Dina Beltyukova
Research work "Why dinosaurs became extinct"

1. Introduction…. 3

2. Main body

2.1. Life dinosaurs on planet earth…3

2.2. Main Extinction Hypotheses dinosaurs.... 4

3. Conclusion…. 5

4. List of used literature…. 6

Introduction

I very often hear that it is necessary to protect nature, the animals that live on Earth, but in order to protect nature, you need to know the history of the planet, the animals that lived on it, and some of them somehow disappeared. For example, dinosaurs.I am very interested in the question: why did they die? It would be funny if Diplodocus looked through our window, what would we do? And then I decided to do research, armed himself with encyclopedias and asked his mother to find information on the Internet.

my goal research work is to identify the causes of extinction dinosaurs.To achieve the goal, it was necessary to perform the following tasks:

1. Learn about life dinosaurs.

2. Consider how they looked dinosaurs.

3. Study what they ate dinosaurs.

4. Design an album "Causes of extinction dinosaurs»

An object research: life dinosaurs.

Item research: causes of extinction dinosaurs.

Methods work: acquaintance with television films, reading encyclopedias, viewing articles on the Internet.

Hypothesis: I think there are several versions of extinction dinosaurs.

Life dinosaurs on planet earth

Greek word « dinosaur» means "terrible lizard". The English zoologist Richard Owen called these animals terrible. Probably the first huge bones found dinosaurs made a terrible impression on the scientist. Still would! Legs twice the height of a man, teeth the size of a palm, skulls the size of a small car.

But not all dinosaurs were huge. Dwarfs also lived next to the giants. Small meals dinosaurs needed a little. That's why "dwarfs" could live in any conditions.

Dinosaursthere were several types: predatory and herbivorous giants, flying and marine reptiles. The teeth of predators were like sharp daggers, while those of herbivores were small and flat. Biggest dinosaur is Ultrasaurus. If they lived today, they would probably easily step over the train. Ancient lizards also inhabited the seas. The largest marine reptile was the Stretosaurus. His jaw reached a length of three meters.

Main Extinction Hypotheses dinosaurs

Dinosaurs are extinct 65 million years ago. Long before the first man appeared. Something incomprehensible has happened. In just a few thousand years died out predatory and herbivorous giants, flying and marine reptiles. Together with them, many underwater and terrestrial plants disappeared. Only insects, fish, crocodiles, turtles and small mammals remained on the planet. Until now, it is not known exactly what happened then on Earth.

There are about two dozen causes of extinction dinosaurs.Here are the main ones:

1. The fall of a giant meteorite. Upon impact, a mass of dust rose into the atmosphere. The atmosphere was not transparent to sunlight for many years. In the ensuing darkness and cold, almost all plants died. And after the plants from hunger and cold - all dinosaurs.

2. The death of huge lizards came from space, but the culprit of their death was not a meteorite, but a beam "hard" radiation that our planet has crossed.

3. The constant movement of continents and seas has led to significant climate change. Warm conditions without any temperature fluctuations gave way to colder nights and harsher winters.

Tropical vegetation has disappeared. Dinosaurs were forced to roam, move to the equator in search of food, water, warmth.

4. Could destroy dinosaurs volcanic explosions and earthquakes. Or the first mammals to eat all the eggs of ancient reptiles. Although this theory is the most unlikely.

Conclusion

According to the results research workI made the following conclusions: it was global changes on our planet that caused the extinction of such unique creatures as dinosaurs. The movement of the continents, climate change and flora, meteorite, volcanic eruptions - all this played decisive role in fate dinosaurs. Thus, our hypothesis was confirmed.

Nevertheless, I believe that some relatives have survived to this day dinosaurs. And we all know them! These are crocodiles, lizards, snakes and others. And if we do not protect the environment, these species may disappear, as well as dinosaurs.

Introduction

Life on Earth arose about 3 billion years ago; it began with tiny single-celled creatures, and about 225 million years ago, dinosaurs appeared on Earth in the process of evolution. They inhabited the Earth for about 160 million years, i.e. over a period 50 times longer than the period from the appearance of man to the present day. Not all types of dinosaurs existed at the same time: some species died out, others arose.

Dinosaurs were well adapted to their environment. Some of them were herbivores, others were carnivores, so there was enough food for everyone. Dinosaurs had very strong skin, some species had huge massive bodies and long necks, while others were no larger than a turkey. Dinosaurs reproduced by laying eggs with a hard shell that protected the embryo well during development.

How did it happen that the dinosaurs that dominated the Earth for so long, suddenly disappeared 65 million years ago? Many people are interested in the answer to this question, therefore there are many hypotheses about the causes of the mass extinction of dinosaurs. We will look at some of them.

Searching for traces of the past

The first dinosaur bone was found by the English naturalist Robert Plot in 1677. At that time, no one had any idea that animals that differed from modern ones once existed on Earth. The discovery of the Raft was considered the bone of an old elephant or even some giant. The first documented traces of dinosaurs were discovered in 1802 in Connecticut (USA) by the peasant Plinyo Moody. On a stone slab found in his field, there were prints of three fingers, which were attributed to ... "the claws of a raven released from Noah's ark after the Flood."

The word "dinosaurs" was first used by Richard Owen on August 2, 1841. This term is derived from the Greek deinos - terrible and sauria - lizard, so dinosaur means "terrible lizard." After studying many fossil remains, Owen came to the conclusion that these animals had much in common with each other and had the largest sizes among all reptiles. Immediately, the first images of ancient monsters appeared, made on the basis of found fragments, and life-size sculptures of dinosaurs began to entertain visitors to large exhibitions.

