The history of the Earth has four and a half billion years. This huge period of time is divided into four eons, which in turn are divided into eras and periods. The final fourth eon - Phanerozoic - includes three eras:
- Paleozoic;
- Mesozoic;
- Cenozoic.
The Mesozoic period is significant for the appearance of dinosaurs, the birth of the modern biosphere and significant geographical changes.
Periods of the Mesozoic Era
The end of the Paleozoic era was marked by the extinction of animals. The development of life in the Mesozoic era is characterized by the appearance of new types of creatures. First of all, these are dinosaurs, as well as the first mammals.
The Mesozoic lasted one hundred and eighty-six million years and consisted of three periods, such as:
- Triassic;
- Jurassic;
- chalky.
The Mesozoic period is also characterized as the era of global warming. There have also been significant changes in the tectonics of the Earth. It was at that time that the only existing supercontinent broke up into two parts, which subsequently divided into the continents that exist in the modern world.
Triassic period
Triassic periodThis is the first stage of the Mesozoic era. The Triassic lasted for thirty-five million years. After the catastrophe that occurred at the end of the Paleozoic on Earth, conditions are observed that are little conducive to the prosperity of life. There is a tectonic fault of the Pangea continent, active volcanoes and mountain peaks are formed.
The climate is getting warm and dry, and as a result, deserts are forming on the planet, and the level of s alt in water bodies is rising sharply. However, it was at this unfavorable time that the first dinosaurs, mammals and birds appeared. In many ways, this was facilitated by the absence of clearly defined climatic zones and the maintenance of the same temperature throughout the globe.
Triassic wildlife
The Triassic period of the Mesozoic is characterized by a significant evolution of the animal world. It was during the Triassic period that those organisms arose that subsequently shaped the appearance of the modern biosphere.
Cynodonts appeared - a group of lizards, which was the ancestor of the first mammals. These lizards were covered with hair and had strongly developed jaws, which helped them eat raw meat. Cynodonts laid eggs, but females fed their young with milk. The Triassic also gave birth to the ancestors of dinosaurs, pterosaurs and modern crocodiles - archosaurs.
Due to the arid climate, many organisms have changed their habitat to aquatic. Thus, new species of ammonites, mollusks, as well as bony and ray-finned fish appeared. But the main inhabitants of the deep sea were predatory ichthyosaurs, which, asevolution began to reach gigantic proportions.
By the end of the Triassic, natural selection did not allow all the animals that appeared to survive, many species could not stand the competition with others, stronger and faster. Thus, by the end of the period, thecodonts, the progenitors of dinosaurs, dominated on land.
Plants in the Triassic period
The flora of the first half of the Triassic did not differ significantly from the plants of the end of the Paleozoic era. Various types of algae grew in abundance in the water, seed ferns and ancient conifers spread widely on land, and lycosid plants in coastal areas.
By the end of the Triassic, a cover of herbaceous plants covered the land, which greatly contributed to the appearance of a variety of insects. Also appeared plants of the mesophytic group. Some cycad plants have survived to this day. This is a sago palm growing in the Malay Archipelago zone. Most of the plant varieties grew in the coastal areas of the planet, and conifers dominated on land.
Jurassic
This period is the most famous in the history of the Mesozoic era. Jura - European mountains that gave the name to this time. Sedimentary deposits of that era have been found in these mountains. The Jurassic period lasted fifty-five million years. Acquired geographical significance due to the formation of modern continents (America, Africa, Australia, Antarctica).
The separation of the two continents of Laurasia and Gondwana that existed until that moment served to form new bays and seas andrise in the level of the world's oceans. This favorably affected the climate of the Earth, making it more humid. The air temperature on the planet dropped and began to correspond to a temperate and subtropical climate. Such climatic changes have largely contributed to the development and improvement of the animal and plant world.
Animals and plants of the Jurassic period
The Jurassic period is the era of the dinosaurs. Although other forms of life also evolved and acquired new forms and types. The seas of that period were filled with many invertebrates, the body structure of which is more developed than in the Triassic. Bivalve molluscs and intrashell belemnites, which were up to three meters long, were widespread.
The world of insects has also received evolutionary growth. The appearance of flowering plants provoked the appearance of pollinating insects. New species of cicadas, beetles, dragonflies and other terrestrial insects have emerged.
Climatic changes that occurred during the Jurassic period led to heavy rainfall. This, in turn, gave impetus to the spread of lush vegetation on the surface of the planet. Herbaceous fern and ginkgo plants predominated in the northern zone of the earth. The southern belt was made up of tree ferns and cycads. In addition, various coniferous, cordaite and cycad plants filled the Earth.
Dinosaur Era
In the Jurassic period of the Mesozoic, reptiles reached their evolutionary peak, ushering in the era of the dinosaurs. The seas were dominated by giant dolphin-like ichthyosaurs and plesiosaurs. If aichthyosaurs were inhabitants of an exclusively aquatic environment, then plesiosaurs from time to time needed access to land.
Dinosaurs living on land were striking in their diversity. Their sizes ranged from 10 centimeters to thirty meters, and they weighed up to fifty tons. Among them, herbivores predominated, but there were also ferocious predators. A huge number of predatory animals provoked the formation of some defense elements in herbivores: sharp plates, spikes and others.
The air space of the Jurassic period was filled with dinosaurs that could fly. Although for the flight they needed to climb a hill. Pterodactyls and other pterosaurs flocked and hovered above the ground in search of food.
Cretaceous
When choosing a name for the next period, writing chalk, formed in the deposits of dying invertebrate organisms, played the main role. The period called the Cretaceous became the final one in the Mesozoic era. This time lasted eighty million years.
The formed new continents are moving, and the Earth's tectonics is becoming more and more familiar to modern man. The climate became noticeably colder, at this time the ice caps of the north and south poles formed. There is also a division of the planet into climatic zones. But in general, the climate remained warm enough, helped by the greenhouse effect.
Cretaceous biosphere
Belemnites and mollusks continue to evolve and spread in water bodies,sea urchins and the first crustaceans also develop.
In addition, fish with a hard-bone skeleton actively develop in reservoirs. Insects and worms progressed strongly. On land, the number of vertebrates increased, among which reptiles occupied the leading positions. They actively absorbed the vegetation of the earth's surface and destroyed each other. In the Cretaceous period, the first snakes arose, which lived both in water and on land. Birds that began to appear at the end of the Jurassic period became widespread and actively developed during the Cretaceous period.
Among the vegetation, flowering plants are the most developed. Spore plants died out due to the characteristics of reproduction, giving way to more progressive ones. At the end of this period, gymnosperms noticeably evolved and began to be replaced by angiosperms.
The end of the Mesozoic era
The history of the Earth has two global catastrophes that led to the mass extinction of the animal world of the planet. The first, Permian catastrophe was the beginning of the Mesozoic era, and the second marked its end. Most of the animal species that actively evolved in the Mesozoic died out. In the aquatic environment, ammonites, belemnites, bivalve mollusks ceased to exist. Dinosaurs and many other reptiles disappeared. Many species of birds and insects also disappeared.
Until now, there is no proven hypothesis about what exactly was the impetus for the mass extinction of the fauna in the Cretaceous period. There are versionsabout the negative impact of the greenhouse effect or about the radiation caused by a powerful cosmic explosion. But most scientists are inclined to believe that the cause of extinction was the fall of a gigantic asteroid, which, when it hit the Earth's surface, raised a mass of substances into the atmosphere that closed the planet from sunlight.
