Paleozoic aromorphoses of plants and animals. Development of life in the Paleozoic era

To understand the evolution of life and the environmental conditions in which its most important events took place, it is important to have a clear understanding of the main stages of the geological history of the Earth and the co-evolution of plant and animal life.

All geological history The earth is divided into eras, and those, in turn, into periods.

The names of eras are Greek (for example, Proterozoic - era early life). The names of the periods reflect either the names of the places where fossil remains of ancient plants and animals of this period were first discovered (for example, the Jurassic period of the Paleozoic era comes from the name of the Jura mountain range in the south of France), or other features of the period (for example, the formation of coal reserves in the Carboniferous period).

Catarchaea and Archaea(ancient era)

Katarhey(era later than the oldest) 5 billion years so-called begins the emergence of the Earth as a celestial body.

3.5 billion years so-called (by geological standards extremely quickly) the first living cells appear on Earth. With the emergence of the first living organisms, the most ancient era - the Archean - begins. In the archaea, 3 generations of prokaryotes sequentially arise - anaerobic bacteria, photosynthetic bacteria and aerobic bacteria (or oxidizers) and, accordingly, the most important biochemical processes: anaerobic respiration (or glycolysis), photosynthesis and, finally, aerobic, or oxygen, respiration.

At the end of the Archean, 2 billion years ago, as a result of the symbiosis of 3 types of prokaryotes, the first eukaryotic cells appeared. In this case, anaerobic prokaryotes give rise to the main carrier cell, photosynthetic bacteria turn into chloroplasts, and oxidizing bacteria turn into the energy stations of the cell - mitochondria.

Thus, the archaea ends with the appearance of the first eukaryotic cells.

The largest aromorphoses of the Archaea are the emergence of life, the appearance of prokaryotic cells, the emergence of photosynthesis, oxygen-free and oxygen respiration, the appearance of the first eukaryotic cells.

Proterozoic(early life era) 2 billion-600 million years so-called (2 billion-590 million years ago)

In the Proterozoic, life in both the plant and animal kingdoms developed only in water. Eukaryotes are developing rapidly. About 1.5 billion years so-called. from the first primitive eukaryotes arises common ancestor plants and animals - an ancient flagellate. By modern ideas flagella, as well as mitochondria and chloroplasts, originated from some ancient free-living prokaryotes.

From the ancient flagellate, two most important kingdoms of living organisms arise - plants and animals.

The evolution of plants is aimed at the transition from unicellular mobile forms to unicellular immobile ones, and then to multicellular immobile forms - filamentous and lamellar algae. The loss of mobility by plants during the process of evolution is associated with their complete transition to autotrophic nutrition through photosynthesis and the loss of the ability for heterotrophic nutrition. Algae that appeared at the end of the Proterozoic are lower plants that do not have differentiated organs and tissues.

The evolution of animals in the Proterozoic proceeds at a much faster pace. Unlike plants, animals in the process of evolution lose chloroplasts and completely switch to heterotrophic nutrition (i.e. feeding on ready-made organic substances). Due to the need to actively search for food sources, animals not only do not lose mobility, but, on the contrary, improve the musculoskeletal system and the mechanisms that control movement.

From unicellular motile forms, motile colonial flagellates first arise - single-layer animals that do not have differentiated organs and tissues, then 2-layer and 3-layer animals with differentiated tissues (3 germ layers will subsequently give rise to various types tissues and in humans). From the middle germ layer, which first appeared in primitive flatworms, muscles and supporting tissues associated with active movement develop.

The last 50 million years of the Proterozoic - Vendian - a period of very rapid development of the animal world: during this period all types of invertebrate animals appeared, with the exception of chordates, including sponges, coelenterates, arthropods, and mollusks.

The largest aromorphoses of the Proterozoic were the emergence of multicellularity (about 1 billion years ago), diploidity and the sexual process. Animals develop differentiated organs and tissues, and a musculoskeletal and nervous system emerges.

