The development of life in the Mesozoic era. Triassic period, Mesozoic era Triassic period Triassic period Mesozoic era
The Mesozoic consists of three periods: Triassic, Jurassic, Cretaceous.
In the Triassic Most of the land was above sea level, the climate was dry and warm. Due to the very dry climate in the Triassic, almost all amphibians disappeared. Therefore, the flourishing of reptiles began, which were adapted to drought (Fig. 44). Among plants in the Triassic, strong development was achieved gymnosperms.
Rice. 44. Various types of reptiles of the Mesozoic era
Of the Triassic reptiles, turtles and hatteria have survived to this day.
Preserved on the islands of New Zealand, the hatteria is a true “living fossil.” Over the past 200 million years, hatteria has remained almost unchanged and, like its Triassic ancestors, has retained the third eye located in the roof of the skull.
Among reptiles, the rudiment of the third eye is preserved in lizards agamas and batbats.
Along with the undoubted progressive features in the organization of reptiles, there was one very significant imperfect feature - inconsistent body temperature. In the Triassic period, the first representatives of warm-blooded animals appeared - small primitive mammals - tricodonts. They originated from ancient beast-toothed lizards. But rat-sized tricodonts could not compete with reptiles, so they did not spread widely.
Yura named after a French city located on the border with Switzerland. During this period, the planet was “conquered” by dinosaurs. They mastered not only land, water, but also air. There are currently 250 known species of dinosaurs. One of the most characteristic representatives of dinosaurs was the giant brachiosaurus. It reached a length of 30 m, weighed 50 tons, had a small head, a long tail and neck.
In the Jurassic period, various types of insects and the first bird appeared - Archeopteryx. Archeopteryx is the size of a crow. Its wings were poorly developed, it had teeth, and a long tail covered with feathers. In the Jurassic period of the Mesozoic there were many reptiles. Some of their representatives began to adapt to life in water.
The rather mild climate favored the development of angiosperms.
Chalk- the name was given because of thick chalk deposits formed from the remains of shells of small marine animals. During this period, angiosperms appear and spread extremely quickly, and gymnosperms are replaced.
The development of angiosperms during this period was associated with the simultaneous development of pollinating insects and insect-eating birds. Angiosperms have developed a new reproductive organ - a flower, which attracts insects with its color, smell and nectar reserves.
At the end of the Cretaceous period, the climate became colder, and the vegetation of the coastal lowlands died. Herbivores and predatory dinosaurs died along with the vegetation. Large reptiles (crocodile) are preserved only in the tropical zone.
In conditions of a sharply continental climate and general cooling, warm-blooded animals - birds and mammals - received exceptional advantages. The acquisition of viviparity and warm-bloodedness were the aromorphoses that ensured the progress of mammals.
During the Mesozoic period, the evolution of reptiles developed in six directions:
1st direction - turtles (appeared in the Permian period, have a complex shell fused with the ribs and breast bones);
5th direction - plesiosaurs (sea lizards with a very long neck, making up more than half of the body and reaching a length of 13-14 m);
6th direction - ichthyosaurs (lizard fish). The appearance is similar to a fish and a whale, short neck, fins, swim with the help of the tail, legs control the movement. Intrauterine development - live birth of offspring.
At the end of the Cretaceous period, during the formation of the Alps, climate change led to the death of many reptiles. During excavations, the remains of a bird the size of a pigeon, with the teeth of a lizard, which had lost the ability to fly, were discovered.
Aromorphoses that contributed to the appearance of mammals.
1. The increasing complexity of the nervous system and the development of the cerebral cortex influenced changes in animal behavior and adaptation to the living environment.
2. The spine was divided into vertebrae, the limbs were located from the abdominal part towards the back.
3. For intrauterine bearing of cubs, the female has developed a special organ. The cubs were fed milk.
4. To preserve body heat, hair appeared.
5. There was a division into the systemic and pulmonary circulation, and warm-bloodedness appeared.
6.Lungs have developed with numerous bubbles that enhance gas exchange.
1. Periods of the Mesozoic era. Triassic. Yura. Bor. Tricodonts. Dinosaurs. Archosaurs. Plesiosaurs. Ichthyosaurs. Archeopteryx.
