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Viewings: 3866When on land, there came life? The answer to this question is one of the fundamental science) depends primarily on the meaning of "life" and "land".
There is clear evidence of life in fresh water (in small ponds, to be precise), which is a billion years or so. All other evidence is indirect, derived from the characteristics of weathering non-marine species, and the presence of fossilized relic of soils. Actual resources which can address the question of the existence of terrestrial life in Precambrian (more 542 million years ago), are extremely rare. Some call them mythical.
Perhaps, the mysterious Dickinsonia were not at all marine life, and one of the first "land of rats". (Photo By G. Retallack.)
This is a very difficult topic in the study of which it is impossible to avoid criticism and accusations of trying to produce a sensation. One of those who was not afraid of it, was Jane grey, paleobotanic. Since 1950-ies she defended (often loudly) hypothesis early development of life on land. Because she was a woman, and the still-eater, and a supporter unpopular theory, it did not feel sorry grants. But, as he wrote the obituary biologist William Sir, she interpreted fossil disputes with the shrewdness of a player on the market and financed his studies at the expense of own state.
Today, Jane grey is a worthy successor. Gregory Retallack from the University of Oregon (USA) is also not afraid title scientist-the heretic. For many years he is working relic soil from the Precambrian. The problem with fossil ground that it is recognized as such by the traces of organisms that lived in it, first of all by plant roots. But what about the soil in which the roots are not left? In this case we have to deal with jewelry geological work: it is necessary to show that paleosol associated with the breed, resulting in non-marine conditions, and perform geochemical and isotopic analysis. Meet and sometimes direct pointers that before scientists soil, is carbonate concretions, crystals sand and cracks caused by shrinkage or the presence of ice.
Evidence of this kind, and brought Mr. Metallica to the conclusion that among ediacarian rocks (635-542 million years ago) South Australia, he was able to detect paleosol. It would seem, what's difficult is only the last period of pre-Cambrian, not so long ago it was. But these rocks contain a very rich evidence of the first macroscopic life, which, according to most, was the sea.
In ediacarian rocks found many large, well-marked, but the mysterious formations, which is usually interpreted as the remains of living things. First ediacarian fossils were discovered in South Australia, and later - on the canadian island of Newfoundland, and in the Russian Arctic, and in the Midlands of England.
These very strange fossils. Although there is no doubt that these organisms of vysokoorganizovannymi what they are, is not clear. If they were animals, little or completely not similar to other beings - neither resources, nor modern. This led to the assumption that they were giant protozoa, fungi, algae, lichens, or even a form of life that was completely different from anything we had to deal with, and which has since become extinct.
Perhaps the only point on which reached General consensus is that, whatever it was, ediacarian biota dwelt on the sandy bottom of shallow sunlit seas. That's where the way Mr. Metallica disagree with almost all, because some of his ediacarian soils are associated with ediacarian resources. This means that at least part of ediacarian biota (not so small and not mythical) lived on land, under the open sky - perhaps in the manner of lichens or colonies of microorganisms that form the soil crust. That's who, according to Mr. Metallica, first inhabited land, not the basins, and the soil dry and cold deserts. It's not just contrary to generally accepted hypothesis, it -- it -- it's inconceivable! There is no doubt that paleontologists now breathe deeply and will begin dump.
The only way to prove Mr. Metallica is work and work. You may recall the example of the same Jane grey. When she was proving the existence of terrestrial life in the Ordovician (485-443 million years ago), it was waving hands. Now it is a dogma. By the way, there is nothing unnatural in that life in one form or another (probably the most modest) could be selected on the land and in the Precambrian. Besides, this is not necessarily happened once in the history of evolution.
But in General - it is time to realise: the fossil record has one nice feature. When all is clear, suddenly there is something that takes science in unexpected and exciting, interesting direction.
The study is published in the journal Nature.
Based on the materials of Nature News.
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