From the middle of the XIX century. amateurs and professionals alike have searched for dinosaur remains all over the world. Violent passions flared up in the Far West of the USA between 1870 and 1890. Expeditions of two prominent American paleontologists Edward Cope and Othniel Marsh discovered huge cemeteries of dinosaurs in the Rocky Mountains (Canada). The most expensive expedition was organized by the Berlin Academy of Sciences to Tendaguru (Africa) in 1907. It cost 200 thousand German marks. Over one and a half thousand people discovered more than 250 tons of fossil remains in 3 years of work. In the course of their study, scientists came to the conclusion that among the lizards there were small, medium, large and simply huge lizards. The body length of dinosaurs ranged from 20 cm to 30 m. In total, there are currently about 1 thousand species of dinosaurs.

The earliest dinosaurs were land predators, then herbivores appeared. Some of them have gone to life in the water. Ancient dinosaurs were bisexual, but scientists still do not know for certain how males differed from females. It is assumed that in horned dinosaurs, males had longer and more massive horns that could be used as tournament weapons. Male duck-billed dinosaurs had a longer crest on their heads than females. It is even assumed that some forms, differing in morphological features and sizes and described as different species and genera, represent males and females belonging to the same species.

Dinosaur groups

By type of food, dinosaurs are divided into predators moving on two legs, herbivores and scavengers. They lived singly or in groups in both warm and cold climates. Some hunted, which required not only muscular, but also intellectual efforts. Anatomical features (massive hind limbs, huge body and rudimentary forelimbs) of giant predatory dinosaurs created serious problem: in the event of a fall, they were not able to get back on their feet, because. they could neither lean on their weak forelimbs, nor slip their hind legs under their heavy body.

The distribution of dinosaurs into groups does not depend on their size, mode of movement and food.

According to the structure of the pelvic bones, dinosaurs are divided into two groups: lizards (Saurischia) And ornithischian (ornitischia). The differences between them are as follows. The composition of the pelvis in four-legged animals includes three pairs of bones: pubic, iliac and ischial. In lizard dinosaurs, the ilium points upward where it joins the sacrum, the ischium points downward and backward, and the pubis points forward and downward. In ornithischian dinosaurs, the ischial and ilium bones are arranged in the same way, and the pubic bones have two branches directed in different directions: one forward and the other back, parallel to the ischial bones. The significance of these differences is not clear.

Differences between groups of dinosaurs in the structure of the jaws and teeth and related differences in nutrition are more easily explained. In lizard dinosaurs, the teeth were located along the edge of the jaw in one row, which reached the end of the muzzle. Each tooth of a conical or chisel shape sat in a separate cell. In ornithischian dinosaurs, a toothless predentary bone was located in the anterior part of the lower jaw, and the front teeth were often absent in the upper jaw. Many ornithischians had a horny beak, like turtles. In addition, the lateral teeth were pushed inward from the edge of the jaw, and their arrangement was multi-row. Such a displacement of the teeth is due to the fact that the cheeks were located outside the jaws. This made it possible to keep food in the mouth while chewing. Lizard dinosaurs did not chew.

All ornithischians were herbivorous and moved either on two or four legs. Among the lizards were both herbivores and predators, which, for the most part, were bipedal.

Like all archosaurs, dinosaurs had a diapsid type of skull with two, and not one, as in other reptiles, temporal cavities behind the eye sockets. This made the skull lighter, freed up space for the development of powerful jaw muscles, contributed to a more perfect action of the jaws when eating, and also contributed to the improvement of the auditory apparatus.

Another feature characteristic of dinosaurs was the structure of the pelvic girdle and the positioning of the limbs, which ensured greater mobility of animals. Unlike other archosaurs and most reptiles, the dinosaurs' hind legs were straight and moved in a vertical plane when walking, like birds and mammals. Most other reptiles (for example, crocodiles, lizards, turtles) have paws widely spaced to the sides. In the pelvic girdle, dinosaurs had a complex sacrum of five fused vertebrae and a perforated acetabulum, which included the head of the femur. These anatomical features made dinosaurs the most mobile of the Mesozoic land inhabitants.

A - a four-beam pelvis with free space below;
B - three-beam pelvis with pubic bones directed forward

One of the amazing features of some large herbivorous dinosaurs, both lizards (diplodocus, brachiosaurs) and ornithischians (stegosaurus, ankylosaurs), which was not available in any other animals, was the presence of a second brain (this was reflected in the generic name of one of them: "Diplodocus" in Greek means "dvudum"). The volume of the brain inside the fused sacral vertebrae of the pelvic girdle was 10–100 times the volume of the brain. The question arises, which brain, posterior or anterior, was the main one? It is believed that the hindbrain coordinated the work of the limbs, the anterior - food activity and sensory organs. This "decentralization" of brain functions, according to some researchers, was one of the reasons for the extinction of dinosaurs.

Hypotheses about the causes of the mass extinction of dinosaurs

From the Triassic to the Late Cretaceous, dinosaur diversity increased. It seemed that nothing foreshadowed their disappearance without a trace. But at the end of the Cretaceous period, the entire prosperous group of planetary hosts died out. Species extinction is a natural evolutionary process. It usually happens slowly, unevenly. But the speed with which the largest group of reptiles disappeared is amazing.

The hypotheses about how this happened can be divided into two groups:

– hypotheses explaining the extinction by external, including extraterrestrial, causes;
- hypotheses linking extinction with internal, biological factors.

