Dinosaurs - are ancient creatures that have appeared on the planet about 225 million years ago.For 160 million years, these animals dominated the planet.The period of the disappearance took about 5 million years, and now about 65 million years in the animal world they are missing.There are many hypotheses why dinosaurs disappeared.How to become extinct and cease to exist, these animals, we describe in this article.
appearance of dinosaurs
Earth was populated by different species of plants and animals 3 billion years ago.In the evolution of plants and animals come and go, and each process has its time period and the period.Dinosaurs lived on the planet in the Mesozoic era - is the Triassic, Jurassic and Cretaceous periods.
first simple plants were algae, and the first animals - small clams.The appearance of fish occurred about 500 million years ago.Approximately 370 million years ago came the first land animals - amphibians.Reptiles - a new group of animals, which appeared about 300 million years ago.The animals were scaly skin, they can lay eggs and reside on land.The next in the chain of evolution have become dinosaurs.Extinct animals gave impetus to the development of science such as paleontology.
One of the amazing animals that lived on the planet, are the dinosaurs.How to become extinct and how to live these great animals can be judged only by the fossilized remains.According to the fossil record, we can conclude that they were reptiles like crocodiles, lizards, turtles and snakes.Size dinosaurs changed over a wide range - from tiny to giant.They possess four limbs and tail.They are standing and moving dinosaurs on the straight course, some - on its hind legs, the other - on all four, and others could move on two and on four limbs.Many dinosaurs had long necks and teeth.Habitat them it was significant, but 65 thousand years ago, they suddenly became extinct.
Dinosaurs are divided into two groups: Saurischia and Ornithischia.The difference between the groups is the structure of the pelvis.In the structure of the pelvis dinosaurs Saurischia chetyrёhluchevoe, while ornithischian - trёhluchevoe.In some species ornithischian had horns, spikes, armor.
The emergence of interest in dinosaurs
In the 30 years of the XIX century, were first discovered the fossilized remains of dinosaurs.Then the archaeologists did not attach much importance to them, and only after some time it became clear that these fossils belong to the ancient animals.The concept of "dinosaur" was introduced by the British zoologist Richard Owen in the middle of the XIX century.From Latin, "dinosaur" means "terrible", "dangerous", "awful" and from Greek - "lizard" "lizard".Since then, interest in these animals is constantly growing.How many years ago the dinosaurs became extinct?The answer to this question is provided by the science of paleontology.Ancient animal study researchers, starred in the movie, they become heroes of books.And in spite of this interest, the question of why the dinosaurs became extinct, there is no exact answer.
At the end of the Permian period was the formation of a single continent - Pangaea.A characteristic feature of this time there was a global volcanic activity and the disappearance of about 90% of the animals.Best of all are adapted to the new conditions reptiles.At the beginning of the Triassic appeared a group of reptiles called "pelycosaur."By the mid-Triassic period, they were replaced by a group of reptiles called "therapsids."In parallel with the therapsid developed a new group of reptiles - archosaurs.This group of reptiles is the ancestor of all dinosaurs, pliosaurs, crocodylomorpha, ichthyosaurs, and pterosaurs plakodontov.The following species of reptiles was called thecodonts and has been adapted to life on land.And they received from their development of the dinosaurs.Extinct animals are well adapted and occupied the dominant position in the land, in water and in the air.
During the Triassic dinosaurs existed following: tselofizis, mussaurus and procompsognathus.We develop and evolve vegetable dinosaurs.
largest animals lived in the Jurassic period.In the Late Jurassic period, began to appear land animals - Brachiosaurus, Diplodocus, and others.
in the Cretaceous seas and oceans began to prevail ravenous reptiles.There are new kinds of dinosaurs.
The end of
Cretaceous period - a period of prosperity giant lizards, pterodakteley air and sea reptiles.At the end of the Cretaceous period, there is a split in the continent Pangea, Gondwana and Laurasia.The Earth's climate became much colder at the poles are formed ice caps.There are flowering plants, and increases the number of insects.
All this has led to the extinction of many plant and animal species, including the dinosaurs.They do not become extinct overnight, but when you consider that their domination lasted for 160 million years, their disappearance happened pretty quickly.Causes of the disaster, which occurred in the Cretaceous period, is still not clear.
