There are many different theories of the creation of the world and its development. And they are similar only in one thing: dinosaurs really existed. And this can be confirmed by a number of evidence. However, until now, no one can say with certainty why the dinosaurs became extinct. There are only a number of hypotheses explaining the possible reasons for the extinction of an entire population of these creatures.

Dinosaurs are classified as terrestrial vertebrates that lived in the Mesozoic era until the very end of the Cretaceous period. Their ancestors are considered to be reptiles, which are similar in structure to modern lizards. The appearance of dinosaurs on Earth is considered the result of a mutation of reptiles due to climate change.

Based on this and other knowledge about dinosaurs, various hypotheses began to emerge as to why they disappeared.

asteroid impact

This hypothesis is based on the assumption that at the end of the Mesozoic era a huge asteroid fell to Earth. The dust that rose after the fall did not settle for a long time. The rays of the sun scattered in it, which led to cold weather and almost complete darkness. Absence sunlight significantly slowed down or completely stopped processes important for the inhabitants of the planet (for example, photosynthesis).

Most plants and animals died out or were rebuilt to new living conditions. And dinosaurs were no exception. A complete restructuring of the entire marine and terrestrial range began. Clay layers found in all corners of the world, in which platinum elements, including iridium, significantly predominate, confirm this version. This substance is rarely found in the earth's crust, but it is an integral part of meteorites.

Glaciers

One of the reasons for the extinction of dinosaurs is considered to be the onset of the ice age. The cooling occurred at the end of the Cretaceous period, but many scientists tend to believe that this phenomenon was observed much later. Not a single form of life that existed at that time was ready for such sharp climatic changes.

There is no clear answer to the question of what influenced the movement of glaciers. And if we compare the chronology of this event with the biblical texts, we can assume that instead of glaciers there was a massive flood.

Volcanic activity

This version is rather the reason explaining the onset of the ice age and, as a result, the extinction of dinosaurs.

It is assumed that at the end of the Cretaceous period, most volcanoes on Earth began to show excessive activity. This led to shifts in the earth's crust. Volcanic dust and ash have affected the change in temperature. But such a process was supposed to take place not spontaneously, but gradually, so all the giant lizards could not die.

Natural selection

AT modern world no one is surprised by the statements that many species of plants and animals are on the verge of extinction. Everyone is well aware that this is mainly influenced by anthropogenic factors.

However, it can be assumed that the dinosaurs were killed not climate change, and the neighboring population. It is only in R. Kipling's "The Jungle Book" that animals say to each other: "You and I are of the same blood." In life, the strongest population survives - this is the essence of natural selection.

Epidemic

Based on the theory of evolution of Charles Darwin, bacteria and microbes appeared before all other forms of life on Earth. The processes of evolution did not bypass them, and these microorganisms mutated. Thanks to such statements, a new hypothesis was born about why the giant lizards died out.

Every living organism adapts to changing conditions. environment, however, not all inhabitants of the Earth can live with different bacteria on the principles of mutualism (“mutually beneficial cohabitation”). Therefore, the version that the dinosaurs were killed by an epidemic has the right to life. It is possible that most of the epidemics that at one time destroyed a huge number of people millions of years ago destroyed the dinosaurs.

The proof of this theory can only be knowledge of certain properties of microorganisms. The fact is that bacteria survive under a variety of environmental conditions. In severe frosts, they do not die, but only fold into a cyst. This shell allows microbes to live for a huge number of years in the so-called sleep mode. As soon as the conditions again become suitable for the life of microorganisms, they “wake up” and begin to multiply.

Hunger

One of the most unfounded versions of the death of dinosaurs is the lack of food. There is a theory that the resources on the planet will someday not be enough for everyone, and this will lead to the end of the world. Such assumptions, though easy to prove by simple calculations, but they concern the future.

It can be assumed that the dinosaurs survived all the climate changes, but the plants that they ate did not survive. But this only explains the death of herbivorous mammals. Where, then, did the lizard predators go?

Change in the force of gravity of the Earth

One of the most recent versions says that giant lizards have disappeared due to an increase in the Earth's gravity. The theory is based on the fact that the planets gradually increase in size. This means that their mass and attractive force also increase. Such a circumstance could well have affected the mobility of dinosaurs, as well as other creatures.

To understand why this happens, we can recall an example of such a phenomenon as complete weightlessness in open space on ships. That is, the lower the force of attraction, the easier it is to move. The weight of the dinosaurs was too great, and their body could really not be able to adapt to such changes. Every day it became harder and harder for them to move, which made it much more difficult to find food and their life processes in general.

Are dinosaurs still alive?

While some scientists are puzzling over the reasons for the extinction of dinosaurs, others put forward hypotheses that these creatures did not become extinct at all, and find confirmation of this!

Such hypotheses were initially based on the fact that some legends of different peoples are confirmed. And many legends spoke of magical creatures - dragons, which people began to destroy in ancient times. They found their salvation in caves and rocks located very far from human settlements. All descriptions of magical creatures are similar to those of dinosaurs.

At the moment, more and more information appears about chupacabra and other strange creatures that live in the mountains, forests and under water. And there is already a lot of evidence of their existence. For example, the Nessie monster that lives in Loch Ness.

A life form similar to the Loch Ness monster was seen in the Jökulsau-au-Dal River (Iceland) and in Lake Windervin (England). Eyewitnesses claim that the monster looks like prehistoric reptiles, it has a huge body and a long neck and has fins. The first mention of this creature is in the records of the Roman legionnaires, who at that time fought with the Celts. It is possible that the monster is a direct descendant of dinosaurs.