The rapid evolutionary progress of animals is associated with their complete transition to heterotrophic nutrition and the need for improvement arising in connection with this musculoskeletal system and managing its work nervous system.

Plants in the Proterozoic transition from unicellular motile forms to unicellular immobile forms, and then to multicellular immobile forms. However, all Proterozoic plants are lower plants (algae) that do not have differentiated organs and tissues.

The largest aromorphoses of the Proterozoic were the emergence of the plant kingdom and the animal kingdom. The emergence of multicellularity and the sexual process in plants and animals. Appearance of all types of invertebrates.

Paleozoic(era of ancient life) 600-250 million years so-called (590-248 million years ago)

The Paleozoic era is one of the most turbulent in the history of the development of life on Earth. During the Paleozoic, major evolutionary changes occurred in both the plant and animal kingdoms.

The Paleozoic is divided into 6 periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian.

Cambrian 600-500 million years so-called (590-505 million years ago)

The Cambrian climate was temperate, the continents were lowland.

In the Cambrian, life developed almost exclusively in water. On land only bacteria and blue-green algae live. Thanks to their activity, soil formation begins, which prepares the way for multicellular plants and animals to reach land.

This is the time of pacifeema algae and invertebrates. Most scientists believe that it was in the Cambrian that the first primitive chordates such as the lancelet appeared.

The largest aromorphosis of the Cambrian was the appearance of the first primitive chordates.

Ordovician 500-450 million years so-called (505-438 Ma so-called)

The Ordovician climate is mild, the seas are shallow. The continents are mostly flat. The area of ​​the seas increased compared to the Cambrian.
In the Ordovician, as in the Cambrian, life developed mainly in water.

The plant kingdom is represented by algae.

The most important event in the animal kingdom is the progressive development of chordates. From primitive chordates such as the lancelet, chordates with a cartilaginous skeleton arise, resembling representatives modern class cyclostomes - lampreys and hagfish, and then jawless armored "fish" - shieldfish. By type of feeding, scutes were filter feeders.

It is believed that in the Ordovician, about 450 million years ago, heterogeneous algae of the caleochaete type appeared on land, which became the ancestors of the first vascular plants - rhiniophytes.

The largest aromorphosis of the Ordovician was the appearance of chordates with a cartilaginous skeleton (scutellates).

Silur 450-400 million years so-called (438-408 million years so-called)

As a result of intensive mountain-building processes in the Silurian, the land area increases significantly. Compared to the Ordovician, the climate becomes drier.

In the Silurian, about 430 million years ago, the first vascular plants appeared on land - rhinophytes (or psilophytes).The body of rhinophytes did not yet have differentiated organs - they had neither leaves nor roots, photosynthesis was carried out by bare leafless stems. However, in connection with reaching land, rhinophytes develop well-developed integumentary and conductive tissues.

In Siluria, not only plants, but also animals come to land for the first time. These are representatives of the type of arthropods - arachnids, externally resembling scorpions. Arthropods were the first animals to reach land because they already had formed walking limbs and an external skeleton, which supported the body and protected it from drying out.

In the Silurian, the most important aromorphosis of animals such as chordates also occurred - in freshwater bodies of water, the first jawed fishes appeared from jawless chordates with a cartilaginous skeleton.

The largest aromorphoses of the Silurian are the emergence of plants (rhiniophytes) and animals (arthropods) onto land; appearance of jawed fish.

Devonian 400-350 million years so-called (408-360 Ma so-called)

In the Devonian, land uplift occurs. The area of ​​the seas is shrinking. The climate is becoming even drier. Desert and semi-desert areas appear.

At the beginning of the Devonian another thing happens an important event in the plant kingdom - about 370 million years so-called. mosses appear.

Some reservoirs in Devon dry up, and fish are forced to either hibernate and breathe through their lungs during this period ( lungfish), or crawl overland into another body of water (lobe-finned fish). The evolutionary progress of chordates is associated with the latter direction of development. Lobe-finned fish turned out to be able to move on land, because due to the bottom-dwelling lifestyle associated with a lack of oxygen, they had already developed light and fleshy fins for moving along the bottom of the reservoir.

