4th period of the Paleozoic. Paleozoic era PZ • • Eon

Eon - Phanerozoic Beginning of the era 541 million years ago End of the era 298.9 million years ago Duration 242.1 million years

Periods Paleozoic Cambrian Ordovician Silurian Devonian Carboniferous Permian (D) (C) (P) (S) (O) (€) 541,485, 4,443, 4,419, 2,358, 9,298.9 Duration (million years) 55.6 42 42 24, 2 60, 3 60

TECTONICS Cambrian Began about 542 million years ago, ended 488 million years ago, Cambrian lasted about 54 million years By the beginning of the era and throughout the Cambrian, ancient platforms (South American, African, Arabian, Australian, Antarctic, Indian), turned to 180°, were combined into a single supercontinent called Gondwana.

Ordovician Ordovician, the second system from the bottom of the Paleozoic group, corresponding to the second period of the Paleozoic era of the geological history of the Earth. It is underlain by the Cambrian and overlain by the Silurian systems. It began 485.4 ± 1.9 million years ago and ended 443.4 ± 1.5 million years ago. Thus it continued for about 42 million years. In the Ordovician, Gondwana, moving south, reached the region of the Southern geographic pole(now in northwestern Africa). The oceanic lithospheric plate Proto-Farallon (and probably the Proto-Pacific plate) was being pushed under the northern margin of the Gondwana plate. The contraction of the Proto-Atlantic depression, located between the Baltic shield, on the one hand, and the united Canadian-Greenland shield, on the other hand, began, as well as a reduction in oceanic space. Throughout the Ordovician, there was a reduction in oceanic spaces and the closure of marginal seas between continental fragments: Siberian, Proto-Kazakhstan and Chinese.

Silurian Silurian period (Silurian, also Silurian system) is a geological period, the third period of the Paleozoic, after the Ordovician, before the Devonian. It began 443.4 ± 1.5 million years ago and ended 419.2 ± 3.2 million years ago. Thus it continued for about 24 million years. resulting relief earth's surface at the end of the Silurian period it became elevated and contrasting, especially on the continents located in the northern hemisphere. The Caledonian folding continued.

Devon Devon (Devonian period, Devonian system) is the fourth geological period of the Paleozoic era. Began 419.2 ± 3.2 million years ago, ended 358.9 ± 0.4 million years ago. Thus it continued for about 60 million years. In the Early Devonian, the Proto-Atlantic Trench closes and the Euro forms. American continent, as a result of the collision Pro. European mainland with Pro. North American in the area of ​​what is now Scandinavia and Western Greenland. In the Devonian, the displacement of Gondwana continues, resulting in the South Pole being in southern region modern Africa, and possibly modern South America.

Carboniferous Stone-Golic period, abbreviated Carboniferous (C) - the penultimate (fifth) geological period of the Paleozoic era. It began 358.9 ± 0.4 million years ago and ended 298.9 ± 0.15 million years ago. Thus it continued for about 60 million years. In the Middle Carboniferous, Gondwana and Euro-America collided. As a result, the new supercontinent Pangea was formed. In the late Carboniferous - early Permian, the Euro collision occurred. The American continent with the Siberian continent, and the Siberian continent with the Kazakhstan continent.

Perm The Permian period (Permian) is the last geological period of the Paleozoic era. Began 298.9 ± 0.15 million years ago, ended 252.17 ± 0.06 million years ago. Thus it continued for about 47 million years. The deposits of this period are underlain by the Carboniferous and overlain by the Triassic. Towards the end of the Paleozoic, in the Permian period, Pangea stretched from south pole to North.

Cambrian Intense prosia occurred on land, a large number of sediments were washed into the seas. The oxygen content in the atmosphere gradually increased. Towards the end of the period, glaciation began, leading to a drop in sea level.

Ordovician Large land masses concentrated closer to the equator. Throughout the period, landmasses moved further and further south. Old Cambrian ice sheets melted and sea levels rose. Most of the land was concentrated in warm latitudes. At the end of the period, a new glaciation began.

Silurian Period of violent volcanic activity and intense mountain building. Began with the Ice Age. As the ice melted, sea levels rose and the climate became milder.

Devonian Rivers carried mountains of sediment into the seas. Vast swampy deltas were formed. Towards the end of the period, sea levels dropped. The climate has warmed and become more extreme over time, with alternating periods of heavy rainfall and severe drought. Vast areas of the continents became waterless.

Carboniferous In the early Carboniferous, shallow coastal seas and swamps spread over vast areas, and an almost tropical climate was established. Huge forests with lush vegetation significantly increased the oxygen content in the atmosphere. Subsequently, it became colder, and at least two major glaciations occurred on Earth.

The Permian Period began with glaciation, which caused sea levels to drop. As Gondswana moved north, the earth warmed up and the ice gradually melted. Laurasia became very hot and dry, and vast deserts spread across it.