In 1915, the German submarine I-28 blew up the English steamship Iberia. In the logbook, the sailors noted that the ship sank too quickly and exploded at a depth of 1,000 meters. The wreckage of the ship floated to the surface of the water. Among them, the crew saw a strange creature that looked like a crocodile with four flippers.

The length of the sea monster was about 20 meters. This fact drew the attention of cryptozoologists. After a thorough study of the issue, they concluded that, most likely, the monster is none other than the mosasaurus, which is considered extinct for a long time.

But the clearest evidence that not all dinosaurs died is the tuatara. It is often confused with the common lizard. However, scientists have proven that this is not a descendant of one of the dinosaur species, but a real three-eyed dinosaur.

Dinosaurs are terrestrial vertebrates that lived on Earth during the Mesozoic era. They first appeared between 247 and 240 million years ago. Dinosaurs lived on Earth for about 175 million years.

It is believed that the last dinosaurs died out about 65 million years ago. This is the end of the Cretaceous period - the last period of the Mesozoic era. There are various theories as to why this happened.

Theories of the extinction of dinosaurs have been the subject of much debate. Scientists have not yet come to a consensus.

Huge asteroid

One of the popular theories, which is supported by a large number of scientists, is the theory that a huge asteroid (or group of asteroids) crashed into the Earth near the Gulf of Mexico.

The asteroid was so huge that the dust and debris that rose into the air as a result of its fall blocked the Earth from sunlight. Mountains formed at the site of the asteroid impact. The tsunami covered plants and animals under thick piles of rubble. The planet cooled and remained so for many years. On Earth actually changed climatic conditions and most animal and plant species became extinct.

A deadly chain of events ensued. Plants died without sun. Without plants, herbivores died. Without herbivores, predators died.

There is one problem with this theory, which can reduce all its plausibility to nothing. Paleontologists have not found dinosaur skeletons in the rocks dating back to the period of the asteroid impact. Some evidence even indicates that all dinosaurs died before the asteroid hit Earth.

Volcanoes

There is one more scientific theory regarding volcanoes. Scientists have found plenty of evidence that even before the asteroid hit, life on Earth was already in trouble.

Multiple volcanic eruptions emitted molten rock and corrosive gases. They could acidify the oceans. All this could have created an imbalance in the ecosystem long before the asteroid hit.

When dinosaurs lived on Earth, the climate was most likely hot and humid. No evidence of an ice age or glaciation was found in the rocks from this period. Carbon dioxide was close to current levels.

The ice caps at the North and South Poles have melted, causing sea levels to rise. Australia broke away from Antarctica and gradually moved away from the South Pole, closer to the equator.

The landscape was dominated by coniferous trees and ferns, and the first flowering plants appeared. About half of Australia was covered by shallow inland seas.

These data were obtained as a result archaeological sites in the fossils found in the rocks of this region. They contain marine mollusks and large prehistoric reptiles such as ichthyosaurs and plesiosaurs. Today this area is called the Great Artesian Basin.

But what happened to the climate during this period? Between the Early and Middle Cretaceous, the climate on Earth warmed by as much as 10°C. Some scientists have linked this stage of global warming to the huge impact of asteroids. Others attribute this to the large number of volcanic eruptions in the area that is today India and Pakistan.

The Late Cretaceous saw many great changes. Continents collapsed, volcanoes threw ash and gas into the atmosphere, rapidly changing the climate. Wind and ocean currents have changed. Sea levels have dropped. Marine changes, combined with volcanic action, may have caused mass extinctions.

Other theories

Some scientists believe that mass diseases and epidemics (such as plague) became the reason for the extinction of dinosaurs. As a result, entire populations of dinosaurs disappeared.

There are theories about the influence of space - a burst of gamma radiation damaged ozone layer Earth, and this led to irreversible consequences in the climate and the development of creatures.

There is also a theory about the influence of flowering plants. As a result of the spread of flowering plants on Earth, dinosaurs were poisoned by them, since such plants contain alkaloids (these are important active substances in plants).

There are a lot of theories about the extinction of dinosaurs, some seem more plausible, and some even fantastic.

Why dinosaurs became extinct

Dinosaurs, safely extinct about 65 million years ago, were creepy creatures - thick-skinned, armored, solid teeth and claws. For example, the tyrannosaurus rex, the largest land predator of all time, could easily bite a rhinoceros or an elephant in half with one elusive movement of its terrible jaws. And the weight of herbivorous lizards with columnar legs reached 30 and even 50 tons. And it is no coincidence that paleontologists, having unearthed the heavy bones of another antediluvian reptile, called it a seismosaurus, that is, a lizard that shakes the earth. The length of this monster, according to cautious estimates of scientists, was 48-50 meters.

For nearly two hundred million years, magnificent reptiles have been the sovereign masters of all three elements: nimble ichthyosaurs, reminiscent of modern dolphins, swam in the primitive seas, multi-ton diplodocuses walked on the ground, and toothy pterodactyls looked out for prey in the sky. (By the way, the wingspan of these flying monsters could sometimes reach 16 meters, which is quite comparable to the dimensions of a combat fighter today.)

Tyrannosaurus rex skull

And then, suddenly, giant lizards began to rapidly die out, they were replaced by nondescript, small and unremarkable creatures, leading a predominantly nocturnal lifestyle. Scientists knew about the sudden and catastrophic changes in the composition of the planetary biota at the end of the Cretaceous period already in the 18th century, and since then this mysterious phenomenon is often called the "Great Dying".