By the end of the Devonian, the first amphibians, stegocephalians, emerged from lobe-finned fish.

The largest aromorphoses of the Devonian: in the plant kingdom - the appearance of pteridophytes (ferns, horsetails and mosses), mosses and gymnosperms; in the animal kingdom - the appearance of lobe-finned fish and the first amphibians - stegocephalians.

Carbon (Carboniferous period) 350-300 million years so-called (360-286 million years ago)

In the Carboniferous, the climate becomes humid and warm. Seasonal temperature variations are small. A significant part of modern continents is flooded with shallow seas. In a humid and warm climate, higher spore-bearing (fern-like) plants - ferns, horsetails, and mosses - reach exceptional flowering. Over vast areas, they form swampy forests dominated by tree-like lycophytic lipidodendrons (up to 40 m high), tree ferns (20-25 m high) and giant horsetails - calamites (8-10 m high). Coal reserves are later formed from the dead trunks of these trees.

In humid and warm climates, the main disadvantages of spore plants - water-related reproduction and a free-living gametophyte poorly adapted to exist in arid conditions - are not important. At the same time, small, light spores, unlike heavy gymnosperm seeds, are well transported by the wind. Therefore, although gymnosperms appeared in the Devonian, in the Carboniferous period it was not gymnosperms that dominated, but spores.Along with spore-bearing “amphibious” plants, whose reproduction is associated with water, the Carboniferous is also dominated by amphibians (amphibians), whose reproduction is also associated with water.

At the end of the Carboniferous, amphibians gave rise to reptiles, or reptiles, much better adapted to life on land.

The first flying insects, potential plant pollinators, also appeared in the Carboniferous. The most interesting of them is the giant dragonfly Meganeura with a wingspan of up to 1.5 m.

The largest aromorphoses of the Carboniferous are the appearance of reptiles and flying insects.

The Mesozoic era includes three periods - Triassic, Jurassic and Cretaceous.

Triassic

During the Triassic period, a continental, arid climate prevailed on Earth. Therefore, the dominant position was occupied by gymnosperms and reptiles, which had a number of adaptations for transporting unfavorable conditions, lack of moisture.

The wide distribution of gymnosperms is explained by the fact that in arid climates they had a number of advantages over ferns. An important aromorphosis was the appearance of a coated seed with a reserve nutrients. This provided the embryo with nutrition and protection from unfavorable environmental conditions. The egg developed inside the ovule and was protected from exposure to adverse factors external environment. Thus, the reproduction of these plants did not depend on the availability of water.

Among animals, reptiles are widespread. Their appearance was due to a number of aromorphoses: internal fertilization, dense shells and supply of nutrients in the egg, horny integument of the body, more advanced respiratory and circulatory systems.

During the Triassic period, an important event for the subsequent history of the Earth occurred - the first primitive mammals appeared.

Jurassic period

During the Jurassic period, the climate becomes more humid and warmer, and powerful vegetation develops. Trees reach enormous sizes, such as sequoias. Some types of sequoia have survived to this day. Thus, in California, the Mammoth tree grows, the height of which reaches 100 m, the diameter of the trunk is 12 m, and its life expectancy is over 2500 years.

The rapid development of vegetation during the Jurassic period provided a good food supply, which led to the appearance of giant reptiles. Brontosaurus, for example, reached a length of 20 m, and diplodocus - 26 m. These huge animals fed on lush aquatic vegetation. The large, massive body limited their ability to move on land.

Ichthyosaurs and plesiosaurs lived in reservoirs. Plesiosaurs 1000 reached from 0.5 to 15 m in length, had flippers, a wide flat body and a small head on long neck. They ate fish and small aquatic animals.

During the Jurassic period, flying reptiles appeared: rhamphorhynchus and pterodactyls. The first ones had a long tail and narrow wings, and the second - wide wings and a short tail. These animals lived on the coasts and ate mainly fish.