Cambrian Animal Kingdom During a grandiose evolutionary explosion, most modern types of animals arose, including microscopic foraminifera, sponges, starfish, sea ​​urchins, sea lilies and various worms. In the tropics, archaeocyaths. built huge reef structures. The first hard-bodied animals appeared; trilobites and brachiopods dominated the seas. The first chordates appeared. Later appeared cephalopods and primitive fish.

Ordovician Fauna: A sharp increase in the number of filter-feeding animals, including bryozoans (sea mats), crinoids, brachiopods, bivalves and graptolites, whose heyday occurred during the Ordovician. Archaeocyaths had already become extinct, but the reef-building baton was picked up from them by stromatoporoids and the first corals. The number of nautiloids and jawless armored fishes has increased.

Flora: Existed different kinds seaweed In the Late Ordovician, the first true land plants appeared.

Silurian Fauna: Nautiloids, brachiopods, trilobites and echinoderms thrive in the seas. The first jawed acanthod fish appeared. Scorpions, millipedes, and possibly eurypterids began to move onto land. The formation of the main classes of invertebrate organisms, the first primitive vertebrates (jawless and fish) appeared.

Devonian Fauna: Rapid evolution of fish, including sharks and rays, lobe-finned and ray-finned fish. The land was invaded by a variety of arthropods, including ticks, spiders and primitive wingless insects. The first amphibians also appeared in the Late Devonian.

Flora: Plants managed to move away from the water's edge and soon vast areas of land were covered with dense primeval forests. The number of diverse vascular plants has increased. Spore-bearing lycophytes (moss mosses) and horsetails appeared, some of them developed into real trees 38 m high.

Carboniferous Fauna: Ammonites appeared in the seas, and the number of brachiopods increased. Rugosas, graptolites, trilobites, as well as some bryozoans, crinoids and molluscs became extinct. It was the age of amphibians, as well as insects - grasshoppers, cockroaches, silverfish, termites, beetles and giant dragonflies. The first reptiles appeared.

Flora: River deltas and the banks of vast swamps are overgrown with dense forests of giant club mosses, horsetails, tree ferns and seed plants up to 45 m high. The undecomposed remains of this vegetation eventually turned into coal.

Perm Fauna: Bivalve mollusks have evolved rapidly. Ammonites were found in abundance in the seas. IN fresh water The lands were dominated by amphibians. Aquatic reptiles also appeared, including mesosaurs. During the great extinction, over 50% of animal families disappeared. On land, reptiles took over amphibians.

Flora: Forests of large seed ferns, Lossopteris, have spread across the southern land masses. The first conifers appeared, quickly populating inland areas and highlands. Among terrestrial plants, arthropodous ferns and gymnosperms predominated.

Conclusion: Paleozoic era (Greek “palaios” - ancient, “zoe” - life) - era ancient life Its age is 570 million years. It is divided into 6 periods (Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian) The plant world developed from algae to the first seed plants (seed ferns) The animal world developed from primitive marine skullless chordates to terrestrial reptiles. In the Silurian period, the first inhabitants of land appeared - psilophyte plants and invertebrate arachnids. These were the first animals to breathe atmospheric oxygen.

The Paleozoic era covers a huge period of time from approximately 542 to 250 million years ago. Its first period was the “Cambrian”, which lasted about 50-70 (according to various estimates) million years, the second was the “Ordovician”, the third was the “Silurian”, the fourth was the sixth, respectively, “Devonian”, “Carboniferous”, “Permian” . At the beginning of the Cambrian, the vegetation of our planet was represented mainly by red and blue-green algae. This variety in its structure is more similar to bacteria, since it does not have a nucleus in the cell (real algae have this nucleus, therefore they are eukaryotes). The Paleozoic era, whose climate at the beginning was temperate, with a predominance of seas and low-lying land, contributed to the prosperity of algae.

It is believed that they created the atmosphere

They came from worms

The Paleozoic era was the time of the birth of the ancestors of modern cephalopods - squids, octopuses, cuttlefish. Then they were small creatures with horny shells, through which a siphon passed, allowing the animal to fill parts of the shells with water or gases, changing its buoyancy. Scientists believe that ancient cephalopods and molluscs descended from ancient worms, the remains of which are few, since they consisted mainly of soft tissue.

The Paleozoic era, in which plants and animals either replaced each other or coexisted side by side for millions of years, also gave birth to cystoids. These creatures, attached to the bottom by a limestone cup, already had tentacle arms that pressed passing food particles to the feeding organs of the cystoid. That is, the animal moved from passive waiting, as in archaeocyaths, to food production. Scientists also attributed the discovered fish-like creature, which had a backbone (notochord), to the Early Paleozoic.

Three-meter-long crustacean scorpions... with a poisonous sting

But primitive fish developed in the Silurian and Ordovician, where they were jawless, shell-covered creatures with organs that emitted electrical discharges for protection. During the same period, you can find giant nautiloids with three-meter shells and no less large crustacean scorpions, up to three meters long.

