Perm extinction is the most ambitious extinction of species on the planet for the entire geological history, which happened on Earth about 250 million years ago. The most common hypothesis about the causes of this extinction - volcanic - recently received a new confirmation of paleogeologists.
If you look at the textbook geochronological table, on the timeline of which geological era and periods are accompanied by a description of the dominant flora and faun, we will see that completely different forms dominated triacs on Earth after the Perm period. In the end of Perm, the ancient forests from giant plauines and ferns disappear (these are now actively developed by coal deposits), populated by lizard-like amphibians, and coniferous ones come to replace them. In the animal kingdom, the Late Perm Epoch was marked by the appearance of real lizards - large reptilewho have determined the entire appearance of the subsequent Mesozoic era in the ideas of modern schoolchildren and advanced journalists.
Perm extinction ended with Paleozoa, launched 420 million years. Perm extinction released a place for mesozoic flora and fauna on the planet.
The reason for such a grand shift of classes of plants and animals on the border of the Paleozoic and Mesozoic lies in a catastrophic change of global tropical climate moderate and substantial change in chemical composition earthly atmosphere. And these changes are caused volcanic activity On the territory of modern Siberia.
In those distant geological times of Siberia, as such did not exist. There was no Europe, nor Asia, nor the Eurasian continent. And there was a single supermaith Pangea, which included in his composition of Africa, Antarctica, Australia and both America. And there was the only ocean, washing the pantala from all sides - the superokean of Pantalass.
But here is 252 million years ago for some reason (the reason is still a discussion question) Supervulkans were activated. Their most powerful eruptions for the Millennium closed sunlightthrowing into the atmosphere great amount Dust and soot. There was a long era of twilight with a common cooling, which was not able to survive the tropical paleozoic forests with their amphibian population. For some 50 thousand years catastrophically extinct 65-70% terrestrial species. In science, this extinction is known as the Perm biosphere catastrophe.
But the grand perm extinction of terrestrial flora and faun, it turns out that only a weak reflection of the biosphere catastrophe, which happened a little later in the world ocean of the Pantalassa. According to estimates of paleontologists, 90% of the inhabitants of the underwater world were extinct.
Emission of aggressive volcanoes chemical substances The atmosphere caused sulfate, nitric acid and other acid rains. Dust deposited on an extensive water surface also contained acid radicals. But the main factor was CO2 carbon dioxide, in incredible quantities - trillions of tons! - in the atmosphere due to volcanic emissions, and secondary way - due to total forest fires. In general, poorly dissolving in water, carbon dioxide, nevertheless came to her in huge quantities. And dissolving, turned into carbon dioxide H2CO3 (this is the one that has a tongue pluglet in the gas.
For some 10 thousand years of water of the world oxidized, the pH of the aqueous medium has dropped sharply at once (by geological standards) by 0.7 units. And the ocean of Pantalassa for a long time empty.
All of the above is the result of long and painstaking research of geologists, geochemists, paleontologists of different countries, on crumbs mining new knowledge about the distant past of our planet.
The last time (but not the final) contribution was made by geologists, studying Perm limestone deposits in the territory of the United Arab Emirates (UAE) on the Persian Gulf Coast. Scientists investigated the content of two boron isotopes in biogenic limestone. These two varieties of atoms of one chemical element They differ in concentrations in alkaline and acidic waters, which is a marker to determine the pH of the aquatic environment in which the Perm Shell-Shells, Shells of Foraminifera and other marine organisms with a lime skeleton were sometimes dwelling. From their skeletons through millipatia and limestones were formed, which came to this day.
Geologists came to the conclusion that the water in the area in the Late Perm Epoch had increased acidity. These studies have confirmed the correctness of the similar conclusion of other specialists regarding calcium isotopes in the same limestones.
The results obtained, of course, a sensation (as it was presented to the media) can not be called - just another grace in the brick of the grand skyscraper of modern science. But the "brick" himself is in a sense of the cornerstone.
According to the scientists themselves, their work allowed to find out the reasons for the second extinction (Pantalassian) animals in the Late Perm Epoch, but does not explain the decline species diversity During the first extinction, which happened for several tens of millennia earlier and lasted 50 thousand years. As indicated by paleogeological data, the acidity of the aqueous medium at this first stage of extinction also increased, but slightly.
How can I interpret these data on the Lamermist Limestones of the Arabian Peninsula? Obviously, they prove once again that the volcanic activity of late Perm led to the biosphere revolution and two-stage extinction of biota on the planet.
The first extinction is ground flora fauna - described above. It was the result of a climate catastrophe (blackout ground surface and a decrease in global temperature on land due to contamination and toasting the atmosphere with seizureless particles, discarded volcanoes and fires). That is, here we have an analogue of the famous mathematical model of the "nuclear winter", first described by Karl Sagan and in detail the studied computing center of the USSR Academy of Sciences in the early 1980s under the leadership of Academician N.Muiseev (Mir-3 model).
The second, unprecedented extinction - the hydrobiota of the ocean Pantasy, which followed after the first ground extinction after a short geological lapse of the time (the famous mathematical analogues does not have). It is caused by chemical contamination of the atmosphere and surface water and acid-forming anhydrides and, as a result, the secondary pollution of the ocean ocean as a result of the dissolution of anhydrides (first of all - CO2) in water. Although carbon dioxide is less aggressive than acids with nitrogen-sulfur-chlorine-containing radical residues, and the dissolution of CO2 is very mediocre in water, but its amount in the atmosphere was phenomenally large. And time - abound. As a result, precisely carbon dioxide entered into the atmosphere from the "Siberian" volcanoes and burning fern jungle strongly screamed the world ocean. This is a change in the chemical station and the acidity of the usual for Perm marine inhabitants Wednesdays and destroyed them.
