Question 1. When did the first land plants appear? What were they called and what distinctive features had?
At the beginning of the Paleozoic era (era ancient life) plants inhabit mainly the seas, but after 150–170 million years the first terrestrial plants appear - psilophytes, occupying an intermediate position between algae and terrestrial vascular plants. Psilophytes already had poorly differentiated tissues capable of carrying water and organic matter, and could establish themselves in the soil, although they still lacked real roots (as well as real shoots). Such plants could only exist in a humid climate; when arid conditions were established, the psilophytes disappeared. However, they gave rise to more adapted land plants.
Question 2. In what direction did the evolution of plants on land go?
The further evolution of plants on land went in the direction of dividing the body into vegetative organs and tissues and improving the vascular system (ensuring the rapid movement of water to high altitudes). Spore-bearing plants (horsetails, mosses, ferns) are widespread.
Question 3. What evolutionary advantages does the transition of plants to seed reproduction provide?
The transition to seed propagation gave plants many advantages: the embryo in the seed is now protected from unfavorable conditions shells and provided with food. In some gymnosperms (conifers), the process of sexual reproduction is no longer associated with water. Pollination in gymnosperms is carried out by the wind, and the seeds are equipped with devices for distribution by animals. All this contributed to the spread of seed plants.
Question 4. Describe animal world Paleozoic
The fauna in the Paleozoic era developed extremely rapidly and was represented by a large number of diverse forms. Life in the seas flourished. At the very beginning of this era (570 million years ago), all the main types of animals, except chordates, already existed. Sponges, corals, echinoderms, mollusks, huge predatory crustaceans - this is an incomplete list of the inhabitants of the seas of that time.
Question 5. Name the main aromorphoses in the evolution of vertebrates in the Paleozoic.
A number of aromorphoses can be traced in vertebrates of the Paleozoic era. Of these, the appearance of jaws in armored fish, the pulmonary method of respiration and the structure of fins in lobe-finned fish are noted. Later, major aromorphoses in the development of vertebrates were the appearance of internal fertilization and the formation of a number of egg shells that protect the embryo from drying out, complication in the structure of the heart and lungs, and keratinization skin. These profound changes led to the emergence of the class of reptiles.
Question 6. What environmental conditions and structural features of vertebrates served as prerequisites for their emergence onto land?
Most of the land was a lifeless desert. Along the shores of freshwater reservoirs, annelids and arthropods lived in dense thickets of plants. The climate is dry, with sharp temperature fluctuations throughout the day and between seasons. The water level in rivers and reservoirs changed frequently. Many reservoirs dried up completely and froze in winter. When water bodies dried out, aquatic vegetation died and plant residues accumulated. Their decomposition consumed oxygen dissolved in water. All this created a very unfavorable environment for fish. In these conditions, only breathing could save them atmospheric air.
Question 7. Why did amphibians of the Carboniferous period achieve biological prosperity?
Reptiles (creeping things) acquired some properties that allowed them to finally break their connection with the aquatic habitat. Internal fertilization and accumulation of yolk in the egg made possible reproduction and development of the embryo on land. The keratinization of the skin and the more complex structure of the kidney contributed to a sharp decrease in water loss by the body and, as a consequence, to widespread dispersal. The appearance of the chest provided a more efficient type of breathing than in amphibians - suction. The lack of competition caused the widespread spread of reptiles on land and the return of some of them - ichthyosaurs - to the aquatic environment.
Question 8. Summarize the information obtained from this paragraph into a single table “The evolution of flora and fauna in the Paleozoic era.”
Question 9. Give examples of the relationship between the evolutionary transformations of plants and animals in the Paleozoic.
In the Paleozoic, the organs of reproduction and cross-fertilization in angiosperms were improved in parallel with the evolution of insects;
Question 10. Is it possible to say that aromorphoses are based on idioadaptations - particular adaptations to specific environmental conditions? Give examples.
Aromorphoses are indeed based on particular adaptations to specific environmental conditions. An example of this is the emergence of gymnosperms due to climate change - it has become warmer and wetter. In animals, such an example is the appearance of paired limbs as a consequence of deteriorating environmental conditions and subsequent access to land.