The Paleozoic era was rich in climate changes. Thus, in the Late Ordovician it cooled significantly, then it warmed up again, in the Early Devonian the sea retreated significantly, and active volcanic mountain building took place. But it is the Devonian that is called the era of fish, since they were very common in water cartilaginous fish- sharks, rays, lobe-finned fish that had nasal openings for breathing air from the atmosphere and could use fins to walk. They are considered the ancestors of amphibians.

The first steceophages (amphibians) giant snakes and lizards) left their traces in the late Paleozoic, where they coexisted with cotilomeres - ancient reptiles that were both predators and insectivores and herbivores. The Paleozoic era, the table of development of life forms during which is presented above, left many mysteries that scientists have yet to solve.

They lived in the seas.

Some animals led sedentary image life, others moved with the flow. Bivalves, gastropods, annelids, and trilobites were widespread and actively moving. The first representatives of vertebrates appeared - armored fish that did not have a jaw. Armored animals are considered the distant ancestors of modern cyclostomes, lampreys, and hagfish.

In mountain sediments, remains of protozoa, sponges, coelenterates, crustaceans, blue-green and green algae characteristic of the Cambrian period were found, as well as spores of plants that grew on land.

IN Ordovician period The areas of the seas expanded, and the diversity of green, brown, red algae, cephalopods and gastropods increased. The formation of coral reefs is increasing, the diversity of sponges, as well as some bivalves, is decreasing.

Climate

IN Silurian period mountain building processes are intensifying, and the land area is increasing. The climate becomes relatively dry and warm. Powerful volcanic processes occurred in Asia. Fossilized imprints of coelenterate animals and a low-growing psilophyte were found in mountain sediments.

Animals

Climate

IN Devonian period The area of ​​seas continues to decrease and the land area increases and divides. The climate becomes temperate. A significant part of the land turns into deserts and semi-deserts.

Animals

Animals

The conditions of the Permian period were extremely unfavorable for amphibians. Most of them died out, this event was called the “Permian Mass Extinction” . Smaller representatives of amphibians took refuge in swamps and shallows. The struggle for existence and natural selection in a dry and more or less cold climate caused changes in separate groups amphibians, from which reptiles then evolved.

Permian mass extinction

A major marine extinction occurred at the Paleozoic–Mesozoic boundary. Its causes can be associated with the success of terrestrial vegetation in terms of soil consolidation. Just shortly before that, drought-resistant conifers appeared, which for the first time were able to populate the inner parts of the continents and reduced their erosion.

The appearance of eukaryotes marked the beginning of the emergence in the Upper Riphean about 1.4–1.3 billion years ago of multicellular plants and animals, which appeared almost simultaneously (Sokolov, 1975).

An increase in oxygen content in the aquatic environment and atmosphere has become a leading environmental factor in the development of life on Earth. It was photosynthetic microscopic algae that predetermined the formation of highly organized life on the planet and the biosphere as a whole.

In the Vendian, between two phases of glaciation, the Ediacaran fauna arose and became widespread, immediately preceding the fauna of skeletal organisms. It was represented by invertebrates: coelenterates and the first organisms with a nervous system – worms. Distinctive feature The Ediacaran fauna is that its representatives did not have skeletons. Although some of them reached sizes of up to 1 m (jellyfish), they consisted of a jelly-like substance, probably enclosed in a denser outer layer. Among them were organisms leading a bottom lifestyle, as well as passively or actively moving in the water column. The amazing preservation of the prints of Ediacaran animals can be explained by the absence of predators, as well as saprophages and ground eaters.

If until the end of the Proterozoic the evolution of life on Earth proceeded extremely slowly, then during the Phanerozoic there were fairly rapid, abrupt changes in the organic world of the planet. Driving force This evolution was still a matter of natural selection, which was determined by the ability of organisms to transform in conditions of limited food resources of the emerging biosphere, as well as changes in physical and geographical conditions. Natural selection has developed the ability of organisms to adapt to dynamic natural environment. Yes, saturation aquatic environment oxygen turned out to be disastrous for most anaerobic representatives of organic life, and only a few species were able to adapt to the new conditions.

Development of life in the Paleozoic

The rapid development of life began in the Paleozoic era, which falls into two stages: early and late. The early stage, including the Cambrian (570–500 million years ago), Ordovician (500–440 million years ago) and Silurian (440–400 million years ago), coincided with the Caledonian tectonic cycle.

The breakup of the early supercontinent, which began at the end of the Proterozoic, led in the Cambrian to the formation of the huge continent of Gondwana, which included modern Africa, South America, India, Australia and Antarctica, as well as to the emergence of the Baltic, Siberian, Chinese and North American microcontinents. Sea transgression at the beginning of the Cambrian gave way to regression in the second half of this period.