2. Aromorphoses of the Mesozoic.
1.What plants were widespread in the Mesozoic? Explain the main reasons.
2. Tell us about the animals that developed in the Triassic.
1.Why is the Jurassic period called the period of dinosaurs?
2. Discuss aromorphosis, which is the cause of the appearance of mammals.
1. In what period of the Mesozoic did the first mammals appear? Why weren't they widespread?
2.Name the species of plants and animals that developed during the Cretaceous period.
In what period of the Mesozoic did these plants and animals develop? Opposite the corresponding plants and animals, put the capital letter of the period (T - Triassic, Y - Jurassic, M - Cretaceous).
1.Angiosperms.
2. Tricodonts.
4. Eucalyptus trees.
5. Archeopteryx.
6. Turtles.
7. Butterflies.
8. Brachiosaurs.
9. Hatterias.
11. Dinosaurs.
At the end of the Paleozoic, mountain building occurred, causing the rise of land and the emergence of the Urals and Altai. All this leads to a further increase in climate aridity, which began in the Permian. The land area was much larger than it is now. The Mesozoic is rightly called the era of reptiles. Their heyday, widest divergence and extinction occur precisely in this era.
Triassic. In the Triassic, the areas of inland water bodies were greatly reduced, and desert landscapes developed. In arid climates, many land organisms whose individual stages of life are associated with water die out. Most amphibians die out, tree ferns, horsetails and mosses almost completely disappear. Instead, terrestrial forms begin to predominate, in the life cycle of which there are no stages associated with water. Among plants in the Triassic, gymnosperms reached strong development, and among animals, reptiles.
Of the Triassic reptiles, turtles, crocodiles and tuataria have survived to this day. Hatteria, now preserved only on a few islands near New Zealand, is a real “living fossil.” It has changed very little over the past 200 million years and has retained, like its Triassic ancestors, a third eye located in the roof of the skull. Herbivorous and carnivorous dinosaurs appeared in the Triassic. Their sizes were relatively small;
In the seas, bony fish are developing, while the diversity of cartilaginous and lobe-finned fish is gradually declining. Cephalopods are becoming more and more diverse. The abundance of fish and shellfish allowed some reptiles to develop an aquatic environment rich in food. Among aquatic forms, the most famous are ichthyosaurs, which in body structure were very similar to sharks and modern dolphins.
Along with the undoubted progressive features in the organization of reptiles, there is one very significant imperfect feature - inconsistent body temperature. When the environmental temperature drops, reptiles become lethargic and numb. Throughout the relatively warm Mesozoic, the unstable body temperature of reptiles was not too much of a negative property. Already in the Triassic, the first representatives of warm-blooded animals appeared - small primitive mammals. Mammals of the Triassic were apparently oviparous, like the modern echidna and platypus.
Yura. In the Jurassic, there is some expansion of the areas of warm-water seas. In the seas, cephalopods - ammonites and belemnites - are very numerous. The spiral-shaped shell of ammonites is often found in the sediments of Mesozoic seas. Belemnites were somewhat reminiscent of modern squids. The remnant of their skeleton ("devil's finger") is common in sediments of Mesozoic seas.
Marine reptiles are very diverse. In addition to ichthyosaurs, plesiosaurs appear in the Jurassic seas - animals with a wide body, long flippers and a serpentine neck. Marine reptiles seemed to divide food resources among themselves: plesiosaurs hunted in the shallow waters of the coastal zone, and ichthyosaurs hunted in the open sea.
In the Jurassic, reptiles began to master the air environment.
The diversity of flying insects created conditions for the development of insectivorous flying dinosaurs. Large lizards began to feed on small flying lizards.
On land in the Jurassic, giant herbivorous dinosaurs are found. The body length of some of them reached 30 m. The dinosaurs that hunted them also reached large sizes.
Among plants during this period, the dominance of gymnosperms remains.
Chalk Some of them, such as sequoias, have survived to this day.
. The Cretaceous period (or chalk) is named due to the formation of chalk in the marine sediments of that time. It arose from the remains of the shells of protozoan animals - foraminifera.
During this period, angiosperms appear and spread extremely quickly, and gymnosperms are replaced.
