Characteristics of the Paleozoic era and its periods. Paleozoic Permian mass extinction

Paleozoic era: Cambrian period (from 540 to 488 million years ago)

This period began with an astonishing evolutionary explosion, during which representatives of most of the main groups of animals known to modern science first appeared on Earth. The boundary between Precambrian and Cambrian is marked by rocks that suddenly reveal an astonishing variety of animal fossils with mineral skeletons - the result of the "Cambrian explosion" of life forms.

In the Cambrian period, large expanses of land were occupied by water, and the first supercontinent Pangea was divided into two continents - northern (Laurasia) and southern (Gondwana). There was significant erosion of the land, volcanic activity was very intense, the continents sank and rose, resulting in the formation of shoals and shallow seas, which sometimes dried out for several million years and then filled with water again. At this time, the oldest mountains appeared in Western Europe (Scandinavian) and central Asia (Sayans).

All animals and plants lived in the sea, however, the intertidal zone was already inhabited by microscopic algae, which formed terrestrial algal crusts. It is believed that the first lichens and terrestrial fungi began to appear at this time. The fauna of that time, first discovered in 1909 in the mountains of Canada by C. Walcott, was represented mainly by bottom organisms, such as archaeocyaths (analogues of corals), sponges, various echinoderms (starfish, sea urchins, sea cucumbers, etc. ), worms, arthropods (various trilobites, horseshoe crabs). The latter were the most common form of living creatures of that time (approximately 60% of all animal species were trilobites, which consisted of three parts - a head, a torso and a tail). All of them died out by the end of the Permian period; of the horseshoe crabs, only representatives of one family have survived to this day. Approximately 30% of Cambrian species were brachiopods - marine animals with bivalve shells, similar to mollusks. From trilobites that switched to predation, crustacean scorpions up to 2 m long appear. At the end of the Cambrian period, cephalopods appeared, including the genus of nautiluses, which is still preserved, and from echinoderms - primitive chordates (tunicates and anesculates). The appearance of the notochord, which gave rigidity to the body, was an important event in the history of the development of life.

Paleozoic era: Ordovician and Silurian periods (from 488 to 416 million years ago)

At the beginning of the Ordovician period, most of the southern hemisphere was still occupied by the great continent of Gondwana, while other large land masses were concentrated closer to the equator. Europe and North America (Laurentia) were pushed further apart by the expanding Iapetus Ocean. At first, this ocean reached a width of about 2000 km, then began to narrow again as the land masses that make up Europe, North America and Greenland began to gradually approach each other until they finally merged into a single whole. During the Silurian period, Siberia “swimmed” to Europe (the Kazakh small hills were formed), Africa collided with the southern part of North America, and as a result, a new giant supercontinent Laurasia was born.

After the Cambrian, evolution was characterized not by the emergence of completely new types of animals, but by the development of existing ones. In the Ordovician, the most severe flooding of land in the history of the earth occurred, as a result, most of it was covered with huge swamps; arthropods and cephalopods were common in the seas. The first jawless vertebrates appear (for example, the current cyclostomes - lampreys). These were bottom forms that fed on organic remains. Their body was covered with shields that protected them from crustacean scorpions, but there was no internal skeleton yet.

Approximately 440 million years ago, two significant events occurred at once: the emergence of plants and invertebrates onto land. In the Silurian there was a significant rise of land and a retreat of ocean waters. At this time, lichens and the first land plants resembling algae - psilophytes - appeared along the swampy shores of reservoirs, in the tidal zones. As an adaptation to life on land, an epidermis with stomata, a central conducting system, and mechanical tissue appear. Spores with a thick shell are formed, protecting them from drying out. Subsequently, the evolution of plants went in two directions: bryophytes and higher spore-bearing plants, as well as seed-bearing plants.

The emergence of invertebrates onto land was due to the search for new habitats and the absence of competitors and predators. The first terrestrial invertebrates were represented by tardigrades (which tolerate drying well), annelids, and then millipedes, scorpions and arachnids. These groups arose from trilobites that often found themselves on the shallows during low tides. In Fig. Figure 3 presents the main representatives of animals of the early Paleozoic.

Rice. 3. Early Paleozoic: 1-archaeocyaths, 2,3-coelenterates (2-four-rayed corals, 3-jellyfish), 4-trilobite, 5,6-mollusks (5-cephalopods, 6-gastropods), 7-brachiopods, 8, 9-echinoderms (9-crinoids), 10-graptolite (hemachordates), 11-jawless fishes.

The Paleozoic era is a geological period that began 541 million years ago and ended 252 million years ago.

It is the first in the Phanerozoic eon. It was preceded by the Neoproterozoic era, and will be followed by the Mesozoic era.

Periods of the Paleozoic era

The era is quite long, so scientists decided to divide it into more convenient segments - periods based on stratigraphic data.

There are only six of them:

Cambrian,
Ordovician,
Silurian,
Devonian,
carbon,
Permian.

Processes of the Paleozoic era

During the Paleozoic era, large and small changes occurred in the appearance of the earth, its development, and the formation of flora and fauna.

Palaeozoic. Cambrian period photo

There was an intensive formation of mountains and mountain ranges, the activity of existing volcanoes was noted, cold temperatures and heat changed all the time, the level of seas and oceans increased and decreased.

Characteristics of the Paleozoic era

The beginning of the Paleozoic era was marked by the Cambrian explosion, or a sharp increase in the number of living things. Life took place mainly in the seas and oceans and was just beginning to move to land. Then there was one supercontinent - Gondwana.

Palaeozoic. Ordovician period photo

By the end of the Paleozoic, significant changes occurred in the movement of tectonic plates. Several continents merged to form a new supercontinent - Pangea.