In the Cambrian warm seas, the waters of which acquired a chemical composition close to modern ones, blue-green algae developed widely, as evidenced by traces of their vital activity - stromatolites. The flora was also abundantly represented by algae. At the same time, the Cambrian is a time of rapid development of arthropods, especially trilobites; Cambrian sediments preserve the remains of both soft-bodied and hard-bodied animals with an external skeleton (shells). The evolution of skeletal organisms was prepared by the entire evolution of the organic world of the ancient aquatic environment, including the appearance of predators, as well as the transition to living on the bottom and in other probable conditions. From this time on, biogenic sedimentation in OK(U) HC becomes predominant.

The oxygen content in the atmosphere during the Cambrian period reached approximately 1% of modern level. The content decreased accordingly carbon dioxide and possibly water vapor. This weakened the greenhouse effect of the atmosphere and made it more transparent due to decreased cloudiness. The role of sunlight in biological, geochemical and lithological processes began to increase sharply. The moderately warm and dry climate of the Cambrian was characterized by relative diversity, including periods of cooling, up to the formation of glacial deposits.

There is no convincing evidence yet for the existence of any living organisms on land in the Cambrian. Ground higher plants, which would produce spores and pollen, have not yet existed, although the colonization of land by bacteria and blue-green algae is not excluded. Since there are no traces of coal accumulation in Cambrian sediments, it can be argued that there was no abundant and highly organized vegetation on land. Life was concentrated in the shallow waters of epicontinental seas, i.e. seas located on continents.

Skeleton of the Paleozoic period. Photo: Dallas Krentzel

Ancestor of the crocodile from the Paleozoic period. Photo: Scott Heath

At the beginning of the Ordovician, the evolution of the organic world became more intense than in the Cambrian and led to the emergence of new families. During this period, Gondwana continued to exist with the Chinese mainland joining it. Baltic, Siberian and North American microcontinents.

In the first half of the Ordovician, extensive sea transgression occurred, resulting in more than 83% of the surface being under water globe. Almost all modern continents were flooded. The most characteristic sedimentary deposits of this time are biogenic limestones and dolomites - indicators warm climate. In warm seas, trilobites became widespread, replacing the Cambrian chitinous skeleton with a calcareous one. In addition to them and microorganisms (bacteria, blue-green algae and algae), the characteristic animals of the aquatic environment were graptolites, tabulates, brachiopods, echinoderms, archaeocyaths, cephalopods, etc. In the Ordovician, the first vertebrates appeared - jawless fish-like creatures with a two-chambered heart and a simply constructed brain, protected air pericerebral capsule. Further development marine vertebrates followed the path of increasing complexity of the brain (digitalization), the circulatory system and all other organs and systems.

At the end of the Ordovician, regression of the sea began, associated with one of the early phases of the Caledonian folding, which received its greatest development and distribution in the next, Silurian period. This regression was accompanied by climate cooling. In the changed paleogeographic conditions, a mass extinction of representatives of the marine fauna occurred.

Most crises in the development of fauna, both in the Late Ordovician and in previous and subsequent geological periods, coincided with epochs of temperature minimums, and the largest of them coincided with glaciation epochs (Ushakov, Yasamanov, 1984). All other environmental factors are somehow related to climate. The connection between the organic world and climate determined the evolution of the biosphere. Extinction crises were typically followed by periods of extraordinary flourishing of life. Organisms did not just spread, exploring new habitats, their evolution occurred at an increasing speed. It is the unity of organisms and the environment, as one of the fundamental laws of biology, with the increasing capabilities of the organisms themselves, that presupposes the presence of diverse forms of adaptation that arise in the process of the evolution of life on Earth.

In the settlement and development of organisms, as well as in the evolution of the biosphere, the most important role was played by global paleogeographic factors (climate, the relationship between land and sea, the composition of the atmosphere, the presence of areas with a nutrient medium, etc. Conditions were largely determined by the intensity of volcanic activity and tectonic activity Compound continental blocks led to increased seasonality of climate and the appearance of glaciation, and the fragmentation of the lithosphere led to a softening of climatic conditions. At the same time, the initial phases of tectonic activity usually corresponded to a climate with the most pronounced seasonality, which was accompanied by glaciation and aridity. Following this period, increased humidization and aridity began. climate warming, which intensified the development of the biosphere. At the same time, the supply of gases and nutrients from the bowels of the Earth as a result of volcanic activity was of great importance for organic life. For this reason, the development of life and the evolution of the biosphere are largely consistent with the eras of tectonic activity when the main events took place. the collision of lithospheric plates and continental drift, and with existing climatic conditions (Ushakov, Yasamanov, 1984).