Cretaceous period

During the Cretaceous period there was sudden change climate as a result of cloud dispersal and increased solar radiation. As a result, the number of ferns and gymnosperms decreased, and the first angiosperms appeared.

Ancient reptiles were the ancestors of birds and mammals, as evidenced by paleontological finds. Thus, prints of animals were discovered that combined the characteristics of birds and reptiles. They had wings, and their body, like birds, was covered with feathers. However, like reptiles, they had a long tail of 20-21 vertebrae, scales were preserved on the head, fingers were on the limbs, teeth were placed on the jaws, and the trunk vertebrae were movably connected. These animals lived in trees and ate insects or fruits.
For a long time The direct ancestors of birds were considered to be Archeopteryx, a skeletal imprint of which was found in the sediments Jurassic period. However, later paleontological finds showed that true birds appeared at the same time as Archeopteryx. (According to some scientists, Archeopteryx is a feathered reptile, a dead-end branch in the evolution of reptiles.)

The evolution and spread of birds was determined by the following aromorphoses: the appearance of a four-chambered heart and warm-bloodedness, feathers, a more developed nervous system (an increase in the size of the cerebral hemispheres and the appearance of the cerebral cortex), an increase in nutrient reserves in the egg and the formation of a calcareous shell.

Thanks to aromorphoses, the dependence of birds on environment. Despite changes in ambient temperature, they maintain a constant body temperature, so they are active even in winter and do not fall into torpor, like reptiles. The supply of nutrients in the egg and the presence of a calcareous shell provided nutrition and protection for the embryo. The development of the brain has complicated the behavior of birds: they have well-developed care for their offspring and have developed complex conditioned reflexes, which ensures the prosperity of this group of animals.
The ancient toothed reptiles are considered the ancestors of mammals. From these animals a group of small reptiles separated, which had a constant body temperature and gave birth to live young. From them came the first mammals, reminiscent of rats and hedgehogs.

Among the aromorphoses that caused the appearance of mammals, it should be noted the appearance of a four-chambered heart, hairline, thanks to which thermoregulation was improved, warm-bloodedness arose, and the nervous system developed, especially the cerebral hemispheres and the cerebral cortex; viviparity and feeding of young with milk. These changes ensured the survival and resettlement, offspring, and dominance of mammals on Earth.

At the end Mesozoic era During the Cretaceous period, there was a mass extinction of animals. According to scientists, at the end Cretaceous period 17% of families and 45% of genera of living organisms became extinct, including dinosaurs. There are many hypotheses about the reasons for the extinction of dinosaurs, some of them are evolutionary, others are catastrophic.

Evolutionary hypotheses explain the extinction of dinosaurs by gradually acting causes - climate change, plant communities. According to this hypothesis, a change in climate to hot and dry conditions contributed to the mass extinction of plants. Reducing quantity plant food led to the extinction of herbivores and then carnivores.

In accordance with the catastrophe hypothesis, the Earth collided with a small asteroid or a large d16 meteorite, which resulted in an increase in dust in the atmosphere. Dust hampered the process of photosynthesis, plants began to die out, and then animals.

Evolution of animals. Battle for Life - Size.

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Paleozoic era in Cambrian period was represented by organisms that live mainly in aquatic environment. Widespread large sizes multicellular brown and green algae.

The transition of plants to life on land

In the Silurian, and possibly even in the Ordovician or Cambrian period, in some populations of green algae that lived in temporarily dry reservoirs, as a result of aromorphosis, tissues were formed that first appeared in land plants - psilophytes.

Psilophytes- collective name. They were small in size, no higher than half a meter, with a stem-like above-ground part and a rhizome from which rhizoids emerged. Some of them still closely resembled algae, while others already bore characteristics that brought them closer to bryophytes and fern-like plants.