What happened? Usually textbooks paint such a simple picture. A large and prosperous group of reptiles (both predatory and herbivorous), which inhabited all the ecological niches of the planet, suddenly died suddenly - instantly and everywhere. And since these giants did not have serious competitors at that time (mammals huddled in the backyard of evolution and subsequently simply occupied an empty house), it is logical to look for some external reason. For example, a climatic cataclysm (a sharp cooling or, conversely, warming), a supernova explosion accompanied by deadly fluctuations in the gamma background, or a change in magnetic poles that temporarily deprived the planet of its protective shell.

For some time now, the asteroid hypothesis has become very popular. Say, at the end of the Cretaceous period, a huge meteorite crashed into the Earth, throwing billions of tons of dust into the stratosphere, which shielded the surface of the planet, which led to the death of green plants, and after them, the rest of the fauna. In addition, the fall of such a meteorite could provoke a revival of terrestrial volcanism, which noticeably aggravated the situation. It should be noted that serious paleontologists do not particularly support this point of view.

Where did the asteroid hypothesis come from? In the mid-1960s, in geological deposits dating from the boundary of the Cretaceous and Cenozoic (about 67 million years ago), scientists discovered a layer of blue clay with an anomalously high content rare metal iridium (20 times more than the average in the earth's crust). Subsequently, many similar anomalies were found (in some of them, the concentration of iridium exceeded the background by 120 times), and all of them turned out to be the same age - they lay on the border of the Cretaceous and Cenozoic.

Since there is very little iridium in the earth's crust, and in meteorite matter (primarily in iron meteorites, which are considered fragments of planetary nuclei) it is found in excess, the American physicist Alvarez associated the iridium anomaly with the fall of an asteroid. He estimated its diameter at 10-12 kilometers and even indicated the place of the disaster - the Yucatan Peninsula, where he managed to find an impressive crater about 150 kilometers in diameter.

The fall of such an asteroid would greatly shake our planet: a tsunami wave of monstrous strength and height would devastate the coasts tens and hundreds of kilometers deep, and a grandiose dust cloud would eclipse the sun for a long time. A six-month absence of sunlight would have killed green plants (the processes of photosynthesis would have stopped), and then (along the food chains) animals, both land and sea.

Since Alvarez put forward his impact hypothesis in 1980 (from the English. impact- "blow"), a lot of time has passed. To date, several dozen iridium anomalies are already known, and in geological deposits of very different ages, but it is not possible to connect them with the mass death of flora and fauna. Moreover, geologists have at their disposal a number of craters much more impressive than the notorious Yucatan. The diameter of some of them reaches 300 kilometers, but absolutely nothing serious has happened to the planetary biota (and this has been established reliably). Which is quite natural, because the biosphere is by no means a children's designer, the elements of which can be shuffled and put together at random, but a stable homeostat that can effectively resist various kinds of disturbances.

The famous Russian paleontologist K. Yu. Eskov notes:

In this sense, the situation with the Eltanin asteroid (about 4 km in diameter), which fell in the late Pliocene, about 2.5 million years ago, on the shelf between South America and Antarctica; the remnants of the asteroid were recently raised from a crater formed on the seafloor. The consequences of this fall look quite catastrophic: kilometer-long tsunamis threw the marine fauna inland; it was then that very strange fauna burials with a mixture of marine and land forms appeared on the Andean coast, and purely marine diatoms suddenly appeared in Antarctic lakes. As for the remote, evolutionarily significant consequences, they simply did not exist (the traces of this impact are contained within one stratigraphic zone), i.e. absolutely no extinctions followed all these terrible perturbations.

Thus, the picture is very interesting. As soon as iridium anomalies began to be purposefully searched, it immediately became clear that their rigid connection to the mass death of dinosaurs (or any other organisms) was nothing more than an illusion. The fossil remains of the Mesozoic lizards unequivocally testify: the catastrophic scenario of the Meltian Paleogene extinction is no good, since some groups of dinosaurs disappeared long before the iridium anomaly, while others sank into oblivion much later. The process dragged on for hundreds of thousands and millions of years, so there can be no talk of any swiftness.

Therefore, the asteroid hypothesis, as well as all other "impact" scenarios, can be sent to the archive with peace of mind, since they involve the simultaneous destruction of flora and fauna. Meanwhile, even the mass death of marine organisms at the end of the Cretaceous (much more hasty than the extinction of dinosaurs) was instantaneous only by geological standards and stretched out for a fair period - according to various estimates, from 10 to 100 thousand years. As for reptiles, they did not become extinct overnight.

K. Yu. Eskov writes:

How so?! And it's very simple: the extinction of dinosaurs has been going on throughout the Late Cretaceous at a more or less constant rate, but starting from a certain moment, this decline ceases to be compensated by the emergence of new species; old species die out - and new ones do not appear to replace them, and so on until the complete destruction of the group. (An analogy: the country is losing the war not because the enemy began to inflict unprecedentedly high losses on the front, but for another reason - tank and aircraft factories stopped in the rear due to lack of raw materials.) In other words, at the end of the Cretaceous, there was a non-catastrophic extinction dinosaurs, but the non-appearance of new ones to replace them (this, you see, noticeably changes the picture). This means that we can talk about a fairly long natural process.

No more persuasive alternative versions- for example, the hypothesis of a sudden change in magnetic poles or a supernova explosion near solar system. Of course, the magnetic polarity reversal is a very unpleasant thing, since the streams of high-energy charged particles flying from the Sun deviate in the lines of force magnetic field, forming the onion scales of the radiation belts. If, however, its thick magnetic “fur coat” is torn off our planet, then hard radiation will freely reach the surface of the Earth.