The Caledonian orogeny led to significant changes in the distribution of sea and land. Mountain formation occurred in many areas of the planet, in particular, the Scandinavian Mountains, the Eastern and Western Sayans, the Baikal and Transbaikal ranges, etc. arose. The land area increased. Volcanic activity was accompanied by the release of huge amounts of ash and gases, which changed the properties and composition of the atmosphere. In the Silurian, all platforms experienced uplift. Warm seas shallowed, leaving thick layers of limestone and dolomite.

The climate of this period, characterized by aridity, was warm. average temperature air at the surface was more than 20 °C, exceeding the modern one by 6 °C (Bydyko, 1980). The oxygen content in the Silurian atmosphere reached 10% of the modern level. The formation of the ozone screen, which most likely appeared in the Ordovician, continued to form.

The organic world of the Silurian was much richer than that of the Ordovician. Cartilaginous fish appeared in the seas. Under the protection of the ozone screen, which probably acquired a certain reliability, plants spread over the entire water surface and, together with microscopic animals, formed plankton, which served as a food supply or shelter for large organisms. Obviously, plants developed most in lagoon lakes and coastal swamps with desalinated waters. Here a living type of plants appeared, the lower part of which was in water, and the upper part in air environment. Passive movement in the coastal lowlands associated with rough seas, ebbs and flows, led to the fact that some plants and animals that abundantly inhabited coastal waters found themselves in a periodically flooded and drying zone, in which the conditions for amphibian plants differed little from the conditions of shallow marine waters. Having adapted to existence in this zone, sea ​​plants They began to more actively develop the rest of the land.

The first known land plants are Cooksonia, united by paleobotanists under common name rhiniophytes, still somewhat reminiscent of algae. They had no roots (there were only root-like formations) and leaves. A very simply branching, primitive low (up to 50 cm) stem ended in a spore-bearing shoot for reproduction. These plants sometimes formed thickets in shallow coastal waters and in wet, low-lying, swampy, and dry areas around water basins.

Of the animals, they were inhabited by arthropods, worms and vertebrates, the probable ancestors of which, who populated the shallow seas and coasts with desalinated water, adapted to life in an oxygen-nitrogen air environment.

The soil substrate, covered with primary terrestrial vegetation, gradually turned into soil under the influence of bacteria and algae that moved here, processing organic residues.

The development of land by plants was an outstanding event in the evolution of the organic world and the biosphere.

First of all, the sharply increased primary resources provided the conditions for an accelerated, compared to the aquatic environment, process of speciation, which was devoid of intense competition in the first stages of land settlement. In this process, living organisms realized their ability to constantly expand their range and develop new habitats (land, air and fresh water). The evolution of marine fauna in the less sharply changing iodine environment of the Paleozoic and in the later geological period proceeded very slowly.

The Late Paleozoic included the following periods: Devonian (-100–345 million years ago), Carboniferous (345–280 million years ago) and Permian (280–235 million years ago). This stage was characterized by a wide distribution of terrestrial plants and animals. Land became the main arena for the development of life on Earth.

The ongoing Caledonian orogeny and the early stages of the Hercynian folding, together with the movement of lithospheric plates, led to further restructuring of the lithosphere; in the Early and Middle Devonian, a single Pangea already existed, separated from the Siberian microcontinent by the Ural Ocean.

The decrease in the level of the World Ocean was accompanied by a complication of the topography of its bottom. Perhaps the basin was founded at this time Pacific Ocean. The low level of the World Ocean remained until the next geological period - the Carboniferous.

The increased area of ​​the continents significantly exceeded the area of ​​the sea basins; 70% of the modern oceans were occupied by land.

At the beginning of the Devonian, low (1–2 m) extensive thickets of psilophytes, the evolutionary descendants of rhinophytes, became an integral component of marshy areas. The saline habitats were then colonized by zosterophylls, also low-growing plants. Over 60 million years, under conditions of a predominantly hot but humid climate, an air environment saturated with carbon dioxide as a result of active volcanic activity, the green cover on the marshy shores and desalinated shallow waters of warm seas has changed; low-growing thickets of primitive plants replaced forests of proto-gymnosperms.

During the Devonian, the first ferns, horsetails and mosses appeared, and the ancient fern (Archaeopteris) flora replaced the psilophyte flora. Forests of tree ferns appeared along sea coasts, in shallow bays and marshy lagoons with muddy bottoms. The fern trunk at the base reached 2 m, the crown was crowned with snail-twisted young branches (eospermatoteris, archaeopteris). The terminal branches of primitive ferns such as Ptilophyton were flattened (the first stage of the formation of true leaves). Under the canopy of tree ferns, related low-growing ferns huddled, horsetails became common, and moist places were occupied by ancient mosses and mosses (asteroxylon and schizopodium).