The growth of plants on land was possible because a small layer of soil was already formed by the activity of bacteria, blue-green algae and protozoa. By this time, mushrooms also appeared, which also contributed to soil formation with their vital activity.

Marine fauna

The seas of the Cambrian, Ordovician, and Silurian periods were inhabited by protozoa, sponges, coelenterates, arthropods, mollusks, echinoderms, and lower chordates. During the Silurian period, the most primitive vertebrates appeared - cyclostomes. They do not yet have jaws, but thanks to aromorphosis, a skull and vertebrae appear. During the Devonian period, there was a flourishing of the scutes from the class of cyclostomes.

In the evolution of vertebrates there is again a significant increase in organization. A jaw apparatus appeared in the skull, giving them the opportunity to actively hunt and capture prey. This contributed to the process natural selection increasing the organization of the nervous system, sensory organs, improving instincts. Of the modern fauna, the closest to these are the oldest fish- sharks and rays.

Lobe-finned fish also appeared. A few of their representatives have now been found in Indian Ocean, off the coast of Africa. Lobe-finned fish, which lived in drying up reservoirs, took an important step in the evolution of animals during the Devonian period - reaching land.

The first terrestrial vertebrates were the most ancient amphibians, stegocephalians - descendants of lobe-finned fish. The skeleton of the fins of lobe-fins is homologous to the skeleton of the five-fingered limb. In stegocephalians, like modern amphibians, eggs and larvae could only develop in water, so they were forced to live only near bodies of water.

Increased organization of land plants

During the Devonian period, plants experienced an important aromorphosis: a special apparatus for absorbing mineral solutions (root) developed; The leaf is formed as the main organ of carbon dioxide assimilation. Thus, differentiation into stem, leaves and root appeared. The first leafy plants were mosses. Their relationship with algae and psilophytes is revealed in the fact that their protonema is similar to green algae, instead of roots there are rhizoids, fertilization occurs in the aquatic environment. In the Devonian period, higher spores evolved from psilophytes: mosses, horsetails, and ferns. They have well-formed roots, but to reproduce they need water in which the reproductive cells move.

Fern blossoming

IN flora Another aromorphosis occurred - the appearance of seed ferns. The seed is equipped with an outer skin that protects it from unfavorable conditions, and nutritious material accumulates inside. Seed plants do not need water for fertilization, which ensured their conquest of land.

The climate of the ensuing Carboniferous period was warm and humid. The atmosphere contained a large percentage of carbon dioxide. This contributed to the lush development of ferns and, as a consequence, their heyday. Some horsetails reached a height of 30 meters.

The role of plants in the access of animals to land

The development of terrestrial vegetation favored the formation of soils. From the remains of vegetation of that period, coal was formed. A significant portion of atmospheric carbon appeared to be preserved in it. As a result of intensive photosynthesis carried out by green plants, the atmosphere was enriched with oxygen. Change chemical composition The atmosphere was prepared for the possibility of animals populating the land.

First land animals

The climate of the Carboniferous period also contributed to the flourishing of amphibians (stegocephalians). They did not yet have enemies on land, and numerous worms and arthropods, especially arachnids and insects that inhabited the land, served rich food. As a result of divergence and idioadaptations, numerous species of stegocephalians existed. Some of them reached gigantic sizes (up to 47 m in length).

Climate change

At the end of the Carboniferous, and especially during the Permian period, the climate changed and became dry. This led to the extinction of ferns and amphibians. Surviving species were formed only from a few populations of both. Most of the surviving fern-like plants and amphibians are represented by small species that live in damp places. Not only amphibians, but also reptiles evolved from stegocephalians.

Adaptation to new conditions

The origin of reptiles is associated with aromorphoses that ensure reproduction on land: internal fertilization, a supply of nutrients in the egg, covered with a dense shell that protects it from the drying effects of air. Liquid accumulates inside the shells of the developing egg, in which, like in an aquarium, the development of the embryo occurs. This allowed the reptiles to conquer all habitats: land, air, and move again into water.