Hypothesis 1

The first group includes the hypothesis that in the territory of India, in the Deccan region, lava oozed abundantly from a giant fault 400 km long, and there was unbearable heat. Volcanoes emitted huge amounts of carbon dioxide into the hot air. It was almost impossible to breathe such air. Clouds of ash and sulfur, escaping from the vents of volcanoes, rose high into the sky and enveloped the entire Earth. The atmosphere was poisoned by poisonous volcanic gases, and the soil by endless acid rain. Plants died from lack of light, followed by herbivorous animals, and then predators. The earth is getting colder. Then the ashes settled, and the cold was again replaced by heat. Carbon dioxide (at that time there was 10 times more of it in the atmosphere than today) created a "greenhouse effect". Heat was kept at the surface of the Earth, and the air began to heat up, rains became rare, lakes and swamps dried up, and many wet forests were replaced by deserts. The drying up of coastal shallow waters with their richest fauna and an increase in the overall salinity of the Ocean led to the extinction of 95% marine species animals. And then a new ash plume darkened the sky again, and the cold returned to the planet. Such sharp changes in climate continued for more than 600 thousand years. As a result, only less specialized species than dinosaurs survived, such as mammals.

Hypothesis 2

Another common version of the death of the Cretaceous giants is the fall of a huge meteorite near the village of Chicxulub (Mexican island of Yucatan). A meteorite that weighed thousands of billions of tons left behind a crater 200 km across! The power of the strike was comparable to the explosion of such a number of atomic bombs, which is 10 thousand times greater than the modern world stock. An air wave of monstrous power destroyed most of the terrestrial species of plants and animals, earthquakes swept across the planet, and giant tsunami waves circled the Earth several times.

This hypothesis appeared in 1970. Its actual justification is the evidence of the geological record: in many parts of the world, a small layer of clays with an unusually high content of elements of the platinum group, in particular iridium, rare in the earth's crust, but widespread in element meteorites. Such a layer is thought to have formed only if the deposits were "diluted" with large amounts of meteoric material. Assessing how much such a meteorite could weigh, scientists drew attention to the ancient crater near the village of Chicxulub. The time level of the layer coincides exactly with the time when the last dinosaurs disappeared, as well as other groups of terrestrial and marine animals and plants.

The dust that rose as a result of the explosion made the atmosphere almost opaque to sunlight for several years. The photosynthetic activity of green plants, which are the initial link in the food pyramid, has sharply decreased. Further, as in a chain, there was an extinction of various groups of marine and terrestrial organisms.

Hypothesis 3

It is believed that rapid climate change, which led to the mass extinction of species, could be caused by the drift of the continents and a change in the direction of winds and sea currents. On the continents, the change of seasons was sharply marked: the hot summer began to change cold winter when herbivorous dinosaurs were deprived of green fodder. Dinosaurs were unable to adapt to seasonal temperature changes. However, there are no facts confirming such a catastrophic acceleration of continental plate drift.

Location and directions of continental drift during the Cretaceous period

Hypothesis 4

In the middle of the Cretaceous period, the largest restructuring of the planet's vegetation cover in the history of the Earth took place: angiosperms (flowering) plants, grass appeared, and cereals became more widespread. For herbivorous animals that ate more primitive plants, when switching to a different diet, a significant restructuring of the entire enzymatic digestive system was required. It is possible, though highly doubtful, that they were unable to overcome this physiological conflict.

Hypothesis 5

Recently, scientists have put forward a new hypothesis for the extinction of dinosaurs - at least, some carnivorous species. Prehistoric lizards fell victim to a discrepancy between the energy needs of their gigantic organism and the objective possibilities of satisfying them. Specialists of the British Zoological Society link this version with the answer to the question why nature did not create, say, a lion or a tiger the size of an elephant. Such a huge carnivorous creature would not be able to hunt fast enough to replenish its energy needs in time, they say. According to scientists, evolution should eventually lead to the fact that carnivores weighing more than 1 ton, living on the surface of the Earth, will lose their right to exist due to energy deficiency. However, it is doubtful that this shortage occurred suddenly and led to the extinction of all dinosaurs in a historically short time.

Hypothesis 6

Perhaps the dinosaurs lost the fight for survival with new, rapidly emerging species of mammals and birds. However, this hypothesis lacks factual material to substantiate.

Hypothesis 7

As a result of any catastrophe on a planetary scale, the destruction of the ozone layer could occur, and ultraviolet rays could cause a sharp increase in the rate of mutations in organisms. It is possible that common parts of dinosaur genomes were unstable to such mutations, which led to the rapid extinction of all their species. Species with resistant genomes survived.

Conclusion

A meteorite near the village of Chicxulub and a powerful eruption in the Deccan are the main "suspects" in the case of the death of dinosaurs, which happened at the turn of the Cretaceous and Tertiary periods 65 million years ago. But for more than 20 years, scientists have not made a final "verdict". With renewed vigor, disputes broke out in March 2004, when Hertha Keller from Princeton University (USA) stated that she had evidence of the "innocence" of the meteorite. She claims that the Chicxulub stone crashed to Earth long before the death of the lizards.

In the sediments at the site of the famous crater, the fossilized remains of tiny marine animals that died out along with the dinosaurs were found. This layer appeared after the cosmic catastrophe, and it took about 300,000 years to form. According to G. Keller, one Deccan eruption would have been quite enough to destroy the dinosaurs, and the meteorite - Chicxulub or otherwise - could only be the last straw that overflowed the cup.

A supporter of the "meteorite" hypothesis, the Dutchman Ian Smith believes that Hertha Keller misinterpreted the results of samples taken in the crater. In his opinion, after the impact of the meteorite, the crash site was covered by a powerful tidal wave - a tsunami - and went under water, and it took only a few weeks for the formation of such a layer of sediments.