Looking at my home cactus, I couldn’t help but think: “How did plants even begin their journey on land? And when did this happen?” About this very interesting topic I would like to tell you.
How and when did the first sushi plants appear?
As is known, all earthly life originated in water. And plants are no exception. Once upon a time they were all protozoan algae, but then a stage came when they began to germinate on land.
And they began their emergence to the surface at the end Silura (near 4 05-440 million years ago), what in Paleozoic era. Then powerful events were actively taking place mining processes, leading to shallowing and drying up of many seas. This is what caused some algae to “come out” onto land.
The very first plants on the surface are psilophytes. They had only a bare stem, which was attached to the ground with the help of special outgrowths - rhizoids. The psilophytes themselves had a very simple structure, but they had branching stems with outgrowths that stored disputes.
Psilophytes preferred marshy and wet area, because they did not have a powerful root system to extract water. Today it is believed that such plants once lined endless carpets on the bare surface of the Earth.
In addition, psilophytes could be like very high(much larger than human height), and very low and tiny.
How did the first land plants adapt?
Worth a special mention fixture system, which plants have mastered for life on land. After all, they are very different from life under water. So, these difficulties could be called:
- necessity water conservation from its evaporation in air;
- need for education hard protective cover;
- adaptation to constantly changing conditions environment.
And many others. Such plants also needed to learn to carry out more complex photosynthesis, anchor in the soil and get from it the necessary minerals .
All these difficulties were overcome by plant organisms. And the evidence of this is our life on Earth.
Our planet has not always been green. A long time ago, when life was just beginning, the land was empty and lifeless - the first forms chose the World Ocean as their habitat. But gradually the earth's surface also began to be developed by various creatures. The first plants on Earth are also the earliest land inhabitants. What were the ancestors of modern representatives of the flora?
Photo: pikabu.ruSo imagine the Earth 420 million years ago, in an era called the Silurian period. This date was not chosen by chance - it was at this time, scientists believe, that plants finally began to conquer the land.
For the first time, the remains of Cooksonia were discovered in Scotland (the first representative of the terrestrial flora was named after Isabella Cookson, a famous paleobotanist). But scientists suggest that it was distributed throughout the globe.
It was not so easy to leave the waters of the World Ocean and begin to develop land. To do this, plants had to literally rebuild their entire organism: acquire a shell resembling a cuticle, protecting it from drying out, and acquire special stomata, with the help of which it was possible to regulate evaporation and absorb substances necessary for life.
Cooksonia, which consists of thin green stems not exceeding five centimeters in height, was considered one of the most developed plants. But the Earth’s atmosphere and its inhabitants were rapidly changing, and the oldest representative of the flora was increasingly losing its position. At the moment, the plant is considered extinct.
Photo: stihi.ru The remains of the nematothallus do not even remotely resemble plants - they look more like shapeless black spots. But despite its strange appearance, in development this plant has gone far ahead of its comrades in its habitat. The fact is that the cuticle of the nematothallus is already more similar to what we have today existing plants parts - it consisted of formations reminiscent of modern cells, which is why it received the name pseudocellular. It is worth noting that in other species this shell simply looked like a continuous film.
Nematothallus has given a lot of food for thought to the scientific world. Some scientists attributed it to red algae, others were inclined to think that it was a lichen. And the mystery of this ancient organism has not yet been solved.
Photo: amgpgu.ru Rhinia and almost all other ancient plants with a vascular structure are classified as rhiniophytes. Representatives of this group have not grown on Earth for a long time. However, this fact does not at all prevent scientists from studying these living creatures that once dominated the land - many fossils found in many parts of the planet allow us to judge both the appearance and the structure of such plants.
Rhiniophytes have several important features, which allow us to assert: these living beings are completely different from their descendants. Firstly, their stem was not covered with soft bark: scale-like processes grew on it. Secondly, rhinophytes reproduced exclusively with the help of spores, which were formed in special organs called sporangia.