The development of living space on land continued, but until the middle of the Devonian it happened rather slowly. In the Late Devonian, forests occupied a significant part of the land, reducing surface runoff from the continents and thereby reducing erosion. The rainwater runoff from the land was replaced by the formation of linear river systems. The supply of terrigenous matter to the ocean has sharply decreased. The water in the seas has become clearer, the area illuminated by the Sun has increased, and the biomass of phytoplankton has increased. In addition to rivers, permanent freshwater bodies of water – lakes – arose on the surface of the continents. The main result of the ongoing processes was that with the formation of vegetation on land, the biosphere acquired a powerful resource-generating and stabilizing factor.

The reduction in the area of ​​the ocean and changes in its aquatic environment led to some short-term decline in the development of the organic world. In the Devonian seas, the number of trilobites and graptolites sharply decreased, and fish arose and rapidly developed. Some of them (arthrodires) turned into fast-swimming predators of quite large sizes.

Freshwater lakes and rivers were inhabited by the ancestors of terrestrial vertebrates - lobe-finned fish, which had light and paired fins, from which five-fingered limbs could arise.

Ancient representatives of land vertebrates developed problems associated with finding food, reproduction and breathing. The search for food required the improvement of physical support organs, which could not but affect the development and strength of the skeleton. However, vertebrates could not yet completely leave the aquatic environment, because in dry conditions their reproductive cells were subject to drying out.

The difference in the ratio of free oxygen and carbon dioxide in the air and in the aquatic environment contributed to the improvement of the respiratory apparatus.

Such vertebrates colonizing land could only be amphibians (amphibians), descended from lobe-finned fish. Scaled bodies with strong bones, four limbs and long tail, ending in a fin, allowed the first inhabitants of land - labyrinthodonts - to lead an aquatic and terrestrial lifestyle. Eyes on the top of the head and sharp teeth allowed these first crocodile-like amphibians to navigate their natural environment.

The increasing aridity and continentality of the climate in the Devonian led to the rapid drying out of fresh water bodies, causing mass death of their inhabitants. The continental sediments of this time, ancient red sandstones, contain entire “fish layers”, which made it possible to call the Devonian the “age of fish”.

The end of the Devonian was marked by a new transgression of the sea, as well as an increase in the oceanic climate. The land area gradually decreased, preceding a new grandiose restructuring of the biosphere.

The Carboniferous, or Carboniferous, period was a period of rapid development of vegetation on all continents and the formation of thick layers in many places on the planet coal(Ukraine, China, Indonesia, Western Europe, North America). At the beginning of the Carboniferous, transgression of the sea continued, as a result of which the land area was reduced to 96 million square meters. km, became 35% less than the modern value (149 million sq. km). In particular, large areas of Europe were under the sea. Warm Carboniferous seas left strata of organogenic and chemogenic limestones.

In the second half of the Carboniferous period, the most powerful phase of the Hercynian orogeny, which continued in Perm, led to the emergence of folded mountains of Central Europe, the North Caucasus and Ciscaucasia, the Tien Shan, the Urals, Altai, the Appalachians, the South American Andes, the North American Cordillera, Mongolia , Canadian Arctic Archipelago, etc.

Activation of mountain-building movements earth's crust in the second half of the Carboniferous, it was accompanied by a long-term regression of the ocean and an increase in land area. As a result of the continuous slow movement of lithospheric plates and the Hercynian orogeny, the previously separated parts merged again. With the emergence of new ridges and the retreat of the sea, the relief of the continents became elevated and highly dissected. The average height of the continents also increased. Along with the existing Gondwana, which united Australia, India, Arabia, South America and Antarctica, an equally huge Laurasia was formed on the planet as a result of a significant increase in the area of ​​the North American continent, Europe, the Chinese and Siberian platforms, as well as the formation of land in the North Atlantic. Laurasia was a supercontinent that almost surrounded the Arctic basin. Only Western Siberia remained the seabed. Between Laurasia and Gondwana is the Mediterranean Tethys Ocean. The oxygen content in the Carboniferous atmosphere remained approximately at the modern level. The rapid development of vegetation led to a decrease in the proportion of carbon dioxide in the air to 0.2% in the second half of the Carboniferous. During almost the entire period, a warm, waterlogged climate prevailed. The average air temperature at the beginning of the Carboniferous was 25.6°C (Budyko, 1980), which did not exclude glaciation on almost all continents of the Southern Hemisphere.

In the Early Carboniferous, the Eurasian and Angara, or Tunguska, phytogeographic regions became isolated in Laurasia. In the humid tropical and equatorial climate of the Eurasian region, which included Europe, North America, North Africa, the Caucasus, Central Kazakhstan, Central Asia, China and Southeast Asia, dominated by multi-tiered forests of tall (up to 30 m) plazgns with a branched crown and psaronius ferns with large feathery leaves. Calamite horsetails and cuneate leaves also gave these forests their originality. If the height of calamites reached 10, less often 20 m, then the clinoliths had lodging or creeping stems several meters long. In a warm and constantly humid climate, the wood did not have annual rings of radial growth. Green carbon-forming algae abounded in fresh waters. The gloomy world of forest swamps was complemented by stegocephals and amphibians; reptiles were still rare. Mayflies and dragonflies soared in the air, reaching gigantic sizes (wingspan up to 70 cm), and arachnids were also widespread. In general, the Carboniferous is characterized by a flourishing of insects.