According to the geologist Vincent Courtillo, the death of the ancient lizards was not as catastrophic and fleeting as it is usually imagined. The latest fossils from that time show that the giant reptiles died out gradually - over hundreds of thousands of years. And this is difficult to explain with the help of the "meteorite" hypothesis. Over the past 260 million years, four mass extinctions of animals have occurred on Earth, and each time they were preceded by an unprecedented force of volcanic eruptions.

Not everyone agrees with this opinion. Geologist Eric Byufto believes that for each case of extinction of animals, you can quite pick up a suitable meteorite crater. Well, then, why should all such catastrophes on Earth have the same cause? Byufto does not argue with the fact that numerous species of animals died out regularly, and these dramas were not necessarily associated with abrupt catastrophic changes. However, the extinction of animals 65 million years ago was so massive that it is more correct to assume that

that it was caused by some powerful and fleeting impact, for example, the fall of a large meteorite. Well, besides, according to Byufto, it is hard to imagine that the dinosaurs that inhabited the entire Earth from the equator to the poles fell victim to sharp fluctuations in climate, but, for example, crocodiles calmly survived the turn of the Cretaceous and Tertiary periods.

So, the time for the final verdict is delayed. Scientists have yet to examine meteorite craters again and again, carefully study the fossils and, finally, find out why the crocodiles survived the dinosaurs after all ...

Literature

1. Laura Camburnac. Dinosaurs and other extinct animals. - M.: Makhaon, 2006. - 123 p.

3. Illustrative encyclopedia: dinosaurs / D. Burney; Artistic D. Sibbik; Per. from English. I.N. Alcheeva, N.N. Nepomniachtchi. - M .: AST Publishing House LLC: Astrel Publishing House LLC, 2002. - 222 p.: ill.

4. Relatives of dinosaurs / Per. from English. S. Freiberg. - M .: Astrel Publishing House LLC: AST Publishing House LLC, 2002. - 56 p.: ill. - (Secrets of wildlife).

5. Dinosaurs. The Complete Encyclopedia / Per. from English. M. Avdoni-noy. - M.: Publishing House of EKSMO-Press, 2000. - 256 p.

Dinosaurs are ancient creatures that appeared on the planet approximately 225 million years ago. For 160 million years, these animals dominated the planet. The extinction period took about 5 million years, and for about 65 million years they have been absent in the animal world. There are many hypotheses as to why the dinosaurs disappeared. How these animals died out and ceased to exist, we will tell in our article.

The advent of dinosaurs

Planet earth was inhabited different types plants and animals 3 billion years ago. In the process of evolution, plants and animals appear and disappear, and each such process has its own time interval and period. Dinosaurs on the planet lived in the Mesozoic era - these are the Triassic, Jurassic and Cretaceous periods.

The first simplest plants were seaweeds, and the first animals were small sea mollusks. The appearance of fish occurred about 500 million years ago. Approximately 370 million years ago, the first animals came to land - amphibians. Reptiles are a new group of animals that appeared about 300 million years ago. The animals had scaly skin, could lay eggs, and be permanently on land. Dinosaurs were next in the chain of evolution. An extinct animal species gave impetus to the development of such a science as paleontology.

Description of dinosaurs

One of the amazing animals that lived on the planet are dinosaurs. How these large animals died out and how they lived can only be judged by the fossilized remains. Fossils suggest that they were reptiles, like crocodiles, lizards, turtles and snakes. The size of dinosaurs varies widely - from tiny to giants. They had four limbs and a tail. Dinosaurs stood and moved on straight limbs, some on their hind legs, others on all four, and still others could move on both two and four limbs. Many dinosaurs had long necks and teeth. Their habitat was significant, but 65 thousand years ago they suddenly died out.

Dinosaurs are divided into two groups: lizards and ornithischians. The difference between the groups is in the structure of the pelvic bones. In lizard dinosaurs, the structure of the pelvis is four-rayed, and in ornithischians it is three-rayed. Some species of ornithischians had horns, spikes, shells.

Increasing interest in dinosaurs

In the 30s of the XIX century, the fossilized remains of dinosaurs were first discovered. Then archaeologists did not attach much importance to them, and only after some time it became clear that these fossils belong to ancient animals. The very concept of "dinosaur" was introduced by the English zoologist Richard Owen in the middle of the 19th century. WITH Latin"dinosaur" is translated as "terrible", "dangerous", "terrible", and from the ancient Greek language - "lizard", "lizard". Since then, interest in these animals has been constantly growing. How many years ago did dinosaurs become extinct? The answer to this question is given by the science of paleontology. Ancient animals are studied by scientists, filmed in films, they become heroes of books. And despite such interest, there is no exact answer to the question of why dinosaurs died out.

Age of Dinosaurs

At the end of the Permian period, a single continent, Pangea, was formed. characteristic feature this time there was global volcanic activity and the disappearance of about 90% of animals. Reptiles have adapted best to the new conditions. At the beginning of the Triassic, a group of reptiles called "Pelicosaurs" appeared. By the middle of the Triassic period, they were replaced by a group of reptiles called "therapsids". In parallel with the therapsids, a new group of reptiles, the archosaurs, developed. This group of reptiles is the ancestor of all dinosaurs, pliosaurs, crocodylomorphs, ichthyosaurs, placodonts, and pterosaurs. The next type of reptile was called thecodonts and was adapted to life on land. And dinosaurs have already developed from them. Extinct animals have adapted well and have taken dominant positions on land, in water and in the air.

During the Triassic period, the following Coelophysis, Mussaurus, and Procompsognatus existed. Plant dinosaurs developed and evolved.

The largest animals lived in the Jurassic period. In the late Jurassic period, land animals began to appear - brachiosaurus, diplodocus, etc.