Reptiles were introduced in the Cretaceous by new dinosaurs. Some of them walked on their hind legs and resembled ostriches; Giant forms were still encountered. Protection from predatory reptiles went in the direction of gigantism in some herbivorous dinosaurs, while in others it went towards the development of protective weapons - horns and bony shields. Some of the herbivorous dinosaurs vaguely resembled rhinoceroses. The flying lizards were very diverse.
The birds still retained their teeth, but otherwise did not differ significantly from modern birds. In the second half of the Cretaceous, marsupials and placental mammals arose. Long-term gestation of cubs in the mother's body, feeding of embryos through the placenta, which connects the bloodstreams of the mother and fetus, are the most important adaptations of mammals to unstable conditions of existence.
Unconstant body temperature and egg laying made reptiles more dependent on fluctuations in environmental temperature and limited the possibility of their penetration into the polar regions. Having acquired viviparity, caring for offspring and warm-bloodedness, mammals became less dependent on environmental changes than reptiles. These circumstances led in the Cenozoic to the replacement of the dominance of reptiles by the dominance of mammals. The acquisition of viviparity and warm-bloodedness were the aromorphoses that ensured the progress of mammals.
Angiosperms developed a flower - a reproductive organ that attracts insects by color, smell and nectar reserves. Insects, feeding on nectar, became carriers of pollen. The transfer of pollen by insects, compared to wind pollination, leads to less waste of gametes. The same process of economical expenditure of gametes is observed in a number of vertebrates. The death of gametes during external fertilization (in fish, amphibians) is much greater than during internal fertilization (in reptiles, birds, mammals).
At the end of the Cretaceous, the climate changed towards sharp continentality and general cooling. Ammonites and belemnites die out in the seas, and after them the sea lizards that fed on them - plesiosaurs and ichthyosaurs. On land, moisture-loving vegetation that served as food for herbivorous dinosaurs began to decline, which led to their disappearance; Carnivorous dinosaurs also became extinct. Of the reptiles, large forms have been preserved only in the equatorial regions - crocodiles, turtles and tuataria. Most of the surviving reptiles (lizards, snakes) were small in size.
The Triassic period on Earth lasted about 45 million years. From its beginning to the present day, approximately 220 million years have passed. In the Triassic, land prevailed over sea. There were two continents. The North Atlantic and Asian continents merged to form the Northern Land. In the southern hemisphere lay the former Gondwana. Asia connected with Australia and New Zealand. All of Southern Europe, the Caucasus and Crimea, Iran, the Himalayas and North Africa were flooded by the Tetke Ocean. Large mountain ranges did not re-emerge at this time, but the mountains formed in previous periods were still high. Volcanic eruptions occurred frequently. The climate of the Triassic period was harsh and dry, but quite warm. Deserts in the Triassic are numerous.
From plants Gymnosperms were noticeably dominant: sago, conifer and ginkgo. Of the seed ferns, Glossopteris continued to exist. At the end of the period, peculiar ferns appeared, especially numerous in the subsequent Jurassic period, the leaves of which resembled the leaves of seed plants in veining. Triassic horsetails are much closer to modern horsetails than Paleozoic ones.
Great changes have taken place in the lives of the inhabitants of the continents. The predominance of land over the sea, which began back in the Permian period, and the progressive drainage of many fresh water bodies in the Triassic period led to the fact that many freshwater fish now moved to the seas, and only lungfish, close to the present ones, still lived in the surviving freshwater basins. At the end of the Triassic period, stegocephalians became extinct. These were the last representatives of labyrinthine-toothed stegocephals, so named because the enamel on their teeth had a complex folded structure. All stegocephalians, fleeing the dry climate and competition with reptiles, became aquatic, and some even went to live in the sea. Most of them were very large animals. For example, in Mastodonsaurus the skull length reached 1 m.
At the beginning of the Triassic period there lived direct ancestors of modern frogs. These protobatrachus are small, 10 cm long, animals whose general appearance is more reminiscent of toads than real frogs. Their skin is tuberous, and their hind legs are better suited for swimming than for jumping.
Reptiles have changed especially dramatically; whole skulls finally died out. In the second half of the period, the first turtles appeared, which, unlike modern ones, still had teeth in their palates, while their jaws were covered with a horny beak.