To the north, in the Angara region (Siberia, Eastern Kazakhstan, Mongolia), the dominant lycophytes were replaced by fern-like and cordaites in the Middle and Late Carboniferous. The cordaite “taiga” was characterized by tall (over 30 m) trees with a trunk with annual rings and a network of roots that went into the swampy soil. Their branches ended in long (up to 1 m) linear leaves. The cordaite “taiga” conquered flat areas with a continental climate and seasonal temperature changes.

In the Gondwana region with moderately warm and humid climate Glossopteris, or Gondwana, small-leaved flora, devoid of tree ferns, developed. By the end of the Carboniferous, due to continental glaciation, the woody vegetation of Gondwana was replaced by shrubs and herbaceous ones. Under changing climatic conditions, seed ferns (pteridosperms) and the first gymnosperms – cycads and bennettites, which, like cordaites, were more adapted to the changing seasons, acquired an evolutionary advantage. Seeds supplied with a supply of nutrients and protected by a shell from adverse effects natural conditions, performed the task of propagating and distributing plants much more successfully. It should be noted that cycads have survived to this day. These are common plants of tropical and subtropical forests.

The fauna of the Carboniferous was marked by the appearance of the first reptiles (reptiles), which, in their biological organization, were much better adapted to living on land than their amphibian ancestors. In the history of vertebrate development, reptiles became the first animals that reproduced by laying eggs on land and breathed only through their lungs. Their skin was covered with scales or scutes.

Despite the progressive development of the integument, respiratory and circulatory organs, reptiles did not provide themselves with a warm-blooded body, and their body temperature, like that of amphibians, depended on temperature environment. This circumstance later played a major role in their evolution. The first reptiles - cotilosaurs - were massive animals ranging in size from several tens of centimeters to several meters, moving on thick five-fingered limbs. More mobile forms of reptiles evolved from them, while the cranial shell inherited by the latter was reduced, the limbs lengthened, and the skeleton became lighter.

Permian period

The Hercynian orogeny ended in the middle of the next geological period - the Permian. In the Permian, a single Pangea continued to exist, stretching from the South to the North Pole. Compression of the Hercynian Ural-Appalachian belt and further movement of lithospheric plates led to the formation mountain systems. The high mountain systems created by the Hercynian orogeny and, mainly, the gigantic land area contributed to the loss of heat by the biosphere. The Earth's average air temperature dropped by 3–4 °C, but remained 6–7 °C higher than today. Low temperature values ​​indicated ongoing planetary cooling associated with the Upper Paleozoic (Permo-Carboniferous) glaciation of Gondwana. In the Northern Hemisphere, glaciation probably had a local, mountainous manifestation. The chemical composition, structure and circulation of the atmosphere approached modern ones; in general, the Permian climate was characterized by pronounced zonality and increasing aridity. Wet belt tropical climate, confined to the Tethys Ocean, was located within belts of hot and dry climate, with which the deposition of salts and red-colored rocks was associated. To the north and south were humid temperate zones with coal accumulation. The subpolar cold regions became distinctly distinct.

Reduction of evaporating ocean surface by more than 30 million square meters. km, as well as the withdrawal of water for the formation of continental ice sheets led to a general aridization of the climate and the development of desert and semi-desert landscapes. An increase in land area increased the role of terrestrial plants in the evolution of the biosphere. In the middle of the Permian, a powerful stream of glossopteris flora of Gondwana formed, rushing through Hindustan and tropical Africa to Europe and Asia. The East European Platform, like other land areas in the Northern Hemisphere, under conditions of climate aridization, became an arena for the evolutionary struggle of the dying Eurasian and viable Gondwanan floras. A variety of ferns and preserved moss sigillaria formed more or less dense thickets on the coasts of shallow lagoons and swampy areas. In the north of Laurasia, the cordaite “taiga” flourished. The richness of vegetation favored coal accumulation.

By the end of the Permian, some previously widespread plant groups, most notably the tree mosses and cordaites, became extinct. More and more they were replaced by true gymnosperms - conifers, ginkgos, bennettites and cycads. Significant role in the formation of vegetation cover under conditions temperate climate the mosses played.

Rich and varied animal world The seas underwent significant changes by the end of the Permian. The reduction of the aquatic environment led to a great extinction of marine fauna. Many groups of crinoids and urchins, trilobites, rugoses, and a number of cartilaginous, lobe-finned, and lungfishes became extinct.