Carbon dioxide carbon dioxide formed coalic acid H2CO3, which reacted with the omnipresent calcium to form a hard-soluble salt Saso3, simply limestone. Water organisms survived in the Apocalypse with a lime skeleton were removed from the solution. The rich content of lime in the water gave an outbreak of calcium-containing organisms. For many millions of years, they thus gradually removed the carbon dioxide dissolved in water, accumulating it in the form of completely insoluble lime sediments of shells, limestone (mollusks), chalk (foraminifera). That is, the acidity of ocean water returned in the former (or today) neutral state. And after herself left the rikushnyak, who gradually turned into the deposits of chalk and limestone. And some of them went further and, in turn, through millipatia turned into calcites, dolomites, mergels and marble - that is, in valuable building materials.
It concerns scientific value Described work on the study of late Perm limestone.
But from this work of geologists, one more important conclusion follows (they themselves focus on this): Mass extinction of animals may be a warning of a person due to its active industrial activities, leading to the emission of the Earth's atmosphere carbon dioxide. It is with her that scientists associate an increase in the average pH in the ocean to date by 0.1 from the beginning of the industrial revolution.
Top, reader, attention: for the acidification of volcanoes and fires Bronaisana Pantalass for 0.7 hydrogen units required tens of thousands of years. The industrial revolution in England began only 300 years ago, in Russia - 200, and someone in the world, she has not yet risen. But for this historical (and not geological!) The gap of the ocean has already managed to cry at 0.1 units. It suggests a comparative conclusion from which the hair on the head will move!
According to geological standards, one of the most catastrophic extinction in the history of the Earth that happened in perm periodIt continued literally an instant. According to researchers from the Massachusetts Institute of Technology, 96% of water species and 70% of terrestrial species died in just 60 thousand years. Nothing like this in the history of our planet has not happened since then.
To get a stunning figure of 60 thousand years, scientists succeeded due to new, more accurate methods for determining the age of rock.
"We have an idea of \u200b\u200bthe exact age and duration of extinction, - stated Professor of the Geological Faculty of Mit Sam Bowring. - But how could I kill 96% of all the inhabitants of the oceans for any tens of thousands of years? It seems that exceptional extinction requires an exceptional explanation. "
Approximately 10 thousand years before the catastrophe of the oceans of the Earth were exposed to a large amount of carbon's lung isotopes. As a result, the water was strongly acidified, and its temperature rose at once with 10 degrees. It was these events that destroyed most marine inhabitants, researchers are confident.
As you know, mass perm extinction is one of five mass extinction. There was a border between Perm and Triassic geological periods (it also shares the Paleozoic and Mesozoic era). The age of this border in modern (2012) geochronological scale is 252.2 ± 0.5 million years.
This is one of the largest catastrophes Biospheres in the history of the Earth, which led to extinction of 96% of all sea species and 70% of ground vertebrate species. The catastrophe became the only known mass extinction of insects, as a result of which about 57% of the birth and 83% of the species of the entire class of insects died out. Due to the loss of such quantity and diversity biological species Restoration of the biosphere occupied much more a long period time compared to other catastrophes, resulting in extinction.
The models for which the extinction proceeds is in the process of discussion. Various scientific schools suggest from one to three jolts of extinction.
The extinction was rapidly (no more than 200 thousand years continued), synchronous to the sea and on land, accompanied by mass fires. Presumably, his cause was a sharp release of greenhouse gases, caused by trapping magmatism in the territory of the current Siberia, which led to a significant overheating of the planet and drought. The first tropical forests were killed, the other vegetation was followed by them, the result of which was a sharp increase in erosion and the death of soil.
Currently, specialists have a generally accepted opinion on the causes of extinction. A number of possible reasons are considered.:
– catastrophic events:
- strengthening volcanic activities in Siberia;
- the fall in one or many meteorites, or the collision of the earth with an asteroid with a diameter of several tens of kilometers (one of the evidence of this hypothesis is the possible presence of a 500-kilometer crater in the region of Wilx Earth);
- Sudden emitting methane from the bottom of the sea;
- Acquisition by Archey (genus Methanosarcina) ability to process the organic with the allocation of large methane volumes.
– gradual Environmental Changes:
- Anoksia - changes in chemical composition sea water and the atmosphere, in particular, the deficiency of oxygen;
- increase in climate dryness;
- the change oceanic flows and / or sea level under the influence of climate change;
The most common hypothesis, according to which the cause of the catastrophe was the outpacing of the trappers (at the beginning of about 260 million relatively small email traps, then the colossal Siberian trappers 251 million years ago), which could entail a volcanic winter, a greenhouse effect due to volcanic emission Gas and others climate changewho influenced the biosphere.
The evidence that the fall in asteroids could cause a lateral catastrophe, give rise to hypotheses that similar events could also cause other mass extinction events, including the Perm extinction, and to verify these hypotheses are being searched for craters of the corresponding sizes.
In Australia and Antarctica, evidence of the existence of shock events corresponding to the Permian period was found: the grain of impact quartz, fullerenes with the inclusions of inert gases of extraterrestrial origin, fragments of meteorites in the Antarctic and the grade containing elevated level Iron, nickel and silicon - possibly shock origin. However, the accuracy of the majority of these studies is very dubious. For example, Quartz from the Antarctic, which was considered having a shock origin, was recently investigated using optical and electron microscopes. As a result, it was revealed that the samples found were formed, most likely, as a result of plastic deformations in solid bodies, and not from shocks in tectonic processes like volcanism.
As traces of meteorites that caused mass perm extinction, consider several crater (possibly shock origin), including the structure of the Bedout in the northeastern part of Australia and the hypothetical crater of Wilx Earth in Western Antarctica. In each of these cases, the hypothesis of the cosmic strike did not receive confirmation and was criticized. And in the case of the Earth Wilx, the age of these geological formations is definitely not defined and can relate to later periods.