During the Triassic period they developed intensively, but at the end of it the last animal-like reptiles became extinct. Of these, herbivores and already completely toothless Shtalekeria reached the size of a large rhinoceros. Smaller in size was the predatory belezodont, about 1.5 m long.
Particularly interesting are the small animal-like reptiles ictidosaurs, close to mammals. Thus, caromis, an animal the size of a rat, is already a real mammal in the structure of its skull, and only the additional bones present in its lower jaw indicate that this animal is still a reptile.
Of the other reptiles in the Triassic period, proboscis-heads developed, the closest relatives of the modern New Zealand tuateria, which, although similar to ordinary lizards, differ from them in their structure. Hatteria still retains many ancient features in its structure. In its skull there are two temporal (zygomatic) arches, and not one, like in lizards. Its upper jaw hangs down in the form of a small beak. The teeth on the jaws do not sit in separate cells, but in a common groove. In addition to the usual ribs, “ventral ribs” also develop on the belly. The biconcave vertebrae resemble those of fish. Among the proboscis-heads in the Triassic lived stenaulorhynchus - large burrowing animals that may have fed on roots. In the seas, along the shores of the continents, long-snouted proboscis-heads were encountered - destroyers of marine mollusks. In the area with them, placodonts, somewhat reminiscent of sea turtles, hunted for mollusks, in which, instead of small teeth, real millstones were formed on the palate for crushing shells.
Nothosaurs related to placodonts also led an aquatic lifestyle. These long-necked animals could still use their paws (flippers) to walk on the ground. Nothosaurs gave rise to plesiosaurs, common marine reptiles of the following periods. The first fish lizards, or ichthyosaurs, appeared in the northern waters. They were not yet as well adapted to swimming in the sea as their descendants, whose tail became like a fish.
The most remarkable thing is that ichthyosaurs did not lay eggs, like ordinary reptiles, but gave birth to live young, like mammals. With the Triassic, the flourishing of the group of cellular-toothed reptiles began. The most ancient forms of them were relatively small carnivores. Instead of the usual movement on four legs, these animals adapted to walking on two, and therefore their hind legs became much longer than their front ones.
This was Saltoposuchus, an animal more than 1 m in size. By the end of the Triassic, some cellular-toothed reptiles switched to an aquatic lifestyle. They again began to walk on four legs and in appearance were somewhat reminiscent of the crocodiles that were still absent at that time. The length of such a crocodile-shaped prestosuchus was at least 5 m. The first, not yet very large, rare dinosaurs appeared mainly on the Northern land. Some of them were not small, up to 1 m in length, and led a predatory lifestyle. They walked on their hind legs, which were longer than their front legs. In some ways, dinosaurs resembled birds: the bones of their skeletons were hollow, filled with air, and the first toe on the hind legs was facing backwards.
Other dinosaurs, such as Plateosaurus, were much larger, reaching 6 m in length. The difference in the structure of their front and hind legs is small, and their teeth are blunt. These were the ancestors of the herbivorous giants of the Jurassic period.
It is not surprising that, given the abundance of animal-like reptiles in the Triassic, we also find real mammals here. The oldest mammal known to us, the size of a marmot, is called “tritylodont”. It belongs to the group of many tuberculate-toothed mammals, so called because they had numerous tubercles arranged in two or three rows on their molars. They didn't have fangs. One pair of incisors in the upper jaw and the only pair in the lower jaw were enlarged. Many tubercle-toothed animals ate plant foods. They probably still laid eggs rather than giving birth to live young, just like modern Australian monotremes: the platypus and the echidna. Modern oviparous mammals are toothless, but platypus embryos have multitubercular tooth primordia. Therefore, many tuberculates are considered the closest relatives of the Australian monotremes, which still retain many features characteristic of reptiles.
At the bottom of the Triassic sea lived numerous six-rayed corals, close to modern ones. Bivalves and gastropods were abundant, replacing brachiopods. New sea urchins and lilies were often encountered. But numerous ammonites reached particular diversity in this period. At the same time, the first belemnites appeared - animals close to modern sea cuttlefish, also classified as cephalopods. Hidden under their skin was a calcareous skeleton in the form of a plate ending in a sharp spike. This spine is usually preserved in fossil form and is called the "devil's finger."