But the most important difference is that these plants did not have any root system. Instead, there were root formations covered with “hairs” - rhizoids, with the help of which rhinia absorbed water and substances necessary for life.
Photo: bio.1september.ru This plant was recently considered a representative of the animal world. The fact is that its remains - small, round in shape - were initially mistaken for the eggs of frogs or fish, algae, or even the eggs of long-extinct crustacean scorpions. The parks discovered in 1891 put an end to the misconceptions.
The plant lived on our planet about 400 million years ago. This time dates back to the beginning of the Devonian period.
Photo: bio.1september.ru The remains of pachyteca, like the parka fossils found, are balls small size(the largest discovered has a diameter of 7 millimeters). Quite little is known about this plant: scientists were only able to establish the fact that it consisted of tubes arranged radially and converging in the center, where the core was located.
This plant is a dead-end branch of flora development, in fact, like parkas and rhineries. It has not been possible to establish for certain what was the impetus for their emergence and why they became extinct. The only reason, according to scientists, is the development of vascular plants, which simply displaced their less developed relatives.
Plants that made it onto land chose a completely different path of development. It was thanks to them that the animal world arose and, accordingly, an intelligent form of life appeared - man. And who knows what our planet would look like now if the Rinias, Parks and Cooksonias had not decided to develop land?..
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400 million years ago, a huge part of the earth's surface of our planet was occupied by seas and oceans. The first living organisms arose in aquatic environment. They were particles of mucus. After several million years, these primitive microorganisms developed a green color. By appearance they began to look like algae.
Climatic conditions favorably affected the growth and reproduction of algae.
Over time, the surface of the earth and the bottom of the oceans have undergone changes. New continents arose, while old ones disappeared under water. Earth's crust was actively changing. These processes led to the appearance of water on the earth's surface.
Retreating sea water fell into crevices and depressions. They then dried up, then filled with water again. As a result, those algae that were on the seabed gradually moved to earth's surface. But since the drying process occurred very slowly, during this time they adapted to the new living conditions on earth. This process took place over a million years.
The climate at that time was very humid and warm. It facilitated the transition of plants from marine to terrestrial life. Evolution led to a more complex structure various plants, ancient algae also changed. They gave rise to the development of new earthly plants - psilophytes. In appearance, they resembled small plants that were located near the banks of lakes and rivers. They had a stem that was covered with small bristles. But, like algae, psilophytes did not have a root system.
Plants in a new climate
Ferns evolved from psilophytes. The psilophytes themselves ceased to exist 300 million years ago.
Humid climate and a large number of waters led to rapid spread different plants– ferns, horsetails, mosses. The end of the Carboniferous period was marked by a change in climate: it became drier and colder. Huge ferns began to die out. The remains of dead plants rotted and turned into coal, which people then used to heat their homes.
Ferns had seeds on their leaves, which were called gymnosperms. From giant ferns came modern pines, spruces, and firs, which are called gymnosperms.
With climate change, ancient ferns have disappeared.
The cold climate destroyed their tender sprouts. They were replaced by seed ferns, which are called the first gymnosperms. These plants have adapted perfectly to the new conditions of a dry and cold climate. In this plant species, the reproduction process did not depend on water in the external environment.
130 million years ago, various shrubs and herbs arose on Earth, the seeds of which were located in the surface of the fruit. They were called angiosperms. Angiosperms have lived on our planet for 60 million years. These plants have remained virtually unchanged from then to the present day.
Without plants, our planet would be a lifeless desert. And tree leaves are small factories or chemical laboratories, where substances are transformed under the influence of sunlight and heat. Trees not only improve the composition of the air and soften its temperature. Forests have medicinal value and provide most of our food needs, as well as materials such as wood and cotton; They are also raw materials for the production of medicines.
I. What were the very first plants on earth?
Life on Earth began in the sea. And plants were the first to appear on our planet. Many of them made it to land and became completely different. But those that remained at sea remained almost unchanged. They are the most ancient, it all began with them. Without plants, life on Earth would not be possible. Only plants can absorb carbon dioxide and release oxygen. For this they use Sun rays. One of the first plants on earth were algae.