As a result of mass extinction from the face, many species disappeared, went into the past whole numbers and even classes; Most of the graduating troops (except the ancestors of modern turtles), many species of fish and arthropods (including trilobites). Rebuilt sea ecosystems: The role of the reeformation agents is moving from Mshanok to corals, bottom filtots - from the shoulder to bivalve mollusks.
The cataclysm also hit the world of microorganisms.
As a result, our planet is strongly empty. Some scientists are generally believed that the Earth was in the mercy of fungi, fed to the remnants of the dead organisms.
It is believed that about 30 million years left for the restoration of the biosphere after the mass extinction, but some scientists make conclusions that it could occur in a shorter period of time, about 5-10 million years. When restoring the biosphere, opportunistic organisms were widespread: mushrooms, bacterial mats, plane-shaped Pleuromeia plants.
Perm extinction completed the period of prosperity of the synapside (although with a dozen species survived) and the anapsid reptiles, giving the way to many animals, for a long time The remaining in the shadows: the beginning and the middle of the next triad period of the Triassic period were marked by the formation of arhozavrov, from which dinosaurs and crocodiles occurred, and afterwards the bird.
They survived those species that were more adapted to new conditions: overheating, lack of oxygen, disadvantage of food, excess of sulfur in water, etc. Although, of course, the survival or extinction of many species was random. If the distribution area of \u200b\u200bthis species turned out to be a small portion, on which acceptable habitats were preserved, the probability of survival was higher. Thus, some plants in Australia have successfully survived.
In addition, it is in Triassa that the first mammals appear. Before the beginning of the Triass, it was possible to live a small part of the warm-blooded besera-like tetrapeods - zinosnonts. Triasss themselves did not survive the cosnonta, but their descendants managed to stand in the chalk extinction that destroyed all the dinosaurs, and put the beginning new group Animals - mammals, followed by the future of our planet.
Perm extinction has become one of the largest catastrophes that happened for long history Earth. The Planet's biosphere lost almost all marine animals and more than 70% of ground representatives. Did scientists understand the reasons for extinction and evaluate its consequences? What theory are put forward and can they believe them?
Perm period
To roughly submit a sequence so distant events, it is necessary to refer to the geochronological scale. Total Paleozoic has 6 periods. Perm - the period on the border of Paleozoic and Mesozoic. Its duration of 47 million years (from 298 to 251 million years). Both era, and Paleozoa, and Mesoza, are part of the plywood eon.
Each period of the Paleozoic era is interesting and rich in the events. In the Perm period there was an evolutionary impetus that developed new forms of life, and the Perm extinction of species, destroying most Animal land.
What is the name of the period
"Perm" - an amazingly familiar name, you do not seem? Yes, you are not mistaken, it has Russian roots. The fact is that in 1841 a tectonic structure was discovered corresponding to this period of the Paleozoic era. Nakhodka was located near the city of Perm. And the entire tectonic structure today is called the priestly regional deflection.
The concept of mass extinction
The concept of mass extinctions was introduced into scientific turnover by scientists of the University of Chicago. The work was carried out by D. Sepkoski and D. Raup. According to statistical analysis, 5 mass extinction and almost 20 smaller disasters were allocated. It was taken to consider the information for the last 540 million years, as for more early periods Data is not enough.
The largest extinction includes:
- ordigrian-silurian;
- devonian;
- perm extinction of species (the reasons for which we consider);
- triassoy;
- mel-Paleogenic.
All these events took place in Paleozoic, Mesozoic and cenozoic era. Their frequency of 26 to 30 million years, but many scientists do not accept the established periodicity.
The greatest ecological catastrophe
Perm extinction is the most massacre in the history of our planet. Sea fauna extinct almost completely, terrestrial species have survived only 17% of the total. More than 80% of insect species have died out, which did not happen during other mass extinction. All these losses happened about 60 thousand years, although some scientists suggest that the period of mass Mora continued about 100 thousand years. Global losses that have brought a large Perm extinction, conducted a final line - crushing it, the biosphere of the Earth began evolution.
The restoration of the fauna after the greatest ecological catastrophe continued for a very long time. It can be said that much longer than after other mass extinction. Scientists are trying to recreate the models for which the massive mass could flow, but so far they cannot even come together in the amount of jokes inside the process itself. Some scientists believe that the great Perm extinction of 250 million years ago had 3 peak shock, other scientific schools tend to the fact that there were 8.
One of the new theories
By assumptions of scientists, another mass catastrophe was preceded by Perm dying. It happened 8 million years before the main event and significantly undermined the Earth's ecosystem. The animal world has become vulnerable, so the second extinction within one period turned out to be the greatest tragedy. If we manage to prove that in the Perm period there were two extinction, then the concept of frequency will be in doubt mass disasters. Justice to clarify that this concept is disputed from many positions, even without taking into account possible additional extinction. But this point of view while keeps scientific positions.
Possible causes of Perm catastrophe
Perm extinction still causes many disputes. Acute controversy unfolds around the causes of the ecological cataclysm. As equivalent, all possible grounds are considered, including:
- external and internal catastrophic events;
- gradual changes in the environment.
We will try to consider some components of both positions in more detail in order to understand how much the likelihood of their influence on the Perm extinction is. Photos of confirming or refuting finds provide scientists from many universities as the issue is examined.
Catastrophe as the cause of Perm extinction
External and internal catastrophic events are customary to consider as the most likely causes of great extinction:
- During this period, there was a significant strengthening of volcanoes on the territory of modern Siberia, which led to a great outpouring of the trapps. This means that there has been a huge eruption of basalt for a short time in geological concept. Basalt is weakly susceptible to erosion, and the surrounding sediments are easily destroyed. As evidence of trapping magmatism, scientists lead as an example of huge territories in the form of flat stepped plains on the basalt base. The largest trapping terrain is the Siberian trapp formed at the end of the Perm period. Its area is more than 2 million km². Scientists of the Nanking Institute of Geology (China) conducted a study of the isotopic composition of the rocks of Siberian trappers and found that the Perm extinction occurred during their education. It took no more than 100 thousand years old (before that it was believed that it took a longer period of time - about 1 million years). The activities of volcanoes could provoke a greenhouse effect, volcanic winter and other processes descended for the biosphere.