But, firstly, the leapfrog of the magnetic poles is by no means an exotic, but a natural periodic process, and the data of special studies, as a rule, do not reveal a relationship between global biospheric crises and changes in terrestrial magnetism. And secondly, the biosphere as a whole is an impeccably debugged homeostat that easily resists any outside interference.

A supernova explosion is a cataclysm on a galactic scale. If such an event occurs in the vicinity of the solar system (according to astronomers, this happens once every 50-100 million years), then the X-ray and gamma-ray fluxes will not only destroy the ozone layer, but also sweep away part of the earth's atmosphere, provoking the so-called "highlands effect", which not all organisms can survive. However, even in this case, the extinction will most likely not be sudden, but will stretch over tens and hundreds of millennia. In addition, hard radiation and the effect of high mountains should primarily affect the population of land and shallow water, but in reality, as we know, the situation was exactly the opposite: the flora and fauna of the open sea suffered the most, including microscopic ones, and of the inhabitants of the land For some reason, only dinosaurs became victims of the Great Dying.

This amazing selectivity is generally the most vulnerable point of all impact hypotheses: indeed, why did dinosaurs become extinct, while crocodiles survived and survived safely to this day? It is possible that the unprecedented popularity of various kinds of "impact" versions is mainly due to the success of observational astronomy over the past 20–30 years.

As soon as we are engaged in debunking idle myths, it is necessary to say a few words about the fauna of the Mesozoic. In almost any textbook, you can read that the Mesozoic era was the era of dinosaurs, and the Cenozoic era is the age of mammals that came to replace them. Meanwhile, this is a typical scientific prejudice.

Few people know that mammals were contemporaries of dinosaurs (they appeared on Earth almost simultaneously - at the end of the Triassic) and successfully coexisted with them for 120 million years. Moreover, if you sort through the bones of the fossil remains of all Mesozoic creatures, it turns out that the number of mammal species significantly exceeded the number of dinosaur species. True, our distant ancestors, vaguely reminiscent of South American possums, were at that time small and timid creatures, leading a predominantly nocturnal lifestyle.

With certain reservations, the very term “Great Dying” itself can be called a near-scientific myth. And if we are talking about the scale, then the Permian-Triassic extinction should have been called great - a grandiose biospheric cataclysm that happened at the turn of the Paleozoic and Mesozoic. In general, it was the largest in the history of our planet: if at the end of the Cretaceous about a quarter of families went into oblivion, then during the Permian-Triassic extinction, 50% of families, 70% of genera and 90% of species disappeared from the face of the Earth. In addition, all marine ecosystems have changed radically. It would be worth noting that all attempts to link the Late Permian crisis with the asteroid impact ended in absolute collapse - no traces of the impact were found in the corresponding horizons.

So, what was the reason for the extinction of the dinosaurs? One of two things: either climatic changes at the turn of the Cretaceous and Cenozoic, or purely “natural” causes - a radical restructuring within ecosystems and a change in communities.

Let's figure it out in order. We are used to the fact that the planetary climate is distinguished by a pronounced latitudinal zonality: tropical rainforests grow on the equator, savannas lie periodically moistened to the south and north of them, where countless herds of ungulates graze, and even further to the north and south stretches a strip of deserts scorched by the sun and semi-deserts. The subtropics give way to temperate forests - deciduous and coniferous, and they gradually give way to the cold tundra, where almost nothing grows. Well, eternal frost and eternal ice reign at the poles.

But it was not always so. The Mesozoic is a classic example of a thermoera, when there was no latitudinal zonality, and the global climate resembled the current subtropical Mediterranean type. It was warm and quite comfortable at high latitudes and even at the pole, but at the same time it was not too hot at the equator. In short, the temperature gradient - both seasonal and daily - was barely perceptible. But at the end of the Cretaceous, the thermoera was replaced by a cryoera with a latitudinal temperature difference.

Dinosaurs were cold-blooded (poikilothermic) animals. Unable to regulate their body temperature "from the inside", they were completely dependent on their habitat, but in the even climate of the Mesozoic, this did not cause them much trouble. If there is an abundance of heat outside, and impressive dimensions do not allow to cool during the night (most dinosaurs were large creatures), then maintaining a high body temperature will not be difficult. And all this without any participation of their own metabolism, for which mammals spend 90% of the energy they consume with food.

This curious phenomenon is called inertial homoiothermy (warm-bloodedness), and many scientists believe that thanks to this valuable quality, the dinosaurs became the rulers of the Mesozoic. And when the climate changed radically at the end of the Cretaceous, the giant lizards disappeared.

It would seem that we have found the answer, but again something does not converge. Why did dinosaurs die out, while other reptiles - also cold-blooded - continue to exist to this day? Why did the Cretaceous crisis affect mainly marine life, while land creatures survived it calmly? Why did some groups of dinosaurs begin to actively die out long before the fateful calendar date, while others slowly lived out their lives in the Paleogene?

Perhaps it makes sense to look for the answer elsewhere - in the structure of ecosystems? Let us remind the reader about nondescript Mesozoic mammals that lived side by side with pangolins for 120 million years without intersecting with them. These small insectivorous creatures, similar to modern possums or hedgehogs, occupied their ecological niche, which no one encroached on. But in the Cretaceous period, the situation changed radically.

K. Yu. Eskov describes these events as follows: evolution spurred on the sluggish metabolism of primitive mammals and made a "phytophage in a small size class" on this new metabolic basis. (Herbivorous dinosaurs were very large animals.) And if a small phytophage appeared, then a predator will certainly arise, which will not be limited to hunting for close relatives, but will grab everyone who can afford it. Therefore, a baby dinosaur - a small defenseless lizard that does not have inertial homeothermy - will instantly become a tasty prey for such a round-the-clock active predator.