The progress of reptiles was facilitated by the development of horny cover, which protects from drying out, more advanced development of the lungs, circulatory system, limbs, brain. All this gives reason to recognize reptiles as the first true terrestrial vertebrates.

Palaeozoic. The work was completed by students of grade 9 “G” Bondar Anastasia and Ivanova Maria, Pikalevo, 2011 Contents. 1. 2. 3. 4. 5. 6. Beginning and continuation. Climate. Representatives. Vegetable world. Animal organisms The most important aromorphoses. Period Beginning End Early Paleozoic Cambrian 542 Ma 488 Ma Ordovician 488 Ma 443 Ma Silurian 443 Ma 416 Ma Late Paleozoic Devonian 416 Ma 359 Ma Carboniferous 359 Ma 299 Ma Permian 299 Ma 251 Ma Climate Paleozoic The climate of the early Paleozoic was quite monotonous: most of the land surface was occupied by areas with an arid climate. Only near the equator were there areas with a tropical humid climate. Starting from the Silurian period of the Paleozoic era, the climate becomes cooler. In the Middle Devonian, areas with a tropical humid climate occupied almost all areas near the equator and on the coasts of tropical seas. In the late Paleozoic, the climate became more severe. The cooling was facilitated by the concentration of most of the southern continents into a single supercontinent, Gondwana, which rose high above the surrounding seas. Vegetable world. During the Paleozoic, some groups of plants were gradually replaced by others. At the beginning of the era, from the Cambrian to the Silurian, seaweed dominated, but already in the Silurian, higher vascular plants growing on land appeared. Until the end of the Carboniferous period, spore plants predominated, but in, especially in its second half, a significant part of terrestrial vegetation consists of seed plants from the group of gymnosperms (Gymnospermae). Before the beginning of the Paleozoic, with the exception of a few questionable finds of spores, there are no signs of the development of land plants. However, it is likely that some plants (lichens, fungi) began to penetrate into the interior of the land in the Proterozoic, since sediments from this time often contain significant amounts of nutrients necessary for plants. In order to adapt to new living conditions on land, many plants had to radically change their anatomical structure. Animal organisms. It was in the Paleozoic that living organisms came to land and the “skeletal revolution” occurred, when many organisms acquired shells, shells and skeletons. The Paleozoic world is dominated by arthropods: spiders, scorpions, giant dragonflies, cockroaches, beetles. Fish lived in the water, on the basis of which amphibians and insectivorous small reptiles appeared in the Devonian. Giant ferns and horsetails stood out from the vegetation, which formed dense thickets . During the Carboniferous period, the earth appeared- cordaite taiga, with trees reaching a height of 20 meters. The most important group of animals of the early Paleozoic are trilobites, which flourished in the Cambrian and Ordovician. In the Silurian they were replaced by cephalopods. The most important aromorphoses. A continental, arid climate prevailed on Earth. Therefore, the dominant position was occupied by gymnosperms and reptiles, which had a number of adaptations to endure unfavorable conditions and lack of moisture. The wide distribution of gymnosperms is explained by the fact that in arid climates they had a number of advantages over ferns. An important aromorphosis was the appearance of a coated seed with a supply of nutrients. This provided the embryo with nutrition and protection from unfavorable environmental conditions. The egg developed inside the ovule and was protected from the effects of unfavorable environmental factors. Thus, the reproduction of these plants did not depend on the availability of water. Gymnosperms had well-developed integumentary and conductive tissues, and the leaves were modified into needles, which, on the one hand, improved the supply of water to the plants, and on the other, reduced its evaporation. Among animals, reptiles are widespread. Their appearance was due to a number of aromorphoses: internal fertilization, dense membranes and a supply of nutrients in the horny integument of the body, more advanced respiratory and circulatory systems. During this period, an important event occurred - the first primitive mammals appeared.

The Paleozoic era consists of six periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous (Carboniferous), Permian.