- The causes of the biosphere catastrophe could be a fall in one or more meteorites, with a large asteroid. As evidence, a crater is a square of more than 500 km (Wilx, Antarctica land). Also evidence of impact events found in Australia (the structure of the Bedout, northeast of the continent). Many of the obtained samples were later refuted in the process of a deeper study.
- One of the possible reasons is considered a sharp emission of methane from the bottom of the seas, which could lead to the total death of marine animal species.
- A catastrophe could be obtained by one of the living domains unicellular organisms (Archaei) ability to process the organicity, highlighting large volumes of methane.
Gradual changes in the environment
- The gradual changes in the composition of sea water and the atmosphere, as a result of which an ignition appeared (lack of oxygen).
- Increasing the dryness of the land climate - the animal world could not adapt to changes.
- The consequence of climate change has become disorders of oceanic flows and a decrease in sea level.
Most likely, a whole range of reasons influenced, since the catastrophe was massive, and occurred in a short period.
The consequences of a great extinction
Great Perm extinction, the reasons for which is trying to establish scientist MirThere were serious consequences. Fully disappeared entire detachments and classes. Most of the paradities extinced (only ancestors of modern turtles remained). A huge number of types of arthropods and fish disappeared. The composition of microorganisms has changed. In fact, the planet was empty, being in the mercy of fungi feeding on Padalu.
After the Perm extinction survived, the species as adapted to overheating, low level Oxygen, disadvantage of food and excess sulfur content.
Mass biosphere cataclysm opened the road to new animal species. Triass, the first revealed the world of Arhozavrov (the progenitors of dinosaurs, crocodiles and birds). After a great extinction on Earth, the first types of mammals appeared. On the restoration of the biosphere, it took from 5 to 30 million years.
In the first third of the XIX century, when William Smith founded science to stratigraphia, scientists preferred to explain the presence of the remains of the remains of several fossil faun in the geological rocks using the so-called theories of disasters, or catastrophizma (not to be confused with the mathematical theory of the same name). According to this theory, animals and plants on Earth existed unchanged from the moment of creation and until a global cataclysm fell on their heads, and gigantic waves buried under a powerful layer of snack, sand and clay all living things. Or the firewood volcanoes poured the earth's surface of lava and poured hot ashes. After that, on our planet there was absolutely new lifeWhat implies a re-act of creation. However, the Father-founder of the theory of the catastrophe Georges Cuvier did not insist on multiple creation. He believed that new species moved to the lifeless areas from remote areas not affected by a natural disaster. After some time, these areas, in turn, were amazed by the cataclysm and disappeared into the sea underlying without a trace. That is why new species appeared as if anyway.
TO mid XIX. in. The minds took the idea of \u200b\u200ba smooth, gradual and continuous evolution. More than other such changes in the sentiments of the scientific community contributed to the works of two Charles - Charles Lileel and Charles Darwin. The first expressed and substantiated the assumption that powerful geological layers under which the remains of organisms are buried, not always traces natural disaster. Most often this is the result of the centuries-old accumulation of precipitation falling in a normal, rather than a catastrophic pace. The second, inspired by the ideas of the first, created a slim theory of gradual evolution organic Worldwhich we all studied at school.
The most famous representative of the Sfenakodontov - Dimetrodon (Dimetrodon). This is a Ranneperman, which included several species
For some time, the Cuvier catastrophe Theory was almost forgotten, as it turned out, not well deserved. Modern biological views are essentially a certain synthesis of catastrophesis and the theory of smooth continuous evolution. That is, changes in the guise of species, of course, occur constantly, but most of the history of the Earth they accumulate well very slowly. In normal established conditions, natural selection is rather a stabilizing mechanism, with greater probability with cutting any innovations. But a certain factor appears, irreparably violating the equilibrium achieved earlier. Century-old swamps are breathing rapidly, forests disappear, the temperature and the chemical composition of the air, the acidity of water changes. Billions of living beings are dying, without leaving the offspring. The number of species living on earth is steadily reduced.
And with such sad circumstances, there are always species that previously occupied a very modest position in the ecosystem, but possessing any signs that allow you to survive this catastrophe. In conditions mass death Competitors, they go to the forefront and are developing rapidly. Natural selection begins to fix the previously cut-off signs necessary in the new conditions. The descendants of the former outsiders populate the land empty after the cataclysm, and soon (in the geological sense of the word), its appearance changes in the root.
It is precisely because evolution proceeds not entirely smoothly, and we observe the removal to extinct, we are observing the relatively clearly delineated geological periods, temporary segments, inside which does not occur with a sharp change of fauna and flora. At the same time, in the middle of the period, some species gradually go from the scene and replaced by others. It is like a background level of extinction. But at the borders of periods, the number of disappeared species per unit of time is much higher. If there are tens of millions of years on average for a substantial change in fauna and flora, then at certain areas of the geochronological scale full shift Scenery can meet the "total" in 2 -3 million years. But within the life of one separately taken individual, such an ecological catastrophe, if lucky, can not be noticed.
The greatest ecological catastrophe in the history of the earth
After analyzing the dynamics, the disappearance of species, paleontologists have discovered five particularly high peaks that are significantly towering over the background level. Very large, emerging out of the row of extinction are observed in the Late Cambrian, Late Devon, Late Perm, Late Triassa and Late Chalk. The last of the listed includes intriguing so many deaths of dinosaurs. However, the extinction at the end of the chalk period is not the largest ecological catastrophe in the history of land. The title of great extinction by right is a cataclysm, which took place about 250 million years ago at the border of the Perm and Triassic periods. He also shares Paleozoic and Mesozoic geological era.