The version is undoubtedly interesting, but it does not answer all the tricky questions. And here we are help will come genetics, understood in broad sense this word. Let's talk about marginality as the antipode of narrow specialization, because organic world develops in this way.

Once again, let us recall the Mesozoic mammals, who voluntarily ceded the world to magnificent reptiles and vegetate on the sidelines of evolution. Huddling in back corners, they were the real marginals, since they occupied those few ecological niches that the ruling class ignored with magnificent casualness.

The food base of herbivorous dinosaurs was gymnosperms and ferns, which were widespread as far back as the Devonian. Angiosperms, or flowering, flora, which appeared at the beginning of the Cretaceous period, were forced to settle in the backyards, since the gymnosperms dominated. Thus, flowering plants were just as marginalized as the small Mesozoic mammals. They had no choice but to occupy empty lands where there were no established communities of gymnosperms: landslides, burnt areas, river banks, that is, biotopes that are commonly called “disturbed”. And the species themselves, settling in such conditions, biologists call "coenophobic", that is, they are afraid of communities, preferring to exist separately.

However, the tactical loss ultimately turned into an important strategic advantage. Firstly, the flowering plants that settled on the “bad” lands no longer allowed gymnosperms there, and secondly, they had a flower, which played decisive role in the struggle for existence. If the gymnosperms for the reproduction of their own kind entirely relied on the wind, which passively carried their pollen, and therefore were forced to settle in a heap, then the flowering plants actively attracted insects, which increased their viability by an order of magnitude.

The existence of flowering plants did not depend on the elements, and angiosperms could afford the luxury of living in scattered wastelands. In addition, a new type of flora has learned to form herbaceous forms that not only effectively resist erosion, but also quickly capture free land.

The change of plant communities turned into a real disaster. Contrary to popular belief, not only dinosaurs died out, but also 25% of the Mesozoic families of invertebrates - cephalopods and bivalves, unicellular radiolarians, diatoms, foraminifers and other representatives of planktonic organisms. Their calcium shells formed grandiose deposits, which is why this period of the geological record was called the Cretaceous.

So inconspicuous yesterday's outcasts - flowering plants and mammals - crushed the dominant fauna and flora of the Mesozoic.

The onset of flowering plants today is commonly called the great angiospermization (from lat. angiospermae- "angiosperms"). When the new type of flora began to decisively predominate, what happened is what always happens when the foundation is destroyed: the building simply collapsed. After all, the kingdom of plants is exactly the foundation on which the floors of herbivorous animals and predators stand, and they are interconnected not only by food chains, but also by more complex relationships.

Dinosaurs tried to adapt to a new diet - they had beaks and powerful tooth batteries for grinding highly abrasive food. However, it did not work out well for them, especially in cereal pasture systems, where they obviously lost to ungulates. In addition, herbaceous forms of flowering plants form a turf that reduces erosion and organic runoff into fresh water and the oceans, which dealt a severe blow to marine invertebrate communities.

The thing is that the vast majority of the creatures that inhabited the planet in the late Cretaceous, advanced too far along the path of narrow specialization. For the time being, this gave them excellent chances of survival, but every advantage sooner or later turns into a disadvantage. Attachment to the communities of gymnosperms eventually played a cruel joke with the lizards: when the flowering ones went on the offensive, taking one territory after another from the former owners of life, the mammals easily joined the newly formed communities. But the dinosaurs could not do this and ended up in an evolutionary dead end, since their adaptive resources were wasted long ago. And for marginal mammals, such a turn of events was only at hand. Having experienced an explosion of speciation under new conditions, they populated the entire planet.

Of course, not only such large taxa as a class of animals or a type of plants can be marginal. Separate biological species, too, as a rule, do not sin with complete uniformity for the entire set of features. Moreover, the higher the genetic diversity of a species or population, the greater its adaptive potential. Such a community will almost always find a way to prolong its existence in the changed conditions. And even with a stable and measured life, intraspecific marginals can play an important role.

For example, winged individuals are occasionally found in populations of wingless water striders. There are very few of them - only 4%. They have genetic differences, but at the same time they can interbreed with their wingless companions and produce offspring. It turned out that these flying geeks are able to migrate over fairly long distances, thus ensuring genetic continuity between the water strider population of all water bodies. Four percent of the marginalized for this task is more than enough.

I must say that almost every biological species has, just in case, such an emergency reserve in the form of a rare genotype or an unusual form that allows you to survive difficult times. Let us repeat once again: the genetic diversity of a species or population is the key to its evolutionary success, so the marginals should be treated not only with respect, but also with care.

So, the emergence and wide distribution of flowering plants at the end of the Early Cretaceous (about 30 million years before the death of dinosaurs) not only radically changed the structure of continental communities, but also killed the Mesozoic pangolins that lost their plasticity, hopelessly stuck in dead ends of evolution. Of course, climatic perturbations could also play a role, but the key event, the starting point, was almost certainly this very fact - the onset of angiosperms.