Palaeozoic. Silurian period photo

The era ended with the extinction of almost all living things. It is one of the 5 great extinctions on the planet. During the Permian period, up to 96% of living organisms in the world's oceans and up to 71% of terrestrial life died out.

Life in the Paleozoic era

Life was beyond varied. Climates replaced each other, new forms of life developed, for the first time life “moved” to land, and insects mastered not only the aquatic and terrestrial environment, but also the air, learning to fly.

Flora in the Paleozoic era developed rapidly, as did the fauna.

Plants of the Paleozoic era

In the first two periods of the Paleozoic era, the plant world was represented mainly by algae. During the Silurian period, the first spore plants appear, and at the beginning of the Delurian there are already many simple plants - rhiniophytes. By the middle of this period, vegetation develops.

Palaeozoic. Devonian period photo

The first lycophytes, proto-ferns, arthropods, progymnosperms, and gymnosperms appeared. Soil cover develops. Carboniferous marked the appearance of horsetail-like, tree-like platsnovae, ferns and pteridophytes, cordaites. Carboniferous flora eventually formed a thick layer of coal, which is still mined today.

Animals of the Paleozoic era

During the entire Paleozoic era, all species of animals appeared and formed on the planet, with the exception of birds and all mammals. At the beginning of the Cambrian, an incredibly large number of creatures with a hard skeleton appeared: acritarchs, archaeocyaths, brachiopods, gastropods, bivalves, bryozoans, stromatoporoids, chiolites, chiolithelminths.

Palaeozoic. Carboniferous period photo

Trilobites, the oldest form of arthropods, became widespread. There were many invertebrate graptolites and cephalopods. In the Devonian period, goniptites appeared - a more complex form of invertebrates. And in the late Paleozoic, foraminifera formed.

In the Paleozoic, land was inhabited by centipedes, spiders, ticks, scorpions and various insects. In the Cambrian, gastropods appeared that could breathe with lungs. Some flying insects are also known. Aromorphoses of the Paleozoic era During the Paleozoic, significant changes occurred in the formation of life on the planet.

Palaeozoic. Permian period photo

In the Cambrian, animals had a predominantly calcareous or phosphate skeleton, predators predominated, and moving organisms began to develop. Animals still continue to develop. Silurian marked the appearance of the first arthropods, a new order of invertebrates - echinoderms and vertebrates. The simplest land plants also evolved.

The Devonian period marked the beginning of the reign of fish. Some animals develop lungs - amphibians appear. At this time, mosses, mosses, horsetails and ferns developed. In the Carboniferous, insects learned to fly, and gymnosperms began to spread.

Palaeozoic. periods of photo development

By the end of the Permian period, the pulmonary system of some animals became significantly more complex, and a new type of skin appeared - scales.

Climate of the Paleozoic era

At the beginning of the period under review, the Earth was warm. A tropical climate prevailed on all land territories; the temperature in the seas and oceans did not drop below 20 degrees Celsius. In the next two periods, the climate changes significantly.

There are five climate zones:

equatorial,
tropical,
subtropical,
moderate,
nival.

Towards the end of the Ordovician, cold weather began. Temperatures in the subtropics dropped by 10-15 degrees, and in the tropics by 3-5 degrees. In the Silurian, the climate returned to normal - it became warmer. The increase in vegetation led to abundant photosynthesis. The formation of Pangea led to the fact that for some time there was practically no precipitation at all. The climate was dry and temperate. But it soon began to get colder.

In the late Carboniferous and early Permian, ice covered the entire northern part of Pangea. The end of the era brought warmth, and the zone of the tropics and equatorial zone expanded. The water temperature has increased significantly.

There is some evidence that higher land plants already existed in the Cambrian and Ordovician, but scientists have not yet reached a consensus on this matter, so this is only an unconfirmed theory.
The sizes of Paleozoic insects were not entirely standard. So the wingspan of an ordinary dragonfly was a meter! Centipedes reached 2 meters! It is believed that insects reached such sizes due to the abundance of oxygen in the air. In the Late Carboniferous, the formation of different climatic zones, which are known to this day, took place.
The Paleozoic era brought many changes to the planet. Climates and continents changed, mountains and seas were formed. This is the time of development of new forms of life. Some of them still exist today, but in much smaller sizes and in greater variety.

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 South Geographic Pole (now the northwestern part of 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. As a result, the relief of the earth's surface at the end of the Silurian period 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, as a result, the South Pole ends up in the southern region of modern Africa, and possibly present-day 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, Gondwanaland 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 sediments of this period are underlain by the Carboniferous and overlain by the Triassic. By the end of the Paleozoic, in the Permian period, Pangea stretched from the South Pole to the North Pole.

Cambrian Intense prosia occurred on land, large amounts of sediment 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, land masses 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 A grand evolutionary explosion produced most of the modern animal phyla, including microscopic foraminifera, sponges, starfish, sea urchins, crinoids, 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, cephalopods and primitive fish appeared.

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: There were various types of algae. 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, centipedes, 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. Amphibians dominated in fresh water bodies. 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 landmass. The first conifers appeared, quickly populating inland areas and highlands. Among terrestrial plants, arthropodous ferns and gymnosperms predominated.

Conclusion: The Paleozoic era (Greek “palaios” - ancient, “zoe” - life) is the era of 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 crayfish 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 cartilaginous fish were very common in the water - sharks, rays, lobe-finned fish, which had nasal openings for breathing air from the atmosphere and could use fins for walking. They are considered the ancestors of amphibians.

The first steceophages (amphibian giant snakes and lizards) left their traces in the late Paleozoic, where they coexisted with cotilomeres - ancient reptiles that were both predators and insectivorous and herbivorous animals. 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 a sedentary lifestyle, 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

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 certain groups of 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.