Cambrian. The name comes from the area where geological layers with the remains of organisms were first discovered. The Cambrian climate was warm, there was no soil on land, so life developed in an aquatic environment. On land, only bacteria and blue-green algae were found. Green diatoms and golden algae swam freely in the seas, and red, brown algae were attached to the bottom. In the initial Cambrian period, salts washed off the land increased the salinity of the seas, especially the concentration of calcium and magnesium. Marine animals freely absorbed mineral salts on their body surfaces. Trilobites appeared - ancient representatives of arthropods, similar in body shape to modern woodlice. The mineral salts that were absorbed into their body formed a chitinous shell on the outside. Trilobites with a chitin-shell body, divided into 40-50 sections, swam freely at the very bottom of the sea (Fig. 39).

Rice. 39. Early Paleozoic fauna (Cambrian, Ordovician, Silurian): 1 - archaeocyte colony; 2 -- skeleton of Silurian coral; 3 - jellyfish; 4 - Silurian shells cephalopods; 5 - brachiopods; 6 - trilobites - the most primitive crustaceans (Cambrian)

In the Cambrian period appeared different kinds sponges, corals, mollusks, sea ​​lily, later sea urchin. This period is also called the period of invertebrate development.

Ordovician(the name is given by the name of the tribe that once lived at the site where the fossil remains were discovered). Brown and red algae and trilobites continued to develop in the sea. The ancestors of modern octopuses and squids appeared - cephalopod snails (molluscs), as well as brachiopods, gastropods. The ancestors of modern lampreys were found in geological strata, hagfish - the skeleton of jawless vertebrates. Their body and tail were covered with dense scales.

Silur(by tribe name). Due to the beginning of active mountain-building processes, the distribution of sea and land changed, the size of the land increased, and the first vertebrates appeared. Huge people lived in the seas Cancerscorpios-predatory arthropods that reached 2 m in length and had 6 pairs of limbs. The front pair of those located around oral cavity limbs were turned into claws for grinding food. In the Silurian period, the first vertebrates appeared - armored fish (Fig. 40).

Rice. 40. Jawless armored "fish"

Their internal skeleton was cartilaginous, and on the outside the body was enclosed in a bony shell consisting of scutes. Due to the lack of paired fins, they crawled along the bottom rather than swam. They resembled fish in body shape, but actually belonged to the class jawless(cyclostomes). The clumsy shellfish did not develop and died out. Modern cyclostomes lampreys And hagfish- close relatives of armored fish.

At the end of the Silurian, intensive development of land plants began, prepared by the earlier emergence of bacteria and blue-green algae from the water. soil formation. Plants were the first to colonize land - peilophytes(Fig. 41).

Rice. 41. The first plants to reach land were psilophytes and rhinophytes.

Their structure was similar to that of multicellular green algae; there were no real leaves. With the help of thin thread-like processes, they strengthened themselves in the ground and absorbed water and mineral salts. Along with psilophytes, arachnids came onto land, reminiscent of modern scorpions. At the end of the Silurian, shark-like creatures also lived predatory fish with a cartilaginous skeleton. The appearance of jaws played a major role in the development of vertebrates. The settlement of land with plants and animals began.

Devonian(named after the county of Devonshire in Southern England) is called the period of fish. The size of the seas decreased, deserts increased, and the climate became dry. Cartilaginous animals appeared in the seas (descendants - modern sharks, rays, chimeras) and bony fish. Depending on the structure of the fins, bony fishes were divided into ray-finned (fins similar to a fan) and lobe-finned (fins similar to a brush). Lobe-finned fish had fleshy and short fins. With the help of two pectoral and two pelvic fins, they moved to those lakes where there was still enough water left. With the onset of drought, they adapted to breathing. These fish breathed using a swim bladder equipped with blood vessels. Over time, the paired fins turned into five-fingered limbs, and the swim bladder became lungs. Until recently, it was believed that lobe-finned fishes became extinct at the end of the Paleozoic. However, in 1938 the museum South Africa a fish 1.5 m long and weighing 50 kg was handed over. The fish was named coelacanth in honor of a museum employee, Mrs. K. Latimer. Scientists believe that coelacanth appeared 300 million years ago. The structure of the coelacanth retains the characteristics of amphibians and other vertebrates, including humans (five-fingered limbs). At the end of the Devonian, the first amphibians appeared from lobe-finned fish - stegocephali(Fig. 42).