In the Cretaceous period, predatory reptiles began to predominate in the seas and oceans. New types of dinosaurs appear.

End of an era

The Cretaceous period is the heyday of giant lizards, air pterodactels and marine reptiles. At the end of the Cretaceous, a split into Gondwana and Laurasia occurs. The climate on Earth becomes much colder, ice caps form at the poles. Insects appear and increase.

All this led to the extinction of many species of plants and animals, including dinosaurs. They did not die out overnight, but given that their dominance lasted 160 million years, their disappearance happened quite quickly. The causes of the catastrophe that occurred in the Cretaceous period are still not clear.

But are all dinosaurs extinct? The descendants of ancient reptiles are the crocodiles, lizards and birds that exist today. The first birds appeared in the Cretaceous, and by the end of the era they already had developed plumage. When the dinosaurs became extinct, birds took over the baton of evolution.

Astrophysical Extinction Hypotheses

The fall of an asteroid is one of the most common versions. The time of its fall coincides with the formation of the Chicxulub crater (Mexico). These events occurred about 65 million years ago, during the period when the dinosaurs died out. Perhaps the fall of the asteroid caused destructive actions, as a result of which there was a mass extinction of all life.

The multiple fall hypothesis states that the fall of the asteroid occurred several times. In addition to the Chicxulub crater, there is the Shiva crater in the Indian Ocean, which formed around the same time. This hypothesis explains why the extinction occurred gradually.

There is also a version of the explosion of a supernova and the collision of a comet with the Earth.

Geological and climatic extinction hypotheses

Significant changes took place on the planet during the period when the dinosaurs began to disappear. How animals died out is suggested by the theory of changes in average annual and seasonal temperatures. Large individuals need a warm and even climate. Volcanic activity could lead to a change in the composition of the atmosphere and cause a greenhouse effect. A large emission of volcanic ash could provoke a volcanic winter, thereby changing the illumination of the Earth. Significant sea level drop, ocean cooling, changes in seawater composition and surge magnetic field The lands also may have contributed to the extinction of the dinosaurs.

Evolutionary-biological hypotheses of extinction

One of the hypotheses of this group adheres to the situation of the emergence of a mass epidemic. It is possible that dinosaurs could not adapt to the changed vegetation, which led to poisoning. The probability of destruction of eggs and cubs by the first predatory mammals is high. There is also a version that females disappeared during the Ice Age. Scientists have proposed another version of the death of dinosaurs - suffocation: there was a sharp decrease in the amount of oxygen in the atmosphere.

Why did the dinosaurs disappear?

Why did the dinosaurs disappear? How these questions died out Answers to these questions give a variety of theories and hypotheses, but none of them fully answers all questions. It is known that the extinction of species began long before the moment of the catastrophe, and the astronomical hypothesis in this case is doubtful. Many theories lack factual data, such as the hypothesis of the regression of the World Ocean or changes in the magnetic field. Also, the lack of completeness of paleontological data can give a distorted picture.

Combining hypotheses forms a more illustrative picture. Hypotheses, complementing each other, provide answers to more questions, and the picture of that time looks more drawn and detailed.

The process of evolution - the extinction of the old and the formation of the new - is consistent. And the process of evolution of dinosaurs until the end of the Cretaceous period occurred naturally. But for some reason, at the end of the Cretaceous period, the old species died out, and the new ones did not appear, and, as a result, there was a complete extinction of this species.

From a paleontological point of view

The great extinction version is based on the following facts:

1. The emergence of flowering plants.
2. Gradual climate change caused by continental drift.

According to scientific world, the following pattern was observed. The developed root system of flowering plants, their better adaptability to soil quickly replaced other types of vegetation. Insects that fed on flowering plants began to appear, and insects that had previously appeared began to disappear.

The root system of flowering plants began to grow and interfere with the process. The surface of the land ceased to erode, and nutrient material ceased to flow into the oceans. This led to the impoverishment of the ocean and the death of algae, which, in turn, are producers of biomass in the ocean. In the water there was a violation of the ecosystem, which caused a mass extinction. It is believed that they are closely connected with the sea, so the chain of extinction has spread to them. On land, they tried to adapt to the green mass. Small mammals and small predators began to appear. This was a threat to the offspring of dinosaurs, since the eggs and cubs of dinosaurs became food for the appeared predators. As a result, conditions were created that were negative for the emergence of new species.

It ended, and with it, active tectonic, climatic and evolutionary activity also ended.

Children and dinosaurs

Interest in ancient animals is not only among adults, but also among children. Today the project "Why did the dinosaurs become extinct?" included in the kindergarten and elementary school curriculum. The uniqueness of such activities lies in the fact that the child independently develops, looking for answers to questions and gaining new knowledge. The question of why dinosaurs became extinct is as curious for children as it is for scientists. Interest is primarily due to the fact that these animals are not on earth today and the exact answer to the question of the reasons for their disappearance has not yet been received.

Millions of years ago, the Earth belonged to ancient giants - dinosaurs. They reigned for a long period and suddenly disappeared in a short period of time by historical standards. What were these animals? Why did dinosaurs become extinct?

Giants of Earth's distant past

The name "dinosaur" is translated as "terrible lizard". The honor of giving a name to the found remains of huge prehistoric animals belongs to the English paleontologist Richard Owen.

Ancient giants existed millions of years ago and inhabited the entire Earth, including the territory of modern Antarctica. In those distant times, it was part of a single continent along with India, Africa and Australia and had a warm climate. The most valuable find was found here - the remains of a lizard that lived millions of years ago. Why did the dinosaurs, which so densely populated the planet in ancient times, die out? What power could destroy all the giants without a trace? This is one of the mysteries of our time.