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Ornithischian DINOSAURS The ornithischian dinosaurs are scientifically called Ornithischia. The shape of their pelvis is such that the bones of the legs are directed downward, parallel to each other. All of them were herbivorous and in the era of the spread of these dinosaurs - in the Jurassic and Cretaceous periods (202-65

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Lizard DINOSAURS Lizard dinosaurs (Saurischia), which appeared earlier than another group, had a pelvic structure similar to other reptiles. The two bones of their legs diverged in different directions. Some of them were herbivores, others were carnivores. They often

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Why did dinosaurs become extinct? According to the theory that currently has the largest number of supporters, an asteroid with a diameter of about 10 kilometers fell to Earth 65 million years ago. Even the place of its fall has been established - the Yucatan Peninsula in Mexico. The energy released

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DINOSAURS - AMAZING AND TERRIBLE LIZARDS The ancestors of these dinosaurs were "early reptiles" - thecodonts, which also gave rise to crocodiles, flying dinosaurs and birds. They were small, the size of a rooster or a little more, agile pangolins that lived at the end of the Paleozoic and at the beginning

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Dinosaurs take over the air The modern world is teeming with flying creatures - insects, birds, bats; there are others who, although not real flyers, are no longer quite terrestrial inhabitants - tree frogs, squirrels, woolly wings, lizards - “flying dragons”.

For more than 15 years at the University of Tübingen, one of the oldest educational institutions Germany, there is a Children's University, where the most inquisitive can get answers to any difficult questions from real professors. So that as many children as possible know what they are studying modern science, scientists published their lectures in the form of books. Now they are also in Russian. If your child is 7-8 years old and older and is interested in volcanoes, dinosaurs or knights' castles, these books are just a godsend. This time - about dinosaurs for children.

At the beginning of the Mesozoic era, our Earth looked completely different from what it is now. In those days, there was only one continent on the planet - Pangea, washed by a giant ocean. On this palm-and-fern-covered supercontinent, about 243 million years ago, new creatures appeared - small reptiles that dexterously moved on two limbs. We call them dinosaurs.

Dinosaurs looked very different: some wore shells, others wore thorns, others had horns, and others had long protrusions on the spine that resembled a sail. Some dinosaurs walked on two legs, others on four. Some ate meat, others ate plants, and others were omnivores.

About 150 million years ago, these hardy lizards, perfectly adapted to the conditions of their habitat, were the real masters of our planet. And it seemed that nothing threatened them ...

Brachiosaurus was as tall as a bell tower and weighed as much as twenty elephants. The Supersaurus was over 30 meters long, which is the height of a 10-story building. The ground shook under the footsteps of this monster. He seemed to have no one and nothing to be afraid of. Tyrannosaurus was a real monster: a head the size of a calf, in the mouth - sharp, long, inwardly curved teeth. The Tyrannosaurus rex had the strongest muscles, even the best runner in the world could not compare with it in speed. None of the modern animals, whether it be a tiger, a lion or an elephant, would not have the slightest chance to cope with it. But who then managed to defeat him?

And yet the fact remains: dinosaurs ceased to exist. During the Late Cretaceous, many millions of years before humans appeared, the dinosaur population began to decline, and about 65 million years ago they completely disappeared.

Many scientists and adventurers went in search of dinosaurs. In the past century, expeditions have scoured the jungles and other impenetrable places on the planet in the hope of finding at least one surviving fossil monster. But none of these attempts were successful. But the remains of dinosaurs were found in a variety of places. So, according to the American paleontologist Peter Dodson, only 3,000 almost complete dinosaur skeletons are stored in US museums. And none of them are younger than 65 million years.

It would seem that dinosaurs had no equal in the ability to survive, and they inhabited the planet for an incredibly long time. Nevertheless, at some point they gave way to another species, whose representatives formerly trembled with fear, barely seeing a dinosaur on their way. These cat-sized animals benefited when the dinosaurs died out. Apparently, their body was covered with fur, and they themselves resembled either squirrels or shrew mice.

Their cubs did not hatch from an egg, like dinosaurs, but appeared from the mother's womb, after which the mother fed them with milk. For this feature, scientists called them mammals (mammal is an obsolete name for milk) and identified them as a separate class of animals, to which man also belongs.

Why did these small, easily vulnerable animals spread all over the planet, while strong, powerful dinosaurs, on the contrary, died out? To answer this question, you must first remember that the extinction of certain species is completely normal and even useful. Everyone who is at least a little familiar with the history of life on Earth understands that modern animal species did not always live on it: they arose in the process of evolution and someday may disappear. As, for example, it happened with mammoths about ten thousand years ago.

And they are just one of many extinct species. Some species die out, not having lasted even a couple of million years, others live on Earth for hundreds of millions. Species leave to make room for others.

In the modern world, humans are primarily responsible for the extinction of species. People hunt, trade in rare animals or plants, destroy their habitat. Every hour three species of plants or animals disappear on the planet; accordingly, every month the Earth irrevocably loses more than 2,000 species.

What animals were on Earth at the time of the dinosaurs?

Apparently, four billion years ago, our entire planet was completely covered by the ocean. It was in it that the first living organisms originated. They were tiny bacteria, green algae and fungi.

And only after many millions of years did small fish appear in the sea. In the Mesozoic era, when dinosaurs were already walking on land, the sea still remained more populated, fish of all shapes and sizes frolicked in it: some were huge like a truck, others had spines growing on their fins, others were chained in a shell. And even then sharks plowed the ocean.

However, in the Mesozoic era, the land was also inhabited by a wide variety of animal species. But she didn't look the same as she does now. There were no five continents familiar to us, but there was a single giant supercontinent, which scientists called Pangea. Just then, in the Mesozoic, Pangea began to slowly split into two continents: the northern - Gondwana and the southern - Laurasia.

Most of the animals of that era died out, but we know of their numerous descendants. Even before the advent of dinosaurs, the first beetles and bugs were already crawling on the ground, centipedes reached two meters in length, and dragonflies could boast of wings that were not inferior in size to eagles. Among the few creatures whose appearance has not changed to this day are representatives of the cockroach squad, one of the most successful animals in the entire history of life on Earth (this is hardly surprising to someone who happened to encounter them in an apartment), because they have existed for more than 300 million years.