Rice. 42. Fauna of the second half of the Paleozoic (Devonian, Carboniferous, Permian): 1 - lobe-finned fish (Devonian); 2 - the oldest amphibian - stegocephalus (Carboniferous); 3 - dragonfly (carbon); 4 - the oldest reptile - a predatory lizard - foreigner (Perm); 5 - omnivorous lizard - Dimetrodon (Permian); 6 - herbivorous lizard - pareiasaurus (Permian); 7 - fish-eating lizard (Permian)

In the Devonian period, plants formed spore horsetails, mosses, ferns. Seed ferns were widespread. Land plants enriched the air with oxygen and provided animals with food.

Carbon(Carboniferous period) (named due to the thick deposits of coal during this period). The climate during this period became humid, warm, and the swamps again encroached on land. Giant tree mosses - lepidodendron and sigillaria, calamnites- 30-40 m high, 1-2 m wide formed dense forests. Vegetation began to develop especially rapidly in the middle of the Carboniferous period (Fig. 43).

Rice. 43. Tree-like plants of the Carboniferous period

Seed ferns gave rise to gymnosperms, and in the evolution of plants the seed method of reproduction appeared. Stegocephals, which appeared in the Upper Devonian, reached great development. The body shape of stegocephalus resembled a newt and a salamander; they reproduced by throwing eggs. Thanks to the development of larvae in water and respiration using gills, the development of amphibians is still associated with water. Between amphibians and reptiles there is a period of 50 million years. The environment has always influenced the evolution of organisms.

Permian(by city name). There was a rise in mountains, a decrease in land size and climate change. At the equator the climate became humid and tropical, while to the north it became warm and dry. Ferns, horsetails, and mosses, adapted to humid climate. For changing spore plants gymnosperms arrived.

Significant changes have also occurred in the animal world. The dry climate contributed to the disappearance of trilobites, Paleozoic corals, and amphibians - stegocephalians. But the oldest reptiles have achieved significant diversity. They laid eggs that had a special layer of liquid that protected the embryo from drying out. In addition, the complication of the lungs created the prerequisites for protecting the body of reptiles with scales, which protected the body from drying out and prevented skin respiration. Thanks to such characteristics, reptiles have spread widely on Earth.

Among reptiles, intermediate forms between amphibians began to develop - cotylosaurs, 25 cm long. Their body was similar to lizards, and their head was like a frog; they ate fish. Fossil remains of beast-toothed lizards, from which mammals originated, have been found).

Permian aromorphosis.

1. Reproduction by laying eggs (the liquid inside the egg protects the embryo from drying out), internal (female body) fertilization of the egg has appeared.

2.Keratization of the body (protects from drying out).

1. Mobility of the cervical vertebra, free rotation of the head and quick response to environmental actions.

2. Development of muscles, respiratory organs, blood circulation, appearance of the rudiments of the brain.

3. Free support of the body on the limbs (necessary for rapid movement).

Paleozoic. Cambrian. Ordovician. Silur. Devonian. Carboniferous (Carboniferous period). Permian. Psilophytes. Stegocephals. Gymnosperms.

1.Periods of the Paleozoic era.

2.Aromorphoses of the Paleozoic.

1.Give a description of each period of the Paleozoic.

2.Give examples of plant and animal species that appeared in the Silurian and Devonian.

1.Prove the advantage of the Paleozoic compared to the Archean and Proterozoic.

2.Name the first species of plants and animals that came onto land. What period do they belong to?

1.Make a comparative development diagram organic world in the Carboniferous and Devonian periods.

2.Name the aromorphoses of the Permian period.