In addition to shark fish, quite a lot of bony fish already lived in the sea, whose ancestors moved here from fresh water. Lobe-finned fish and relatives of modern sturgeon fish, as well as armored pike and mud fish of North America, were found here. In the structure of their scales, tail and internal organs, these fish still differed from real bony fish.
TRIASSIC
The Triassic period got its name from the fact that its deposits include three different rock complexes: the lower - continental sandstone, the middle - limestone and the upper - Naper.
The most characteristic deposits of the Triassic period are: continental sandy-clayey rocks (often with lenses of coal);marine limestones, clays, shales; lagoonal anhydrites, salts, gypsum.
During the Triassic period, the northern continent of Laurasia united with the southern one - Gondwana. A large bay that began in the east of Gondwana extended all the way to the northern coast of modern Africa, then turned south, almost completely separating Africa from Gondwana. A long bay stretched from the west, separating the western part of Gondwana from Laurasia. Many depressions appeared on Gondwana, which were gradually filled with continental sediments.
During the Middle Triassic, volcanic activity intensified. Inland seas become shallow, andnumerous depressions. The formation of the mountain ranges of Southern China and Indonesia begins. In the territory of the modern Mediterranean, the climate was warm and humid. It was cooler and wetter in the Pacific zone. Deserts dominated the territory of Gondwana and Laurasia. The climate of the northern half of Laurasia was cold and dry.
Along with changes in the distribution of sea and land, the formation of new mountain ranges and volcanic areas, there was an intensive replacement of some animal and plant forms by others. Only a few families moved from the Paleozoic era to the Mesozoic. This gave grounds to some researchers to claim about the great catastrophes that occurred at the boundary of the Paleozoic and Mesozoic. However, when studying the deposits of the Triassic period, one can easily verify that there is no sharp line between them and the Permian deposits; therefore, some forms of plants and animals were replaced by others, probably gradually. The main reason was not catastrophes, but the evolutionary process: more perfect forms gradually replaced less perfect ones.
The seasonal temperature changes of the Triassic period began to have a noticeable effect on plants and animals. Certain groups of reptiles have adapted to cold seasons. It is from these groups, Mammals arose in the Triassic, and birds arose somewhat later. At the end of the Mesozoic era, the climate became even colder. Deciduous woody plants appear, which partially or completely shed their leaves during cold seasons. This feature of plants is an adaptation to a colder climate.
The cooling during the Triassic period was insignificant. It manifested itself most strongly in northern latitudes. The rest of the area was warm. Therefore, reptiles felt quite well in the Triassic period. Their most diverse forms, with which small mammals were not yet able to compete, settled across the entire surface of the Earth. The rich vegetation of the Triassic period also contributed to the extraordinary flourishing of reptiles.
Gigantic forms of cephalopods developed in the seas. The diameter of the shells of some of them was up to 5 m. True, even now the seas are inhabited by gigantic cephalopods, for example squids, reaching 18 m in length, but in the Mesozoic era there were much more gigantic forms.
The composition of the atmosphere of the Triassic period changed little compared to the Permian. The climate became wetter, but deserts remained in the center of the continent. Some plants and animals of the Triassic period have survived to this day in the region of Central Africa and South Asia. This suggests that the composition of the atmosphere and the climate of individual land areas have remained almost unchanged throughoutMesozoic and Cenozoic eras.
And yet stegocephalians became extinct. They were replaced by reptiles. More perfect, mobile, well adapted to a variety of living conditions, they ate the same food as stegocephals, settled in the same places, ate the young of stegocephals and ultimately exterminated them.
Among the Triassic flora, calamites, seed ferns and cordaites were also occasionally found. True ferns, ginkgo ferns, bennetite ferns, cycads, and conifers predominated. Cycads still exist in the Malay Archipelago region. They are known as sago palms. In appearance, cycads occupy an intermediatea place between palms and ferns. The cycad trunk is quite thick and columnar. The crown consists of hard, feathery leaves arranged in a corolla. Plants reproduce using macro and microspores
Triassic ferns were coastal herbaceous plants with wide, dissected leaves.with reticulate venation. Volttsia has been well studied among coniferous plants. It had a thick crown and cones like those of a spruce.