Terrestrial vertebrates were represented by amphibians and reptiles. Stegocephalians, which predominated among amphibians, mostly died out at the end of the Permian. Along with primitive reptiles - cotylosaurs, reptile beasts became widespread.

 hell)"ez-toc-section" id="_419_359">an class="ez-toc-section" id="_444_419">an class="ez-toc-section" id="_485_444"> class= "ez-toc-section" id="_542_485">Terozoic (1 billion - 542 million years ago), and then replaced (252-66 million years ago). The Paleozoic had a duration of about 290 million years; it began approximately 542 million years ago and ended approximately 252 million years ago.

The beginning of the Paleozoic era is marked by the Cambrian explosion. This relatively rapid period of evolution and species development produced many new and more complex organisms than Earth had ever seen. During the Cambrian, many ancestors of today's species appeared, including and.

The Paleozoic era is broken down into six main periods, presented below:

Cambrian period, or Cambrian (542 - 485 million years ago)

The first period of the Paleozoic era is known as. Some species of ancestors of living animals first appeared during the Cambrian explosion, in the early Cambrian. Although this "explosion" took millions of years, it is a relatively short period of time compared to the entire history of the Earth. At this time, there were several continents that were different from those that exist today. All the land that made up the continents was concentrated in the southern hemisphere of the Earth. This allowed the oceans to occupy vast areas, and sea ​​life thrive and differentiate at a rapid pace. Rapid speciation has resulted in levels of genetic diversity in species that have never before existed in the history of life on our planet.

Almost all life in the Cambrian period was concentrated in the ocean. If there was any life on land, it was most likely single-celled microorganisms. In Canada, Greenland and China, scientists have discovered fossils belonging to this time period, among which many large carnivores similar to shrimp and crabs have been identified.

Ordovician period, or Ordovician (485 - 444 million years ago)

After the Cambrian period came. This second period of the Paleozoic era lasted about 41 million years and increasingly diversified aquatic life. Large predators, similar to, hunted small animals on the ocean floor. During the Ordovician, many environmental changes occurred. Glaciers began to move across continents, and ocean levels dropped significantly. Combination of temperature change and loss ocean water led to which marked the end of the period. About 75% of all living things became extinct at that time.

Silurian period, or Silurian (444 - 419 million years ago)

After the mass extinction at the end of the Ordovician period, the diversity of life on Earth should have rebounded. One of the major changes in the planet's land layout was that the continents began to join together. This created even more continuous space in the oceans for development and diversification. Animals could swim and feed close to the surface, something that had not happened before in the history of life on Earth.

Many different species of jawless fish spread and even the first ray-finned fish appeared. While terrestrial life was still absent (except for solitary cell bacteria), species diversity began to recover. Oxygen levels in the atmosphere were almost the same as today, so by the end of the Silurian period, some species of vascular plants, as well as the first arthropods, were seen on the continents.

Devonian period, or Devonian (419 - 359 million years ago)

Diversification was rapid and widespread during the . Ground flora became more widespread and included ferns, mosses and even seed plants. The root systems of these early land plants helped rid the soil of rocks, providing more opportunities for plants to take root and grow on land. Many insects also appeared during the Devonian period. Towards the end of the Devonian, amphibians moved to land. As continents connected, this allowed new land animals to spread easily into different ecological niches.

Meanwhile, in the oceans, jawless fish adapted to new conditions, developing jaws and scales like modern fish. Unfortunately, the Devonian period ended when large asteroids hit the Earth. The impact of these meteorites is believed to have caused a mass extinction event that wiped out nearly 75% of aquatic species.

Carboniferous period, or Carboniferous (359 - 299 million years ago)

Again, this was a time when species diversity was about to recover from the previous mass extinction. Because the Devonian mass extinction was largely confined to the oceans, land plants and animals continued to thrive and evolve at a fast pace. adapted even further and diverged from the early ancestors of reptiles. The continents were still joined together, and the southernmost regions were once again covered with glaciers. However, there were also tropical climate conditions that allowed for the development of large, lush vegetation that evolved into many unique species. These were swamp plants that formed the coal used today for fuel and other purposes.

With regard to life in the oceans, the pace of evolution appears to have been markedly slower than before. Species that managed to survive the last mass extinction continued to evolve and form new, similar species.

Permian period, or Permian (299 - 252 million years ago)

Finally, all the continents on Earth came together completely to form a supercontinent known as Pangea. At the beginning of this period, life continued to evolve and new species emerged. Reptiles became fully formed, splitting off from the evolutionary branch that eventually gave rise to mammals in the Mesozoic era. Fish from the salty waters of the oceans adapted to live in freshwater bodies throughout the continent of Pangea, leading to the emergence of freshwater animals. Unfortunately, this time of species diversity came to an end, partly due to many volcanic explosions that depleted oxygen and affected the planet's climate, blocking sunlight, which led to the appearance of many glaciers. All this led to the largest mass extinction in Earth's history. It is believed that at the end of the Paleozoic era, almost 96% of all species were destroyed.