More than 20,000 species of algae are known. They can be anchored to rocks or the seabed using a foot-like “brace” that extends into a branch with leaves. Brown algae grows in cold waters and reaches enormous sizes. Red algae are characteristic of warm seas. Green and blue-green algae can be found in both warm and cold waters. Brown algae produces a lot of useful substances, used in the production of plastics, varnishes, paints, paper and even explosives. They are used to make medicine, fertilizer, and feed for livestock. Among the peoples South-East Asia seaweed is the basis of many dishes.
Algae "Floating Forest".
In the old days there were legends about the Sargasso Sea, where ships died after getting stuck in algae. But still, in some places the algae thickets are so thick that they can hold up a light boat. This is the brown algae called sargassum, after which the sea itself is named. Sargassum looks like bushes dotted with “berries” - air bubbles allowing the plant to float on the surface of the water. Unlike other large algae, sargassum does not attach to the bottom and travels along the waves in huge clusters, forming a floating forest. A myriad of mollusks, worms, and bryozoans attach to the leaves of Sargassum; crabs, shrimp, and fish hide in its thickets. Almost all of the “residents” are brownish-yellow in color, similar to sargassum, and their bodies often copy the shapes of the “leaves” of this algae. Some hide so as not to scare off their prey. So this whole community floats, never touching the shore.
II. They feed, clothe, make you happy.
1. Trees that provide food.
Coffee is one of the most popular drinks in the world.
Who gave us this wonderful drink and how? If you believe the ancient Arab legend, then we owe the discovery of coffee. goats. One Ethiopian shepherd, according to legend, noticed that his goats, having eaten some berries from a bush, continued to graze all night, without thinking of resting. The shepherd told about this wise old man, and he, having tasted these berries, opened them miraculous power and invented the drink coffee.
The Ethiopians liked coffee so much that later one of the tribes, having moved to the Arabian Peninsula, took its grains with them. This was the beginning of the first coffee plantations. And this happened, as is known from ancient manuscripts, in the 9th century. Coffee was known only to the Arabs for quite a long time, but the Turks, who conquered it in the 15th-16th centuries. Part Arab territories, also appreciated the taste and wonderful properties drink This is how the famous method of making Turkish coffee appeared: coffee is brewed on hot sand in special copper vessels with a handle - “Turks”.
Europeans were first introduced to coffee by an Italian who returned from Turkey. A doctor by profession, he recommended his patients to drink coffee for medicinal purposes. Venice was the first to import coffee to Europe. And in 1652 the first coffee shop was opened in England. Turkey was the monopoly supplier of coffee to Europe, but the cunning Dutch, having stolen seedlings of coffee trees from the Turks, transported them to Indonesia, where the climate was quite suitable for growing coffee.
Brazil is now the world leader in coffee production.
Coffee came to Russia thanks to Peter I.
Coffee drink is brewed from processed seeds coffee tree. This evergreen from the madder family. The white lush inflorescences of the coffee tree, located in the axils of the leaves, after pollination by insects turn into fruits - the red berries are removed from them, the seeds are polished in special drums and packed in bags. Before brewing, the coffee beans are roasted.
The birthplace of coffee is Africa. The Arabian variety is considered the highest quality and tastiest. Brazilian coffee (this is not a type, but only a place where coffee is grown), which fills all markets in the world, is much worse in quality than coffee grown in other countries.
2. Noble friends.
Cedrus are real cedars. Phenicia, Egypt, Assyria were powerful powers of antiquity. But they occupied deserted territories; there were almost no forests there. And wood is needed both for the construction of housing and for ships. The wood is strong and rot-resistant. The cedar that the ancients loved is not the cedar that grows in the taiga and is famous for its delicious nuts. Siberian pines are the namesakes of real cedars - cedrus trees.