Triassic
The Triassic was a time of widespread land development. Only in certain places did the sea advance on land: in the Caspian lowland, on the plains of Germany, in the north - in the area of the Spitsbergen islands. The sea also expanded in the center of the southern continent of Gondwana - where the Mozambique Strait is now located. This began to form the Indian Ocean depression in the Gondwana continent.
Hot clouds of volcanic ash swirled over the Siberian platform: numerous volcanoes sparkled from the middle reaches of the Angara to the northern outskirts of the platform, from the Lena in the east to the Yenisei in the west. Throughout this vast area, volcanic rocks have intruded into ancient Paleozoic strata.
Ancient cracks stretch for tens and hundreds of kilometers, filled with frozen magma that rose from the depths of the earth over 150 million years ago.
In many places we find layers of Triassic sedimentary rocks. These are mainly variegated marls, sandstones and limestones. They are found in Siberia - in the Verkhoyansk-Okhotsk Mountains and in the Ussuri River basin; come out in the lower Volga region, near Lake Baskunchak, in the Transcaspian region, in the Crimea, in the Caucasus.
On the Crimean coast, the thickness of Triassic sandstones and clayey shales reaches several thousand meters.
The layers of this period contain numerous remains of animals and plants. They tell us about life that once boiled in the seas and on land of the Triassic continents.
Various types of shellfish filled the shallow seas. Algae covered the bottom with a dense green carpet. Sea urchins crawled in their thickets.
The first belemnites appeared - mollusks with an internal shell. Their elongated bodies swam quickly in the clear water, truly resembling an arrow (“belemnon” in Greek means “arrow”). Belemnites moved with the help of a stream of water, which they threw out with force, thus receiving a push in the opposite direction. The inner shell of belemnites was covered with skin on top. Parts of this shell have survived to this day. On the banks of rivers, in ravines and in other places where Mesozoic layers come to the surface, smooth stone sticks pointed at one end are often found. People call them thunder arrows or “devil's fingers.” These sticks are the fossilized remains of belemnites, cone-shaped outgrowths of the inside of their shells.
Belemnite.
During the Triassic, changes occurred again in the Earth's climatic conditions.
Young mountain ranges that formed along the ocean coasts and fenced off the land from humid sea winds created conditions for a harsh continental climate. Tree ferns and horsetails began to gradually disappear, and the land became covered with cycads and conifers, better adapted to the changed climatic conditions.
Reptiles found abundant food in the forests. They have achieved significant diversity and increased in size.
...What a massive bone lies under the glass display case in the museum hall where fossil remains of the Triassic are collected! What animal did it belong to?
Our “time machine” instantly takes us to the edge of a Triassic forest through which a large river flows.
Tree-like horsetails grow in small groups near the water. They are already living out their lives; they have been replaced by forests of primitive coniferous gymnosperms. Spreading leaves of cycads hung over the water.
A huge amphibian lies on the sand, lazily spreading its paws, lowering the lower part of its wide, flat head into the water.
Near the horsetails, lurking in wait for prey, was a reptile with a long tail and disproportionately small front paws. In appearance, it resembles a large lizard standing on its hind legs. This is a cellular-toothed lizard - the ancestor of birds and “terrible lizards” - dinosaurs that will appear on Earth millions of years later. Scientists called it “cell-toothed” because each tooth sat in a special cell.
In the middle of the clearing, a plateosaurus walking on its hind legs froze in a wary pose. Its massive body, resting on its tail, reaches 5 meters in length. Turning his small head on his long neck towards the river, he looks at the crocodile-shaped belodont crawling out of the water onto the shore...
Plateosaurus on the edge of a Triassic forest.
The Triassic period lasted about 30 million years - the time of cephalopods, primitive coniferous plants and lizards. Cold-blooded reptiles - lizards - inhabited the coasts of the seas, forest thickets, and began to penetrate desert spaces in the interior of the continents.
Another millions of years will pass - and lizards will become the rulers of the Earth. They will take possession of all the land, the waters of the seas, and rise into the air. But for now they are forced to be content with the rather modest role that they had to play among many other animals that lived on Earth in the Triassic period of its history.
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