As far as can be judged by paleontological data, as a result of the great Perm extinction from the face of the Earth, 70% of the species inhabited its previous vertebrates and 90% of all inhabitants of the sea disappeared forever. By the same time there is the only massive intake of insects in the history of the earthly biosphere (about 80% of all species). For comparison, at the end of the chalk period, less than 20% of all types of animals extinct on the border of the Mesozoic and Cenozoic. The world of insects, the most numerous in the number of species, this catastrophe touched on a little.
The border layers at the junction of Perm and Triass differ from an exceptionally low variety of species. The restoration of the Biosphere of the Earth after a great extinction by different estimates left 5 to 30 million years. By the end of this period, life on our planet was boiling again, but acquired a completely different appearance. What was this disappeared world, and what did he distinguish from what came to shift?
It was so it turned out that out of all the livelihood of a person most interested in the nearest rings - ground vertebrates. It is them (if any) remember first of all, answering the question of which animals are found in one area or another. So, let's, perhaps, from the ground vertebral Perm period, especially since they are very noteworthy. But first - a small excursion to an even more distant past.
Competition on land
The output of vertebrate animals on land took place in the Devonian geological period. Pioneers in the development of the new living space became amphibians (amphibians). Their further evolution outside the aqueous space led to the improvement of the mural respiration and the transformation of eggs, which can develop only in an aqueous medium, in eggs with a solid shell or a dense leathery. It allows the larva to develop as it were in a tiny water binding, located inside the embryo shell - Amnion.. Higher vertebrates - happy owners of such a shell are called amniotami. Next, among the amniotes, there were two branches of the animal world - prombromorphs (from the Greek "Zauros" - Lizard) and terromorphs (from the Greek "Terion" - a beast).
The first in addition to the above devices acquired dry skin with a horn coating, minimizing moisture loss. Creatures, dressed in such "deserted spaces" do not need any large reservoirs and can safely come deep into the mainland, without fearing to break away from water sources. However, for convenience it is necessary to pay: it is necessary to rebuild the excretory system. After all, the kidneys of amphibians differ little from fish and are designed to remove excess water from the body. The problem of removing the final toxic product of protein metabolism - urea - is solved very simply: it is simply dissolved in a water flow, which is so constantly "flowing through the body." But starting life in the "land scaffle" Kidney "must be replaced by" kidney of savings "designed to withdraw external environment As much water as possible. At the same time, it is necessary to change the final product of protein metabolism from the urea to less toxic urinary acid, and this requires additional energy costs. Another important problem is dry, devoid of glands. The skin creates great difficulties with thermoregulation - and in lifetime on land, where there are no sharp temperature differences, it is not necessary to neglect.
As for the terromores, then acquiring an improved breathing apparatus and covered with a dense leathery of the eggs, they retain the skin inherited from amphibians - soft wet, penetrated by the glands. It leaves many opportunities for further development, closed for plagors. Skin glands can eventually develop into something useful in new conditions. You can turn them into the hairs that are tactile functions, and making these hairs sufficiently thick, create heat insulating cover - wool. You can purchase an additional selection body - sweat glands, which are also a thermostat (sweat, evaporating, cools the surface of the body); You can change the composition of their discharge, turning these glands into the Milky, and feed with their help with their help. If it is extremely difficult for the placomorphs to the appearance of warm-bloodedness, then for the terromorphs, it is still asking himself. True, according to the degree of dependence on sources of water, animals are very much inferior to real reptiles and will dwell near the reservoirs.
In the Perm seas, the leading position captured cartilage fish
As you can see, each of the two development options has its advantages and its shortcomings. The entire three-hundred-year-old history of land vertebrates is the history of the contest of terromorphs with coarseraphs, where the evolutionary success was accompanied by one, then the other. Latest Paleozoic Terromorphs were more successful. Perm is the time of domination on land of beastly-shaped lizards.
Permian Park
In early Perm dominant predators were sfenacodonts. They achieved a length of 3-4 m, however, they did not differ in too much mobility, having short low-disordered limbs. Obviously, sphenacodonts from hungry death saved only that their prey was even less mobile. Perhaps some advantage over the victim provided elongated spine vertebral processes. They were attached to the muscles that had to bend the body when driving, and it is also possible to raise the front part of the body when attacking, because it was difficult to jump with such a structure. The same extended processes were intended for some of the sphenacodonts for fastening the leathery sails, as believed to serve for thermoregulation.
Common herbivores during this period were edafozavraProbably the first of the highest vertebrates adopted to plant food. The body of Edafosaur was large, long and barrel, but supported his short and weak limbs. So the maximum, for which it was enough, it is overwhelmed from one source of food to another. But he was the owner of a luxurious sail.
Sailing beasts ( pelicosaurs), and predatory, and herbivores, gradually go from the scene to the middle of Perm, displaced by more movable animals. Queen of the Late Perm Sushi has become foreigners. This largest animal relevant hormone was first discovered in 1898 by the Paleontologist Vladimir Prokhorovich Amalitsky, during the excavations on the shore Northern Dvina. The animal received his name in honor of the outstanding Russian natural scientist A. A. Alantieva, under the leadership of which Amalitsky passed the course of Geology of St. Petersburg University. The discoverer was lucky enough to discover two full skeletons of foreigners and many fragments. Later, the remains of foreigners were found also in the Orenburg region. This magnificent predator had an elongated, slightly flapped with sides, a powerful tail, a narrow and elongated skull with a length of 40 - 60 cm, fingers equipped with large claws. Famous full specimens of foreigners achieved in length 3-4 m, but at the disposal of paleontologists there are separate fragments of larger animals.