The Phoenicians cut Cedrus for ships, the Egyptians for sarcophagi for the funeral ceremonies of their nobles, the Greeks and Romans used cedar for building temples and making furniture. Later, the crusaders began cutting down the cedrus trees. And during the First World War, the most valuable cedars with their pink wood, for lack of other fuel, were burned in locomotive furnaces. There are only 4 groves of Lebanese cedars left. True, other types of cedrus - Atlas, Cypriot and Himalayan - although very rare trees, unlike the Lebanese cedar, they are not endangered.
Lebanese cedars are majestic trees with horizontal, powerful branches. Their needles are bluish, collected in tassels. The cones are the size of a fist, dense, almost smooth, like barrels. When the seeds in them ripen, the cones do not open, but crumble, and the ground is covered with a layer of scales. The wind blows the winged seeds off them and spreads them around. If the goats, which local residents raise in abundance, do not eat the young shoots, they may grow into a new generation of beautiful cedars. The fame of the beauty of Lebanese cedars also reached Russia. Therefore, when Russian pioneers saw Siberian pines, tall, majestic, with large cones, they called them cedars.
Siberian cedar is an amazing pine. The main wealth of cedar is its nuts. They contain fats, proteins, starch, vitamins B and D, and the needles contain many healing substances. Nuts contain more than 60% oil, which is superior in many qualities to animal fats and is not inferior in nutritional value to meat and eggs. Under Ivan the Terrible, these nuts were exported abroad, and under Peter I, they began to be used in Russia to prepare a healing and strengthening remedy - nut milk.
Play a huge role pine nuts in the life of animals. “Where there is no cedar,” the hunters say, “there is no sable.” The nuts are eaten by bears and chipmunks, squirrels and various birds.
Cedar resin is also healing. During the Great Patriotic War Cedar balsam helped with wounds and burns. Resin is a necessary raw material for obtaining such a valuable medicine as camphor. Resin is also needed in optical technology.
Cedar wood is also valuable - pencil sticks are made from it, musical instruments, make furniture. Turpentine and other useful products are obtained from sawdust.
III. Study of tree bark.
Norway maple
The maple tree I was watching is young. It has a tree trunk, which thickens every year, and side branches extend from it to form a crown, which consists of smaller branches and leaves. The tree is held in the soil by its roots, which absorb moisture and dissolved minerals. Therefore, the tree trunk is wider at the bottom.
If you smell the bark, the smell is bitter and astringent. In spring, the smell of the bark intensifies and becomes sweetish.
There is no hollow in my tree. But I have met trees with hollows. Various birds make their homes in the hollow.
There are no lichens, mosses or mushrooms on the maple tree that I am observing. Sometimes mushrooms form fungal roots on the roots, supplying the trees with nitrogen and minerals.
On the bark of my tree there are traces left by man: peeled bark and scratches from a knife, which over time it could heal.
IV. Why is my friend the best?
Norway maple – branch with fruits
Maple is one of the most elegant trees growing in our forests. In the spring, when the tree branches are not yet covered with leaves, the maple blooms. Its yellow-green flowers, collected in an inflorescence, are pleasing to the eye. The maple tree is no less elegant in the summer, when its crown becomes “curly.” The autumn outfit is not inferior in beauty to any other plant. The tree seems to be on fire, striking in its richness of shades of crimson and green, orange and yellow. Each leaf has its own color, and each leaf is beautiful in its own way. And they all have the same shape: round with 5-7 sharp protrusions, hence the name Norway maple. Maple is a good honey plant. Up to 10 kg of honey is obtained from one tree. Norway maple sap is very tasty. In Russia, kvass and various soft drinks were prepared from it.
The Canadian flag features a leaf from the Sugar Maple tree. Its sweet juice was used to make maple syrups, molasses, and even maple beer, which was very popular in the 19th century. Canada was the leader in the production of juice products. The maple leaf has become national symbol of this country.
Musical instruments were made from maple wood, which was durable and light. Sport equipment also made from maple. Pharmacists and chemists use the leaves and bark. Maple has another interesting property: it can predict the weather. From the petioles of the leaves, right next to the branch, sometimes “tears” flow drop by drop - the maple seems to be crying. This is the property of maple to get rid of excess moisture. And the “tears” of the maple depend on whether the air is dry or humid. The drier the air, the stronger the evaporation and vice versa. The air becomes humid when rain approaches. If appeared on maple leaves“Tears mean it will rain in a few hours.