But the dinosaurs become extinct?The descendants of the ancient reptiles are available now crocodiles, lizards and birds.The first birds appeared in the Cretaceous era, and by the end of the era have already developed plumage.When the dinosaurs, the birds took over the baton of evolution.
Astrophysical hypothesis extinction
asteroid is one of the most common versions.The time of his fall coincides with the formation of the crater Chicxulub (Mexico, Yucatan Peninsula).These events occurred approximately 65 million years ago, at a time when the dinosaurs became extinct.Perhaps the fall of an asteroid caused the destructive actions, so that there was a mass extinction of all life.
hypothesis tumble states that the asteroid happened several times.In addition, there Chicxulub crater Shiva crater in the Indian Ocean, which was formed around the same time.This hypothesis explains why the extinction occurred gradually.More
a version of a supernova explosion and the collision of a comet with the Earth.
geological and climatic hypothesis extinction
The planet has undergone substantial changes during the period when the dinosaurs started to disappear.As extinct animals, the theory involves changes in average annual and seasonal temperatures.Large individuals need a warm and equable climate.Volcanic activity could result in a change in the composition of the atmosphere and cause the greenhouse effect.Large volcanic ash could trigger a volcanic winter, thus changing the illumination of the earth.A significant decrease in the sea level, the cooling of the ocean, changes in the composition of sea water and a sharp jump in the magnetic field of the Earth also may have contributed to the extinction of the dinosaurs.
evolutionary-biological hypothesis extinction
One of the hypotheses that group adheres to the situation of occurrence of a mass epidemic.It is possible that the dinosaurs could not adapt to the changing vegetation, causing poisoning.Chances destruction of eggs and the first cubs predatory mammals.More there is a theory that during the Ice Age disappeared females.Scientists have proposed another version of the death of the dinosaurs - gasp: in the atmosphere has been a sharp decrease in the amount of oxygen.
Why did the dinosaurs disappear?
Why did the dinosaurs disappear?How these ancient extinct animals?Answers to these questions are a variety of theories and hypotheses, but none of them does not respond to all questions fully.It is known that the extinction of species started long before the crash, and an astronomical hypothesis in this case is questionable.Many theories no evidence, for example, from the hypothesis of the regression of the oceans or changes in the magnetic field.Also, the lack of completeness of the fossil record can give a distorted picture.
Combining hypotheses generates a clearer picture.Hypotheses, complementing each other, give answers to more questions, and then the picture is more legible and detailed.
process of evolution - the extinction of the old and new education - consistent.And the evolution of the dinosaurs until the end of the Cretaceous period occurred naturally.But for some reason at the end of the Cretaceous period, the former species died out and new ones did not appear, and, as a consequence, there was a complete extinction of this species.
terms of paleontology
version of the great extinction based on the following facts:
- emergence of flowering plants.
- gradual climate change caused by the drift of continents.
According to the scientific world, observed the following picture.Root development of flowering plants, they are more adaptable to soils quickly replaced other types of vegetation.Began to appear the insects that fed on flowering plants and insects appearing earlier began to fade.
root system began to grow flowering and prevent soil erosion.Terrestrial longer blurred, and vanished into the oceans nutrient material.This led to the destruction and depletion of ocean algae, which in turn, are producers of biomass in the ocean.In the water there was a violation of the ecosystem, which led to mass extinction.It is believed that the flying dinosaurs are closely related to the sea, so the chain of extinction spread to them.On land they were trying to adjust to the green mass.Began to appear small mammals and predators of small size.It is a threat to the offspring of dinosaurs as eggs and cubs dinosaurs become food for predators appeared.This creates the conditions for the emergence of new negative species.
When the dinosaurs, the Mesozoic Era is over, it is over and active tectonic, climatic and evolutionary activity.
Children and dinosaurs
interest in ancient animals is not only in adults but also in children.Today, the project "Why dinosaurs became extinct?" Included in the program of kindergartens and primary schools.The uniqueness of this activity is that the child develops cognitive abilities alone, looking for answers to questions and gain new knowledge.The question of why the dinosaurs became extinct, for children as curious as it is for scientists.Interest is primarily due to the fact that these animals on earth today there is no precise answer to the question about the causes of their disappearance have not yet been received.