As it should be a beastly, foreigners did not have horny scales, a number of researchers believe that it was covered with wool. Judging by some features of the structure, the predator was semi-wheeled or, at least a headclocky lifestyle, but the device of the teeth says that the main mining of foreigners has served not fish, but large fat fourth four-legged. The fangs of the upper jaw, narrow, with the sawmill cutting front and rear edges, were very developed. With closed, they lay down in the gaunt-shaped deepening on the outside of the lower jaw (kind of sheath), and the ends almost reached the lower edge of the jaw. The protruding part of the fang reached a length of 15 cm and more. Large and powerful cutters with closed pasta were tightly closed, the lower cutters were part of the gaps between the upper, and the fangs of the lower jaw in the pit on the nose. The cloth teeth are weak, small and few, in the lower jaw they are missing and probably did not play a big role. As can be seen, all this formidable apparatus served mainly for the capture and dismemberment of production, but not for facing. In case of loss of fangs - the main tool to the attack - in the fanging bag of foreigners there was up to three replaceable teeth, which are in the infancy and capable of developing in a short time to a new functional fang. Judging because in Arkhangelsk region A variety of individual fangs of foreigners were found without any traces of damage or wear, the replacement of the fangs occurred regularly regardless of the presence or absence of damage.
The general appearance of foreigners resembled a terrible predator to a later era - saber-toothed tigers and, like them, she obviously mined meal, hunting animals with exclusively thick skin. The prey of the saber-toothed cats of Cenozoic was rhinos and hypopotamas, foreigners hunted on pareyazavrov and ditenoonts.
Pareyazaurs - A group of vegetative animals belonging to wastar lizards. They achieved a very large size (from 1.5 to 4 meters), but short and very massive limbs made a pairhazavrov very vigorous creatures. It was probably coastal animals that spent a lot of time in water like hippopots. In the skin of the back and head of these lizards, similar to convex plaques of ossification, which attached a skin surface uneven or buggy character.
Dicotenontsinclude a lot of species, a variety of appearance and lifestyle, but they are all phytophages (herbivore). Like foreigners, they belonged to the glorious community of terromores, but to less highly developed their group. The dimensions of these animals range from 30 cm to 4 m. For most ditenoonts, the disappearance of all teeth is characterized, except for the top of the upper fangs, but they were able to crush food in the mouth with the help of a horny coating of the deceine - their lower jaw could make the front-rear movements. In addition, their disposal had a horny beak, such as what can be seen from modern turtles.
However, not only the vertebral make up the earthly fauna and revive the surrounding landscape. Preceded by Perm carboxy (coal) period was the time of unprecedented insects. Late Paleozoa boasts some representatives of this class, not characteristic of any other era. Group megasecopters It originated at the end of the carbon, was very successful throughout the Perm period and died out without a trace on the border of Perm and Triassa. In its appearance, megasecopters resembled dragonfly, but unlike the latter they were not predators. Them rota apparatus It was a piercing-sucking. In length, these comara-dragonflies reached 10 cm and more. But do not hurry to come to horror, imagining a decade-catering blood blood. As believed, these very beautiful insects Pierced soaring fabrics Plants and eaten it with juice, disputes or seeds.
Well, who spoke about insects, you can not remember the detachment PalaeodictyopteraSubject to different systematics from 20 to 40 families. In Carbon, some of his representatives had the scope of the wings to half a meter. In Perm, they were somewhat crushed, but still their size is impressive. Like megasecopters, Palaeodictyoptera did not survive the great extinction.
As for the Perm seas, the leading positions in them captured cartilage fish. Then this subclass was somewhat more numerous and diverse than today and included a number of extinct units. Dominant maritime predators, like now, were sharks. However, modern sharks, although they are similar to Perm, are not their straight descendants. Perm sharks were extinctly extincted at the end of the Paleozoic era, similar biological design arose re-and independently in the middle of the mesozoic.
An important element of the Perm sea landscape was shaved formed by the colonies. brachiopodsimilar to modern oyster bolds. But Brachiopods (Plechenogi), although reminded by their appearance of bivalve mollusks, are not molluscs. They are a separate type of animal kingdom, once very numerous (up to 30 thousand species), and now with a total of 280 species. Many Brachiopod's Paleontologists become victims of great extinction. It turned out fatal and for four-beam corals - Main Rigors Perm. Also, a great extinction put a point in existence trilobitov, peculiar arthropods, known from the Cambrian and maintained some features in their structure ring worms. But actually, trilobites and for the Perm period were very rare animals, "living fossils." Their highest flourishing falls on the Silician period. Until the end of Paleozoa, she lived only one species, and all the specialists are about 10 thousand.
Marine inhabitants, safely survived the great Perm extinction were challenges - Ammonites and belemnita. These long-livers began to explore the oceans from the middle of the Paleozoic era and disappeared only at the very end of the Mesozoic.
Mesozoic Zigzag
Just over 250 million years ago the number of species living on Earth began to decline rapidly. Large predators and beasts disappeared, gigantic insects, fierce Perm sharks. Then the variety of species begins to grow again, but now the earth fauna has a completely different appearance. The dominant position in it, both on land and the sea, occupy real reptiles (plagamorphs).
At the beginning of the Mesozoic, some lizards whose ancestors spent so much effort in order to break with the water medium, the secondally returned to the water lifestyle. It is they who occupy a niche, liberated by extinct Perm sharks, and become dominant maritime predators.
"At a distance from the coast above the sea, one rose alone, and then another head, sitting on long neck; The heads were flat, like a snake, and the neck was silent gracefully. It seemed that two huge black swans were floating, whose torso slightly climbed over the water. " - So academician Vladimir Afanasyevich Obruchev described the meeting of the heroes of his science fiction novel "Plutonia" with the marine lizards of Plesiosaurov, known from the Triassic period.
Someone from the great paleontologists outlined exterior appearance These lizards are less poetically, but more brightly "Snake, Throwing through the seal." However, among the Plesiosaurov, species possessing a short neck and long (up to 3 m) skull are known. Worthy competition of plesiosaurs as marine predators was ichthyozavra (fishing), creatures with a common appearance resembling dolphins, but the mouth, more similar to the crocodile. In length they could reach up to 24 m.