V. Fossil trees that remain on earth.
An ancient, ancient ginkgo tree! It appeared on earth back in the time of dinosaurs - 125 million years ago.
years ago. And since then this plant has not changed much. Ginkgo - beautiful tree up to 30 m high, with large fan-shaped leaves. The appearance of ginkgo resembles our common aspen. But it was not there! Ginkgo is a gymnosperm plant, closer to spruce than to flowering plant aspen. In spring, “catkins” appear on the branches along with the foliage. By autumn, large seeds resembling plums hang on the branches. The pulp of the seed, similar to the fruit, is actually just the seed coat. It is edible and tastes salty. The only problem is that it smells like rotten meat. This is a way to attract seed dispersing animals. Ginkgo, although it survived the dinosaurs, did not survive in the wild. This tree became a garden tree. In Japan and China, it is considered sacred and is grown near temples. Now ginkgos are also appearing on the streets of European cities. Ginkgo easily resists atmospheric pollution, diseases, and insects. Ginkgo leaves and wood contain substances that repel insects. Bookmarks made from dried ginkgo leaves will protect ancient manuscripts from bookworms. And walls covered with ginkgo shingles will not allow cockroaches or bedbugs into the house.
CONCLUSION.
What can I do for all the trees?
When I come to the forest, I will not light fires.
This may lead to fires.
I won't destroy birds' nests. Birds eat insects that harm trees. I will not break branches from trees and bushes. I will plant new seedlings in the yard and take care of them in the future.
Acid rain also causes irreparable damage: destruction of crops, flora and fauna, and destruction of buildings.
First land plants
Life originated in water. The first plants, algae, appeared here. However, at some point, land appeared that had to be populated. The pioneers among animals were lobe-finned fish. And among plants?
What did the first plants look like?
Once upon a time, our planet was inhabited by plants that had only a stem. They were attached to the ground by special outgrowths - rhizoids. These were the first plants to reach land.
Scientists call them psilophytes. This is a Latin word. Translated, it means “naked plants.” Psilophytes really looked “naked.” They only had branching stems with ball-shaped outgrowths in which spores were stored. They are very similar to the “alien plants” that are depicted in illustrations for science fiction stories.
Psilophytes became the first land plants, but they lived only in swampy areas, since they did not have roots and could not get water and nutrients in the thickness of the soil. Scientists believe that these plants once created entire huge carpets over the bare surface of the planet. There were both tiny plants and very large ones, taller than human height.
How did scientists learn about the first plants?
Scientists learned that such plants once existed on our planet only at the beginning of the last century, in 1912, thanks to a Scottish village doctor, who was interested in geology. While examining the soil, he discovered the remains of hitherto unknown plants, which were later called rhinia, after the name of the village in which it was first found. It is believed that it was the first land plant, from which other psilophytes descended.
Ancient plants dominated the planet for millions of years, but became extinct long before humans appeared. But they left their “descendants” - they became horsetails, mosses and ferns. Some scientists believe that lower psilophytes became the ancestors of modern mosses.
Question 1. When did the first land plants appear?
At the beginning of the Paleozoic era, plants inhabited mainly the seas, but in the Ordovician - Silurian the first land plants - psilophytes - appeared (Fig. 1).
Rice. 1. The first land plant
These were small plants, occupying an intermediate position between algae and terrestrial vascular plants. Psilophytes already had a conducting (vascular) system, the first poorly differentiated tissues, and could strengthen in the soil, although roots (like other vegetative organs) were still absent. The further evolution of plants on land was aimed at differentiating the body into vegetative organs and tissues and improving the vascular system (ensuring the rapid rise of water to high altitudes).
Question 2. In what direction did the evolution of plants on land go?