Getting Started with Dinosaurs

The bones of these animals were found in the period of the ancient world. Then it was believed that these were the remains of the great heroes of the Trojan War, which remained on the battlefield. In medieval Europe, there was a different point of view - the bones of dinosaurs were mistaken here for the skeletons of giants (the Bible mentions them) who died during the Flood. As for the eastern countries, according to their mythological ideas, they believed that these were the bones of the legendary dragons.

This continued until the middle of the 19th century, until scientists attempted to classify the gigantic remains found. And scientists from two European countries were the first to do this.

British and French contributions to the study of dinosaurs

English scientists were the first to undertake the hard work of describing and classifying the giants of the prehistoric world. Back in the 17th century, Oxford professor Plott first described the bone of a megalosaurus, which was then mistaken for the remains of a giant who died during the Flood. IN early XIX century, a great contribution to the study of dinosaurs was made by the outstanding French zoologist Georges Leopold Cuvier. He was the first to classify a fossil as a flying reptile and gave the name to the pterodactyl. After him, British scientists described the plesiosaur, mesosaurus and ichthyosaur.

A systematic study and description of the bones of prehistoric animals found by that time began in 1824 in England. Then were described and named Megalosaurus, Iguanodon, Hyleosaurus. In 1842, Owen noticed their similarities and differences from modern reptiles and singled them out into a separate suborder, giving them a common name - dinosaurs.

Now we already know a lot about the giants of antiquity, but so far one of them remains unanswered. important issues: Why did the dinosaurs become extinct?

The time of existence of terrible lizards is the Mesozoic era

To date, the remains of the most ancient dinosaurs are approximately 230 million years old. One of the earliest lizards is the staurikosaurus.

According to scientists, dinosaurs appeared in the late Triassic, reigned on Earth in the Jurassic period and suddenly disappeared at the end of the Cretaceous. This happened 65 million years ago. The era of the dinosaurs is the Mesozoic. It is characterized as a very interesting time in which many important events took place. First of all, this is the period of the dinosaurs that then reigned on the planet. But it was in the Mesozoic that modern flowering plants, birds and mammals - those that surround us now. In addition, this is a time of great changes in the face of the planet. First, in the Triassic period, the giant continent of Pangea split into Laurasia and Gondwana. Then the latter, in turn, split into modern Africa, South America, the Indian subcontinent, Australia and Antarctica.

At the end of the Cretaceous period, another important event occurs - the disappearance of the giant owners of the planet. Why did dinosaurs become extinct? This question has not received a definitive answer since then.

The era of dinosaurs - the Mesozoic - is characterized by a warm and mild climate. At that time there were no such temperature fluctuations as now. The climate throughout the planet was about the same. Animal world was varied.

Reptiles were widespread, the first mammals appeared. The heyday of the animal world of the planet falls on the Jurassic and Cretaceous periods. Jurassic dinosaurs are best known to modern man. At this time, huge reptiles appear, represented by a wide variety of species: flying, marine, terrestrial, herbivores and predators.

Types of dinosaurs - from small to large

The famous reptiles of antiquity trace their lineage back to the archosaurs. They appeared at the end of the Triassic period and quickly became the leading form of life. Now they are represented by modern crocodiles. Then, millions of years after the Permian mass extinction, the dinosaurs split off. There are several hypotheses about exactly where the terrible lizards first appeared. According to one of them, this happened in South America.

In the most famous period of dinosaurs - the Jurassic - these reptiles acquired gigantic proportions. Scientists have a huge number of types of giants of the prehistoric world - more than a thousand. They, in turn, are combined into 500 genera and are divided into two groups: lizards and ornithischians. In addition, they can be divided into herbivores (sauropods) and carnivores (theropods), as well as terrestrial, semi-terrestrial, aquatic, and flying.

The biggest

The greatest interest in modern man is caused by huge dinosaurs. Today it is difficult to imagine that once upon a time giants up to 20 meters high and up to 40 meters long roamed the Earth. The largest herbivore dinosaur is the seismosaurus. Its length reached 40 meters, and its weight approached 140 tons. Amphicelia is another herbivore giant. It is possible that its length was up to 60 meters. It is now impossible to prove this, since the only vertebra of this reptile was lost.

Dinosaur predators were also huge. For a long time, the Tyrannosaurus rex was considered the largest and most dangerous of them. According to the latest research, the giant laurels among the predators of the Mesozoic era passed to the spinosaurus. Growth is about 18 meters, huge long jaws, like a crocodile, and a weight of 14 tons - this is his appearance. However, the rest of the predatory dinosaurs were not much inferior to the spinosaurus and tyrannosaurus rex.

small and dangerous

Among the ancient reptiles there were individuals of modest size. Compsognathus is the smallest of the carnivorous dinosaurs. It weighed a little more than two kilograms, and the average length of an individual was 100 centimeters. Armed with sharp teeth and three long claws on its front legs, it posed a serious danger to small animals.

Heterodontosaurus is another representative of small dinosaurs. Scientists conditionally classify it as a herbivore, but the presence of fangs suggests that it was rather an omnivore.

As can be seen from the above, the types of dinosaurs were very diverse.

The mystery of the disappearance of dinosaurs

The mystery of the death of dinosaurs has been of interest not only to scientists for the second century. To date, it has been possible to establish the approximate time of their extinction, but one can only guess about its causes. There are a lot of hypotheses about what happened. Among them there are those with which most researchers of the world of dinosaurs agree, but there are also many completely fantastic assumptions.

First of all, it must be said that such mass extinctions of species have already happened in the history of our planet. Scientists count five such events, when up to 96% of all life on Earth disappeared.