As for land animals, the great extinction of large beasts seems to have experienced only some ditenoids, and they did not survive until the middle of the mesozoic. In Triassa, the most successful group of land animals become arhozavra. Under this name, they imply a special branch of reptile development, in the end, led to the emergence of crocodiles, birds (on the interpretation of some biologists - especially advanced highly specialized reptiles adapted for flight) and the beauty and pride of the Mesozoic era - dinosaurs. From other reptiles, Arhozavrov was more perfect respiratory system and more effective system blood circulation, lightweight skull, as well as a special design of the limbs, which allowed some species with time to move to two-legged walking, which in turn allows you to develop quite most speed, moving on land. At the same time, Arhozavra, being crumbs, consume significantly less water than the beasts and, appropriately, significantly less dependent on its sources. They do not need water to isolate protein exchange products, since they remove urinary acid, and not urea. The skin of the arcosaur, devoid of glands and covered with horny scales, does not evaporate water.
In TRIAS, it was among the arhozavrov that the speciation went faster, and very soon they took the dominant position. Their triumphal procession continued in the following: Jurassic and chalome, periods. And then another extinction and descendants of the terromorphs survived by the Perm-Triassic catastrophe of terromorphs, small and unbelieving, thoroughly thoroughly had a pity existence throughout the Mesozoic, revenge. They became the hedlers of a completely new class of vertebrate - mammals, almost everywhere who did the dominant position in the Cenozoic Era.
Who is the killer?
An unprecedented ecological disaster that had a place on the border of Perm and Triass tried to explain to the collision of the land with an asteroid and began to look for a suitable crater or debris. Virtually no avail. True, in Antarctica managed to detect something, it seems like the traces of the fall of large heavenly Body, but these certificates (small fragments and grains of quartz, possibly shock origin) are unworthy of unconvincing. Meanwhile, in the 70s of the XIX century. It was done scientific discoveryApparently, having a much closer attitude towards the question of interest to us than Antarctic finds.
In 1873 - 1875, Russian researcher Alexander Lavrentievich Chekanovsky took a number of expeditions to study the interfold of Lena and Yenisei. During these expeditions, he collected about 4 thousand samples. fossil Flora and fauna, 900 copies of modern plants and 18 thousand - insects and vertebrates, among which turned out to be many new, to that unknown science of species. However, the scientist himself repeatedly emphasized: "The main subject of my classes was the study of geological." Among them, he highlighted the "opening of an unknown to the region of the erupted rocks, so significant that it surpasses all the other, somewhere a well-known similar kind." We are talking about the so-called siberian Trappakhdiscovered by Chekanovsky on huge spaces for the flow Lower Tunguso And north of her to the River Olenek.
Trapps are very picturesque basalt formations resembling cyclopic steps. Hence the name (from the Swedish word, meaning the "staircase"). They originated as a result of volcanic activity of extraordinary intensity, compared to which all eruptions that took place on the memory of mankind, including Krakatau and Santarina explosions, just Christmas flaps. The molten magma was poured onto the earth's surface not with individual craters, but through multi-kilometer faults, pouring huge spaces. Then the magma froze, forming solid basalt arrays, much less susceptible erosion than the surrounding sedimentary rocks. After a long weatheraction, flat rock terraces appeared, which we observe these days.
Such entities are known not only in Siberia, but the Siberian Province, which is about 4 million square meters. km, and thickness up to 4 km, is the most extensive in the world. She left far behind the second sizes in the Indian Dean Plateau. As it turned out, the outpouring of Siberian trappers occurred approximately 252 million years ago, that is, it is well linked in time with the beginning of the Perm extinction. It is logical to assume that these two events are related to each other, but at first this version has faced serious difficulties, and almost was not rejected.
It should be understood that the whole mass of the molten basalt, which we observe now in the frozen form, did not break out onto the surface in one, not a wonderful day, destroying everything alive in a solid flaming stream. The Siberian Trapping Province is the result of increased volcanic activity, stretching somewhere on a million years. Every single outpouring was only a local catastrophe and the fiery rivers flowed into Siberia, on the lands, later modern Europe And Africa, continued to peacefully rely the huge dragonflies and hunt foreigners. On a planetary scale, it looked as if a giant coal oven appeared in one of the corner of the earth, which had gradually, and did not pass one hundred thousand years before her activity had significantly affected the general condition of the biosphere.
Geophysics took the clarification of physical and chemical characteristics Substances participating in this process. Knowing these characteristics, it is possible to simulate the process of formation of trappers using equations describing the behavior of heterogeneous viscous environments, and calculate the mass of gas and volatile substances that are released during gases. The model was created, and paleontologists comprehended disappointment. Everyworth out that Siberian trappes are not suitable for the role of murderers. Its distinguished during their occurrence of carbon dioxide and poisoning substances was clearly not enough to cause such a global cataclysm. Great Perm dying began to seek another explanation, but then the model that existed earlier was revised.
Actually, and without binding to Perm extinction, the old model left some ambiguities. Classic trapping magmatism looks like this. Somewhere in the depths of the Earth for the unknown, the reasons arises a grandiose ascending stream of superheated mantle substance - the so-called mantle plume . As the mantle substance is raised, it is heated and expanded, its density decreases, forming a huge bubble. At the same time, the pressure of the plume on the lithosphere should lead to an increase earth crust. This is happening before the main phase of the trapping magmatism, that is, earlier than the molten magma will begin to break into the earth's bark and on its surface. Calculations have shown that in the case of the Siberian Siberian province, a letter of about 2 km was to form a height of about 2 km, but no signs of such processes were found in those parts.