Of course, at the beginning of the Mesozoic era, when dinosaurs dominated the planet, nothing foreshadowed that it was cockroaches that would prevail in evolution. A career counselor, if there had been such a thing in those days, would have advised many species to retrain as reptiles, that is, reptiles. After all, it was in front of them at that time that a brilliant future opened up.

For millions of years, amphibians - that is, those who could live both on land and in water - evolved into reptiles, the first vertebrates that no longer needed water. They had a strong skeleton and laid their eggs on land. The first of them were relatively small, fed on insects and lived in old stumps. But they began to grow rapidly.

To get a little idea of ​​what the dinosaurs looked like, you can look at the crocodile: the same big mouth, strong chewing muscles, sharp teeth, powerful tail. Nevertheless, crocodiles are not descendants of dinosaurs: they both descended from the same group of reptiles - archosaurs.

Archosaurs were among the first to try to live on land. Pretty soon, there were a few rebels among them, early mammals that began to evolve in a completely different direction. But at that moment, no one would have been able to say what it would lead to.

We owe our knowledge of ancient animals, and especially of dinosaurs, to professional scientists and amateurs who, over the past 200 years, have discovered many remains of extinct organisms.

Although we are used to talking about the bones of dinosaurs that were dug out of the ground, strictly speaking, these are no longer bones, but stones. But why did animal bones become stones?

The corpses of animals quickly became prey: predators attacked their meat first, then worms and bacteria took over. Therefore, from soft tissues, whether internal organs, brain or skin, soon there was nothing left.

Even bones and teeth sooner or later begin to decompose in the sun. Although, of course, they are much harder and more durable than other parts of the body, and it will take bacteria much longer to destroy them.

But if the bones of a dinosaur fell into the river and ended up under a layer of silt, there they were inaccessible to bacteria and thus survived to this day. Gradually, water began to penetrate into the smallest pores of the bones, filling them with minerals, which were formed from salts dissolved in water. Thanks to these substances, over millions of years, the bones turned into stones or, as scientists would say, fossils.

Sometimes paleontologists specifically examine the soil in the place where in prehistoric times there was a riverbed. After all, it is there that you can find dinosaur skeletons.

How do scientists manage to determine with great accuracy how many millions of years this or that fossil is? Actually it's not that difficult. Quite a lot of waste accumulates on Earth: sand dust, lava, plant remains, and animal skeletons. The garbage of the whole planet settles in the form of layers of sediments.

The deposits of each such layer have their own characteristic features. Imagine that in hundreds of years, scientists will arrange excavations on the site of modern America. At some point, they will certainly begin to find a lot of cans of Coca-Cola and CDs. If there is also a dollar with an engraved date nearby, then it will be possible to conclude: if the same Coca-Cola tin is found elsewhere on Earth, then the entire layer in which it was found most likely belongs to the 20th century. That is, once having established the age of this or that layer on any part of the planet, scientists know what time the same layer belongs to in any other place on the Earth.

By studying the remains of plants and animals, scientists will learn how our planet looked like in prehistoric eras, what was the climate then: cold or warm, wet or dry, and whether summer and winter differed greatly. Sometimes they can determine with a great degree of accuracy what the weather was like in a given period, even if it was millions of years ago. The thing is that both animals and plants are perfectly adapted to their habitat, and their remains can tell us a lot about the then nature.

For example, if there are corals in some ancient layer of the earth, then we can say that at the time when the layer was formed, the water was warm enough, because corals can only live in warm water.

So paleontologists have established that there were periods on Earth when the level of carbon dioxide in the air was significantly higher than today. Carbon dioxide is released during combustion, and its levels in the atmosphere are now of great concern to environmentalists. Environmentalists fear that carbon emissions from cars and power plants could make the world too warm.

But in reality, everything is not so simple. After all, thanks to paleontologists, we know that during the Cretaceous period, air saturation carbon dioxide(carbon dioxide) was higher than in our era. Dinosaurs, by the way, only benefited from this. Since plants need carbon dioxide to grow, ferns, conifers, and cycads (a group of ancient plants that looked like palm trees) in those days reached enormous sizes. And with them the dinosaurs grew up.

Why did dinosaurs get so huge?

The first dinosaurs were relatively small, no larger than a brown bear. Unlike their ancestors, slow amphibians, they could move fast enough, even the shell with thorns did not bother them very much. They owed their mobility primarily to the structure of the body: their paws were located not on the side of the body, but under it (this distinguishes dinosaurs from other reptiles). They moved on their hind limbs and were mostly carnivorous - feeding on reptiles, amphibians and mammals.

By the time dinosaurs appeared on Earth, mammals had already settled very well on it. Due to their wooly coat and the ability to maintain a constant body temperature, they were well adapted to the rather cool climate of the next ice age.

But with the beginning of the Mesozoic, the Earth became warmer. At this time, the giant Pangea had already begun to slowly break into pieces and the warm waters of the ocean rushed into the continent. The ice caps at both poles began to melt, the rains became more frequent, and the temperature crept up. On average, during that period it was six degrees warmer than today.

These changes were to the taste of cold-blooded reptiles. After all, the speed of their movement directly depends on the ambient temperature - in the cold they are extremely slow. In addition, with a large amount of solar energy, reptiles no longer need such abundant food as mammals. Those constantly need food to maintain their body temperature; the body of mammals can be compared to a stove into which firewood must be thrown every now and then so that the fire does not die out.