Approximately 65-66 million years ago, at the end of the Cretaceous period, an unprecedented extinction of life occurs again. It is most famous for the reason that the dinosaurs that reigned on land and in the sea disappeared completely. For some reason, they were unable to adapt to the changed conditions. What has changed so much and what is the reason for the changes? Why did the ancient reptiles die out, but the mammals that already existed in the era of dinosaurs survived and began to reign on the planet?

Possible reasons for the Great Disappearance include:

• the fall of a huge meteorite or asteroid;
• epidemic;
• comet impact;
• increased volcanic activity, which led to the release of ash and a change in the Earth's illumination (temperature drop);
• a sharp change in the magnetic field of the planet;
• gamma burst;
• extermination of eggs and offspring of lizards by widespread predatory mammals;
• an experiment set over the animal and plant world of the Earth by an alien civilization.

This is only a small part of the versions of the death of dinosaurs. All of them have many shortcomings, and most of them have no actual evidence. None of these theories can explain the whole complex of events that took place.

Domestic scientists have put forward a biospheric version of the death of dinosaurs, which convincingly proves how this could happen. In their opinion, this happened due to two events: climate change and the emergence of flowering plants. The new kind vegetation replaced all the old forms.

New insects appeared, feeding on flowering plants, which led to the extinction of previous species. Sod appeared, which prevented soil erosion and leaching nutrients into the seas and oceans. As a result, they became impoverished, which killed most of the algae. This led to the extinction of marine life. Further along the food chain, flying lizards, closely associated with water bodies, began to die out. On land, dinosaur competitors were small predatory mammals destroying the offspring of giants. The cold snap and the constant struggle for survival further exacerbated the plight of the dinosaurs. Under such conditions, they lost their evolutionary advantage. The old species continued to exist for some time, but the new ones no longer appeared.

The main disadvantage of the biospheric version is the fact that almost nothing is known about the actual physiology of dinosaurs.

Where can you see dinosaurs?

Despite the fact that the terrible lizards disappeared millions of years ago, you can still see them now. To do this, you need to visit the dinosaur museum.

There are paleontological institutions that store the bones of ancient lizards. And in Australia, a special museum of dinosaurs has been opened. In it you can see not only a collection of fossils, but also admire the sculptures of lizards in the garden.

It is known that dinosaurs became extinct at the end of the Cretaceous period, which was approximately 65 million years ago. Something happened on the planet that made all kinds of animals disappear from the face of the Earth. Scientists are still arguing about what could have led to such mass death these representatives of the fauna.

Reasons for the death of dinosaurs

There are about a dozen versions, ranging from quite logical and scientific, ending with extraterrestrial and unlikely. It is known that this species of animals existed for a long time - 125 million years, dominating other representatives of the fauna.

One of the common causes of extinction, which is assumed by the scientists of the world, is the collision of the planet with a large cosmic body. Although we are shown in the movies that this process was short and the dinosaurs died quickly, this is not the case. It is proved that they died out gradually, over a period of about five million years.

The asteroid impact hypothesis is one of the first to have an explanation and evidence. Scientists believe that 65 million years ago a huge celestial body with a diameter of tens of kilometers hit the planet. This contributed to the development of the strongest shock wave, which affected, without exception, all corners of the globe.

All living things, including flora and fauna, instantly perished within the radius of destruction. Natural resources for millennia became unsuitable for existence. Those who managed to survive after the collision also suffered.

Due to the blast wave, volcanoes became more active, the movement of tectonic plates began, and a dense cloud of dust rose into the air to a height of hundreds of kilometers. The atmosphere became polluted, and the ash from the volcanic eruptions was so impenetrable that it blocked the sun's rays for a long time.

The proof of the hypothesis was a crater discovered in the region of the Yucatan Peninsula - Mexico. They named him Chicxulub. According to the results of studies, the period of its formation coincides with the Cretaceous. The asteroid was named Shiva. After its fall, a whole cycle of cataclysms hit the Earth. First, three-hundred-meter waves of boiling water splashed onto land, killing all living things. Hot steam rose into the atmosphere, the ocean literally boiled. Volcanoes began to erupt all over the planet, which disturbed the composition of the air.

Another reason for the death of flora and fauna was acid rain, which long years poisoned the soil. A million years continued increased seismic activity on the planet.

Another proof of the theory was an anomalous find in Italy. In the clay, taken for research, the age of which was equal to 65 million years, they found an excess of the norms by dozens of times of the rare metal iridium on the planet.

Earlier studies of celestial bodies that fell to Earth showed a large concentration of this chemical. Therefore, in the places of their fall, such an iridium anomaly is usually found. To date, two dozen have been found. The level of exceeding the norms in some areas is 120 times higher. All of them date back to the Mesozoic era - the period of extinction of dinosaurs.

Another theory related to the fall of a meteorite to Earth suggests that cataclysms primarily led to the extinction of terrestrial fauna, algae and everything that photosynthesis uses in vegetation. Due to the fact that the sky was impenetrable to sunlight for a long time due to the large accumulation of dust, steam and ash in the layers of the atmosphere, the plants began to die. Accordingly, herbivores suffered from hunger. With a decrease in their number, predators began to die from lack of food. Thus, a process was launched that led to the disappearance of all living things, including dinosaurs.

Interesting!

Skeptics do not agree with this answer to the question about the end of the era of ancient animals, since it has been proven that this period was fatal only for dinosaurs. At the same time, turtles, mammals, birds, snakes and some reptiles remained on the planet.

Supernova

Another reason for the extinction of the dinosaurs. It is popular and often presented to children as lectures in schools, as the main one. Based on it, in sufficient proximity to the planet, a supernova explosion occurred, which sent deadly gamma rays to Earth.