In 2011, an international group of scientists, including many Russians, published in the journal Nature. The article, convincingly explaining this fact. Based on a detailed chemical analysis of samples of Siberian basalts, the authors concluded that in Magma, from which Siberian trappes were formed, there was a significant (10-20%) admixture of recycled rocks of the oceanic bark. Obviously, the plot of terrestrial crust, plunged deep into the mantle and was then pushed back to the revealed plume back, and the ocean bark differs significantly from typical mantle breeds in its composition and density. It is heavier and contains more volatile substances that can be released when heated. The model, developed on the basis of new data, shows that no raising the earth's surface should have been, because the top of a mantle pluma due to the impurity of the oceanic cortex breeds had a higher density and the plume did not raise a lithosphere, like a monstrous bubble, and gradually "acted "It is from the bottom of erosion, which occurred in the contact zone of the molten substance of the top of a plume with solid rocks components bottom layer Lithosphere). As a result, for several hundred millennium, plums "Run" the way to the lower layers of the earth's crust, located at a depth of about 50 km.
The same model assumes a largest largest, compared with the previous emission of CO 2, HCl and other substances that can change the ecological situation into the atmosphere. In addition, in the case of falling into a plum of oceanic cortex, the emission of volcanic gases will leak much more rapidly. The majority should break into the atmosphere at the very beginning of the process, even before the molten magma rose to a depth of 50 km. For the time segment of order hundreds of thousands of years, such a "stove" could well change the biosphere, so since the publication of this work, the involvement of Siberian trappings to a great extinction has little doubt.
More space for the discussion leaves the question of the nature of changes provoked by volcanic activity. The fact that the catastrophe rapidly affected the marine fauna, suggests the change in the chemical composition of water in the world ocean, most likely, a significant increase in its acidity caused by the release of chloride hydrochloride (hydrochloric acid). Changes occurred in the ground fauna suggests climate change towards greater aridity (aridness), which could be caused by a greenhouse effect from the release of volcanic carbon dioxide. The area of \u200b\u200bthe desert on the planet has greatly increased, the wet ranges decreased, which is why they survived and left the offspring, first of all, those species that were initially adapted to life under water deficiency conditions.
However, a number of paleontologists denies the Aridity of the Perm climate compared to the Triassic Aridity. In this case, the change in the animal kingdom can be explained somewhat differently. The role of the greenhouse effect could be relatively minor, and the case was not so much in the amount of water, but in its quality. Then the most accumulation of acidity that ruined the overwhelming majority marine organismsturned out to be destructive and for those land animals whose life cycle It was somehow connected with reservoirs. This explains the death of the mass of insects and the loss of their positions by the class of amphibians, and the disappearance of the moisture-loving animals of the lizards. And dressed in their "land safes" reptiles amniotes were much less sensitive to this kind of oscillations, therefore they got a predominance.
Whatever it was, the giant trapping outpouring is only part of the explanation. It is not possible to not only establish how specifically there were their direct impact on the Perm organisms, but also to trace the entire chain, irreversibly violating the balance of the biosphere. In general, the work is a bad edge. By the way, taking into account the rates caused by volcanic processes of change, it is easy to imagine that there is a reasonable force on the planet, armed with powerful technical knowledge, and the catastrophe would be avoided. Imagine that such a violating environmental equilibrium factor is not at all anthropogenic origin begins to act now. Moreover, in its pace and scales, it approximately corresponds to the Siberian traffic outpouring. At first, humanity may be concerned about only the help of directly affected by the elements, but sooner or later they will begin to finance the development to predict the further development of events. Well, let the creation of a reliable model and the complete awareness of what is happening will leave, say, a hundred years. Another hundred years to find the means to adjust the process. Well, two hundred years (you see, what are we unjudging) to embody the recommendations "in the gland". Total four hundred years. And the trapping magmatism to become for the Fatal Planet, consisted of hundreds of thousands of years. So, we have a great time. Of course, provided that technical and scientific knowledge enjoy sufficient respect in society.
One of the most catastrophic extinction in the history of the Earth, which occurred in the Perm period, on geological standards continued literally an instant. How the American scientists calculated, the destruction of 96%water and 70% of ground the species took only 60 thousand years.
Perm landscape. Reconstruction of Victor Leshyk.
Perm extortion is not in vain called great - nothing like that in the history of our planet has not happened since then. But, despite the grand scale of this catastrophe, scientists have not yet come to a common opinion about its causes. To date, there are three hypotheses that explain the mass extinction of living organisms - the fall of the asteroid, the global eruption of volcanoes and the cascade of ecological cataclysms imposed on each other.
Trying to deal with the events distant from our days by 250 million years, researchers of the Massachusetts Technological Institute measured the duration of the disaster in time. As it turned out, the extinction took place "almost instantly from a geological point of view" and continued about 60 thousand years, that is, at least 10 times faster than previously thought. To get this stunning digit, scientists succeeded due to new, more accurate methods for determining the age of rock.
"We have an idea of \u200b\u200bthe exact age and duration of extinction," said Professor of the Geological Faculty of Mit Sam Bowering. - But how could I kill 96% of all the inhabitants of the oceans for any tens of thousands of years? It seems that exceptional extinction requires an exceptional explanation. "
Approximately 10 thousand years before the catastrophe of the oceans of the Earth were exposed to a large amount of carbon's lung isotopes. As a result, the water was strongly acidified, and its temperature rose at once with 10 degrees. It was these events that destroyed most marine inhabitants, researchers are confident.
The most popular hypothesis of the Perm dieting mechanisms today connects it with Siberian trappiers - multilayer lavva fields arising from the most powerful volcanic processes that have thrown over the surface of the Earth more than five million cubic kilometers of lava.
"It is clear that the reasons that led to the extinction had to act very quickly," said the lead author of the study, graduate student MIT Set Burgess. - So quickly that most of the representatives of the plant and animal worlds simply did not have time to adapt to them. " The short-term intake events confirms the dominant hypothesis, according to which the volatile chemical compounds thrown by volcanoes radically changed the composition of the atmosphere and oceans, causeing the mass death of living beings.
Perhaps quotes Bauering The Daily Mail, even one catastrophic impulse of magmatic activity became a trigger that launched almost instantaneous collapse of all global ecosystems.
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