After the appearance of psilophytes, the evolution of plants on land went in the direction of dividing the body into vegetative organs and tissues and improving the vascular system (ensuring the rapid movement of water to high altitudes). Already in the arid Devonian, horsetails, mosses, and pteridophytes were widespread. More greater development reaches terrestrial vegetation in the Carboniferous period (Carboniferous), characterized by a humid and warm climate throughout the year. Gymnosperms appear, descended from seed ferns. The transition to seed propagation gave many advantages: the embryo in the seeds is protected from unfavorable conditions by membranes and provided with food, and has a diploid number of chromosomes. In some gymnosperms (conifers), the process of sexual reproduction is no longer associated with water. Pollination in gymnosperms is carried out by the wind, and seeds have adaptations for distribution by animals. These and other advantages contributed to the widespread distribution of seed plants. Large spore plants die out in the Permian period due to the drying climate.
Question 3. Describe the evolution of animals in the Paleozoic era.
The fauna in the Paleozoic era developed extremely rapidly and was represented by a large number of diverse forms. Life in the seas flourishes. In the Cambrian period, all the main types of animals, except chordates, already existed. Sponges, corals, echinoderms, various mollusks, huge predatory crustaceans - this is an incomplete list of the inhabitants of the Cambrian seas.
In the Ordovician, the improvement and specialization of the main types continued. For the first time, remains of animals that had an internal axial skeleton are being discovered - jawless vertebrates, the distant descendants of which are modern lampreys and hagfishes. The mouth of these peculiar organisms was a simple opening leading to the digestive tract. The anterior section of the digestive tube was pierced by gill slits, between which supporting cartilaginous gill arches were located. The jawless animals fed on organisms that lived in the muddy bottom of rivers and lakes and on detritus (organic remains), sucking food into their mouths. In some jawless animals, division of the gill arches arose, which made it possible to change the lumen of the pharynx with the help of the gill muscles and, therefore, to retain mobile prey that had entered the digestive tube.
The appearance of a grasping mouthpart - large aromorphosis - caused a restructuring of the entire organization of vertebrates.
The appearance of paired fins - limbs - is the next major aromorphosis in the evolution of vertebrates.
In the Silurian period, the first air-breathing animals - arthropods - came onto land along with psilophytes. Intensive development of lower vertebrates continued in reservoirs. It is assumed that vertebrates arose in shallow freshwater bodies of water and only then moved to the seas. The Devonian period was marked by the development of land by other arthropods - spiders; at the end of the period, the first terrestrial vertebrates appear - amphibians (stegocephals). In the Carboniferous period, reptiles (cotylosaurs), flying insects and pulmonary molluscs appeared. In the last, Permian period of the Paleozoic era, rapid development and increase in systematic groups of reptiles was observed; animal-toothed reptiles appear - the ancestors of mammals.
Question 4. What structural features of vertebrates served as prerequisites for their emergence onto land?
In the Silurian period, the first air-breathing animals - arthropods - came onto land along with psilophytes. Intensive development of lower vertebrates continued in reservoirs. It is assumed that vertebrates arose in shallow freshwater bodies of water and only then moved to the seas. In the Devonian, vertebrates are represented by three groups: lungfish, ray-finned and lobe-finned fish. It was lobe-finned fish that gave rise to the development of terrestrial vertebrates. Lobe-finned fish were typically aquatic animals, but could breathe atmospheric air using primitive lungs, which were protrusions of the intestinal wall. Only lobe-finned fish were able to adapt to life on land. Their fins were blades consisting of individual bones with muscles attached to them (Fig. 2). With the help of fins, lobe-finned fish - large animals from 1.5 to several meters in length - could crawl along the bottom. Thus, they had two main prerequisites for the transition to a terrestrial habitat: muscular limbs and lungs. At the end of the Devonian, lobe-finned fish gave rise to the first amphibians - stegocephalians.
Rice. 2. Skeleton of the paired fin of lobe-finned fish and stegocephalus:
A - shoulder girdle and fin of lobe-finned fish;
B - internal skeleton of the fin;
B - skeleton of the forelimb of stegocephalus:
1 - element corresponding to the humerus;
2 - element corresponding to the radius;
8 - element corresponding to the ulna;
4, 5, 6 - carpal bones; 7 - phalanges of fingers.