This could completely "turn off" the Earth's magnetic shield, due to which deadly radiation fell on it, which killed most animals and plants.

This hypothesis is also refuted. Cosmic rays are prevented not only by the magnetic shell of the planet, but also by the atmosphere. If the first could disappear for some reason, then the second could not.

Another theory related to the changes that took place on the planet at that time speaks of a violation of the qualitative composition of the air. At that time, oxygen was 40% of the total mass. Some believe that its concentration began to gradually fall, because now its level is much lower. Its amount dropped to a level that had a detrimental effect on dinosaurs. What caused this is unknown.

According to the results of the study, it was proved that in the Mesozoic, the concentration of oxygen was higher than now. Any changes in it could lead to the death of dinosaurs. In this case, it also remains an open question why crocodiles, mammals and other animals survived.

Volcanic winter

There is a version that seismic activity and the shift of tectonic plates led to massive volcanic eruptions. This went on for hundreds of years. There is evidence that on the Hindustan Peninsula in the Mesozoic era, magma actively poured out of faults in the earth. All this in combination led to atmospheric pollution, a decrease in oxygen, and blocked access to sunlight.

When volcanoes erupt, tons of ash, carbon dioxide, sulfur and numerous toxic compounds are released into the environment. Such emissions had a detrimental effect on all living things. Flora and fauna perished in hot magma. At the site of the eruption for many years remained scorched earth, unsuitable for life. The hot soil poisoned the surrounding air with toxic fumes.

Sex depends on the conditions that accompany the period after laying eggs. If the temperature is above the norm, then mainly females are born, with a decrease - males.

Changes in the atmosphere have led to global cooling. This contributed to the fact that more and more often males began to hatch from eggs. Every day the fights for the favor of the female became tougher, which also reduced the population. Over time, there was no one to breed offspring.

global cooling

The most common version of the death of dinosaurs is the onset of the Ice Age, due to which all prehistoric dinosaurs disappeared from the face of the Earth. For children in schools and even in cartoons, it is more often presented with it.

It is believed that due to some cataclysms on the planet, a sharp drop in temperature began. When it reached critical levels for dinosaurs, they began to gradually die. Over time, the population was several hundred, and the last of them froze.

Unfortunately, this version does not have sufficient evidence. Scientist Christopher Scotese compiled a rough timetable. Temperature changes at the time of the transition from the Cretaceous to the Paleogene period were not observed. On the contrary, this indicator has practically not changed for many millions of years. Changes recorded within 10 degrees are easily tolerated by mammals, amphibians and dinosaurs.

Interesting!

The famous ice age with its global cooling came tens of millions of years later at the end of the Eocene period.

Evolution

Most of the previous versions were put forward by physicists and astrophysicists, so they all explain the death of prehistoric reptiles due to cataclysms and cosmic bodies. Biologists see this as their own, more natural reason.

They refute theories related to the fall of a giant meteorite, a collision with a comet or a supernova explosion. The untruthfulness of these judgments is explained by the fact that the dinosaurs did not die immediately after the incident. This process was long - for millions of years.

It has been proven that large space bodies have fallen on the planet more than once, but other biochains have survived these facts. So, it is known about a meteorite 4 kilometers in diameter, which flew to Earth about 2.5 million years ago. At the same time, animals, including marine ones, died. It only happened on the territory within the radius of reach of the tsunami caused by the collision celestial body with the earth's crust. It is possible that during this period there was a so-called "asteroid winter", when the sun's rays did not penetrate the planet, from which the fauna and flora suffered.

At the same time, the species of animals that existed at that time did not become extinct. So, mammoths survived several global cataclysms. The fact is that the biological chain is not one subspecies, but interconnected creatures. They are extremely resilient and able to adapt to any changes. environment, climatic conditions i.e. evolve.

With the development of a new chain, predators among mammals also appeared. They were small in size, so they did not pose any danger to large dinosaurs. But the cubs of the lizards hatched from eggs small enough, they were calmly attacked by predatory progenitors modern families fox or cat.

It was not easy for giant parents to protect the younger generation from small and agile predators. The population gradually decreased.

Dinosaurs are believed to have reached their peak at the end of the Cretaceous. According to the laws of evolution, after that they must "give way" to more perfect beings. And so it happened. Gradually, prehistoric lizards died out, they were replaced by mammals of various species.

Epidemics

Despite their huge size, the immune system of dinosaurs was underdeveloped. This has led to the fact that they have become easy prey for various infections. Scientists believe that already at that time the most dangerous viral and bacteriological diseases were born.

This led to a violation of the pangolins' ability to bear children and adapt to changing environmental conditions.

Mammals at the top of the food chain

At the end of the Cretaceous period, when new varieties of mammals began to appear, and they competed with dinosaurs in the extraction of food, the latter had a hard time. Due to changes in flora, the appearance of flowering plants and the spread of grasses, it became more difficult for large animals to find enough food.

Also, the method of reproduction played an important role. To grow up, the dinosaur first needed to protect the eggs from possible attacks by small predators, then look for a large number of food. Before the lizards reached the size of an adult, a lot of time passed. Not everyone won the fight for food.

In mammals, this is much easier. The cubs are carried by the mother, then they are fed with her milk, which means there was no need to look for food.

Also, the dimensions did not play into the hands of dinosaurs. Mammals were small size, respectively, they needed ten times less food. This means that in conditions of a shortage of resources for food, they were at a higher stage of evolution and easily survived the fall of their brethren.

Unfortunately, all these hypotheses do not have reliable evidence. Scientists are still looking for possible reasons extinction of the dinosaurs.

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