, scientists have long believed bacteria to be cosmopolitan, having similar genetic histories across the globe. The same was also believed to be true for phages, the viruses that infect bacteria.
Bacteria are the dominant forms of life on Earth. They helped shape the planet's land, oceans and atmosphere for 3 billion years before the first appearance of multicellular creatures. Siefert and several of her co-authors began traveling to Cuatro Ciénegas in Mexico's Chihuahuan Desert in 2004 to study cyanobacteria living in a network of more than 200 spring-fed pools, or pozas. Cuatro Ciénegas' pozas have been compared to the Galapagos Islands, except that their endemic species -- at least 70 species in the valley are found nowhere else on Earth -- are separated from the rest of the world by mountains and a sea of sand rather than an ocean.
The cyanobacteria in the pozas live communally, forming coral-like structures called "stromatolites," or microbialites, that are geologically identical to 3.5 billion-year-old fossils that are believed to be the oldest evidence of life on Earth.
Stromatolite samples collected from two pozas in 2004 were examined by several co-authors in the research group of San Diego State University biologist Forest Rohwer, who has prepared the world's largest database of phage DNA. In the first step of the tests, researchers crushed small bits of the coral-like stromatolites and extracted DNA from the samples. The DNA from each sample was decoded and compiled into a database called a "metagenome." The metagenomes from the Mexican pozas were compared with each other and with metagenomes from stromatilites in Highborne Cay, Bahamas. Finally, all three of these metagenomes were compared with Rohwer's phage database and with several large gene-sequence databases, like GenBank.

"Taken together, these results prove that viruses in modern microbialites display the variability of distribution of organisms on our planet. It also suggests that they may be derived from an ancient, microbial community" - biologist Forest Rohwer, San Diego State University.

The analyses found that the phages in the Bahamas and in both Mexican pozas shared only about 5 percent of the same DNA sequences. Moreover, the analyses revealed that the Mexican phages appeared to have evolved from ancient, ocean-going relatives. Siefert said the finding is amazing given that Cuatro Ciénegas has been cut off from the ocean for about 100 million years, but it complements prior findings of marine genetic signatures in some of Cuatro Ciénegas' other endemic species.

The work drew interest and seed funding from NASA's astrobiology program, which hoped the work might provide important clues about the way early life might develop on other planets.

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Scientists have known for some time that most major groups of complex animals appeared in the fossils record during the Cambrian Explosion, a seemingly rapid evolutionary event that occurred 542 million years ago. Now Virginia Tech palaeontologists, using rigorous analytical methods, have identified another explosive evolutionary event that occurred about 33 million years earlier among macroscopic life forms unrelated to the Cambrian animals. They dubbed this earlier event the "Avalon Explosion."
The discovery, reported in the January 4 issue of Science, suggests that more than one explosive evolutionary event may have taken place during the early evolution of animals.
The Cambrian explosion event refers to the sudden appearance of most animal groups in a geologically short time period between 542 and 520 million years ago, in the early Cambrian Period. Although there were not as many animal species as in modern oceans, most (if not all) living animal groups were represented in the Cambrian oceans.

"The explosive evolutionary pattern was a concern to Charles Darwin, because he expected that evolution happens at a slow and constant pace. Darwins perception could be represented by an inverted cone with ever expanding morphological range, but the fossil record of the Cambrian Explosion and since is better represented by a cylinder with a morphological radiation at the base and morphological constraint afterwards" - Shuhai Xiao, associate professor of geobiology at Virginia Tech.

Darwin reckoned that there should be long and hidden periods of animal evolution before the Cambrian Explosion.
But palaeontologists have not found such evidence, and recently scientists have learned that biological evolution has not been moving on a smooth road.

Accelerated rates may characterise the early evolution of many groups of organisms - Michal Kowalewski, professor of geobiology at Virginia Tech.

To test whether other major branches of life also evolved in an abrupt and explosive manner, Virginia Tech graduate students Bing Shen and Lin Dong, along with Xiao and Kowalewski, analysed the Ediacara fossils: the oldest complex, multicellular organisms that had lived in oceans from 575 to 542 million years ago; that is, before the Cambrian Explosion of animals.

"These Ediacara organisms do not have an ancestor-descendant relationship with the Cambrian animals, and most of them went extinct before the Cambrian Explosion. And this group of organisms most species seems to be distinct from the Cambrian animals. But how did those Ediacara organisms first evolve. Did they also appear in an explosive evolutionary event, or is the Cambrian Explosion a truly unparalleled event. We identified 50 characters and mapped the distribution of these characters in more than 200 Ediacara species. These species cover three evolutionary stages of the entire Ediacara history across 33 million years - Shuhai Xiao.

The three successive evolutionary stages are represented by the Avalon, White Sea, and Nama assemblages (all named after localities where representative fossils of each stage can be found). The earliest Avalon stage was represented by relatively few species.
Surprisingly, however, as shown by Shen and colleagues, these earliest Ediacara life forms already occupied a full morphological range of body plans that would ever be realised through the entire history of Ediacara organisms.

"In other words, major types of Ediacara organisms appeared at the dawn of their history, during the Avalon Explosion. Subsequently, Ediacara organisms diversified in White Sea time and then declined in Nama time. But, despite this notable waxing and waning in the number of species, the morphological range of the Avalon organisms were never exceeded through the subsequent history of Ediacara"

Kowalewski said their research team had not anticipated the discovery.

Using the scientific literature, we were trying to create a more rigorous reconstruction of the morphological history of Ediacara organisms - Michal Kowalewski.

The process involved adapting quantitative methods that had been used previously for studying morphological evolution of animals, but never applied to the enigmatic Ediacara organisms.

We think of diversity in terms of individual species. But species may be very similar in their overall body plan. For example, 50 species of fly may not differ much from one another in terms of their overall shape they all represent the same body plan. On the other hand, a set of just three species that include a fly, a frog and an earthworm represent much more morphological variation. We can thus think of biodiversity not only in terms of how many different species there are but also how many fundamentally distinct body plans are being represented. Our approach combined both those approaches. In addition, the method relies on converting different morphologies into numerical (binary) data. This strategy allows us to describe, more objectively and more consistently, enigmatic fossil life forms, which are preserved mostly as two-dimensional impressions and are not understood well in terms of function, ecology, or physiology - Michal Kowalewski.

Scientists are still unsure what were the driving forces behind the rapid morphological expansion during the Avalon explosion, and why the morphological range did not expand, shrink, or shift during the subsequent White Sea and Nama stages.

"But, one thing seems certain -- the evolution of earliest macroscopic and complex life also went through an explosive event before to the Cambrian Explosion. It now appears that at the dawn of the macroscopic life, between 575 and 520 million years ago, there was not one, but at least two major episodes of abrupt morphological expansion" - Shuhai Xiao.

Source Virginia Tech

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Fossils of jellyfish found in Utah resemble creatures of today
The fossil remains of fragile jellyfish that lived some 505 million years ago have been discovered in the rocks of a Utah mountainside that once lay at the bottom of a shallow tropical sea.
The ancient fossils are strikingly similar to modern jellyfish, indicating that when those animals evolved they were so ideally suited for their environment that their form and structure must have remained virtually unchanged for a long, long time.

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Researchers from Kent State University and the University of Bucharest, Romania, have discovered a new primitive crab species Cycloprosopon dobrogea in eastern Romania. Previously unexamined, these ancient crabs from the Prosopidae family existed more than 150 million years ago during the Jurassic period.

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