Of course, this is not the only reason why mammals in the Mesozoic era had to give way to reptiles, but it was one of the most significant.

Among reptiles, dinosaurs have benefited the most from warming. The number of slow turtles, lizards and crocodiles that moved on four legs did not increase much. At the same time, the active bipedal lizards quickly consolidated their positions.

True, their development was also not uniform. So, for example, the first carnivorous dinosaurs lacked food for food, they devoured each other and eventually almost completely died out. Only those that switched to plant-based food survived.

To grind food in the stomach, they learned to swallow a couple of stones with food every time, since they still did not know how to chew. And only one of the last dinosaurs acquired massive teeth to grind tough leaves.

The necks of dinosaurs began to lengthen and grow until these giant lizards could easily reach the trees and eat the foliage directly from them. During the Jurassic period, the temperature on the entire planet increased, the vegetation became more lush, which means that the dinosaurs also became more obese.

New species of dinosaurs such as Apatosaurus, Brachiosaurus and Ultrasaurs spread all over the planet. In order not to remain hungry, dinosaurs were forced to absorb food for twenty hours a day. If they got hot, they went to swim. And from time to time they dozed off, warming themselves in the sun.

As far as species diversity is concerned, dinosaurs truly had no equal. By 2018, about 1000 genera and about 1200 species are already known. It is believed that the total diversity could reach more than 1500 genera and 2100 species! Scientists divided these diverse animals into two orders - lizard-hipped and ornithischian, differing primarily in the structure of the pelvis.

Thanks to the efforts of paleontologists, a large number of dinosaur eggs have been found. They are about the size of a soccer ball and quite strong, so the cubs had to work hard with their beak to hatch.

In many nests, many eggs lying nearby were found. This suggested that dinosaurs hatched eggs like birds, and then, like birds, diligently and patiently took care of their offspring. This, by the way, is one of the evidence that dinosaurs were quite advanced creatures.

How bigger size reached herbivorous dinosaurs, the more interesting they were for their other brethren. So gradually formed a new group dinosaurs that returned to eating meat. And they became more dangerous than all the dinosaurs that lived before them.

These new predators launched a hunt for herbivorous dinosaurs. The largest and most prominent of these was the Tyrannosaurus Rex. Presumably in size, it was comparable to a one-story house and weighed no less than an elephant. Tyrannosaurus rex had a giant skull and a small brain. Its front paws were extremely small and, most likely, were hardly used. The situation with the teeth was completely different: curved, with small notches, and one could prick a whole rabbit on each.

Reptiles lived not only on land, but also in water and even in the air. Ichthyosaurs, similar to giant dolphins, plowed the sea. Powerful pterosaurs flew through the air - their skin resembled that of bats.

How these giant animals learned to fly, we can only guess. Perhaps the once most courageous of them climbed a tree or a rock and jumped from there like squirrels. Only the lightest or those with feathers on their paws and torso managed to survive. And then they passed on the ability to fly to their descendants.

The rest were less fortunate.

Dinosaurs ruled the world of our planet for 130 million years - 100 times longer than the human race has existed on Earth. Dinosaurs became extinct 65 million years ago. But 65 million years ago, not only dinosaurs had a bad time. Then, in general, hard times came on Earth. Life on the planet was in mortal danger. Flying reptiles are gone. Aquatic reptiles died out in the oceans, as did clams and starfish. Even most of the small animals - plankton - died out.

Why did dinosaurs become extinct?

Nobody knows for sure. But there are a lot of theories. Most of them suggest that there have been some strong changes in the climate of our planet that have damaged many living organisms, not just dinosaurs. The latest and most popular theory claims that dinosaurs and other animal species became extinct due to one terrible universal catastrophe: 65 million years ago, the Earth collided with an asteroid, and at the same time there was a terrible explosion.

Interesting fact: apart from dinosaurs, 65 million years ago, flying reptiles and big number sea ​​inhabitants.

Examining clay deposits in layers of the earth's crust dated as deposited 65 million years ago, scientists found a large content of iridium in these rocks. Iridium is rarely found on Earth, since during the formation of our planet, iridium, as a heavy element, plunged deep underground and is mainly located near the earth's core. Iridium comes to Earth only from space, when meteorites and asteroids fall from the sky. Scientists have found iridium in ancient clayey deposits all over the world. Here is their conclusion: iridium fell out of a cloud of dust that was thrown into the atmosphere when an asteroid collided with Earth. Here's what could happen.

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The largest dinosaurs

Dinosaur Extinction Hypothesis

An asteroid with a diameter of 10 or more kilometers flew from space into the Earth's atmosphere at a speed of at least 100,000 kilometers per hour. Crashing into the Earth, he formed a crater with a diameter of 160 kilometers. Tons of crushed rocks and soil (a mixture of asteroid and Earth rocks) from the explosion flew high into the sky. From the passage of a fireball through the atmosphere and an explosion in the atmosphere, hurricanes arose, which carried the dust that shot up into the sky throughout the Earth. The sky was covered with a huge dust cloud. The sun faded and the day became night. The darkness continued for months. The average daily temperature dropped from plus 19 to minus 10 degrees Celsius. The mass death of plants and animals caught in the darkness and cold began.

Following herbivores, predators that fed on herbivores began to die out. In the end, the cloud descended to the ground, leaving a memory of itself in the form of a large admixture of iridium. Many scientists, however, are skeptical about this theory. Why, then, they ask, did birds, crocodiles, turtles, snakes, and most mammals survive, as well as insects, mollusks, ocean fish, and many plants. This theory is also doubtful because the extinction of dinosaurs occurred very slowly - over millions of years, and not during one giant cataclysm.