The number of reptile species on earth. Class Reptiles, or Reptiles (Reptilia) General characteristics of the class. General purchase rules

The topic of this article is reptiles. Species, origin, habitats, as well as some other facts about them will be presented in it.

The word "reptile" comes from a Latin term meaning "to crawl", "to crawl". This implies the nature of the movement of representatives of this class. It should be noted, however, that not all reptiles are animals that can only crawl. There are those who are good at jumping, running, swimming, and even practically flying, gliding like flying squirrels.

ancient reptiles

These animals lived long before the appearance of man on our planet. The reptiles living on Earth today are only relics (insignificant remnants) of a class that was very diverse and rich in the past. We are talking about reptiles that reached their peak in (about 230-67 million years BC). Ancient reptiles were represented in a huge number of forms. Some of their species lived on land. One can note among them large predatory tarbosaurs and giant herbivorous brontosaurs. Others, such as ichthyosaurs, lived in the water. Still others could fly like birds. The amazing world of ancient reptiles has not yet been fully explored. Perhaps in the near future, scientists will encounter new discoveries.

In 1988, the remains of reptiles were discovered in Scotland. According to experts, these reptiles lived 340 million years ago. It was, as it turned out, the most ancient species of fossil reptiles known today. Their body was only 20.3 cm long.

Origin of ancient reptiles

Ancient reptiles evolved from ancient amphibians. This event was the next step in the adaptation of vertebrates to life on land. Today, amphibians and reptiles coexist. Amphibians are otherwise called amphibians, and reptiles are called reptiles.

Groups of modern reptiles

Reptiles (modern) include the following groups.

1. crocodiles. These are large animals with a lizard-like body. There are only 23 species of them, which include real crocodiles, as well as alligators, caimans and gharials.

2. beakheads. They are represented by just one species of tuatara called Sphenodon punctatus. These reptiles (a photo of one of them is presented below) resemble in appearance (up to 75 cm) with a massive body, five-fingered limbs and large heads.

3. scaly. This group of reptiles is the most numerous. It includes 7600 species. These include, for example, lizards, the most numerous group of modern reptiles. This includes: monitor lizards, iguanas, scale-footed, skinks, agamas, chameleons. Lizards are a specialized species that leads a mainly arboreal lifestyle. The scaly ones also include snakes - legless reptiles, as well as amphisbaena - creatures with a worm-like body and a short tail that looks like a head end. Amphisbaena are adapted for a burrowing lifestyle. They very rarely appear on the surface. These reptiles spend most of their lives underground or in the nests of termites and ants that amphisbaena feed on. They usually lack limbs. Representatives belonging to the genus Bipes have only front legs. They can move along earthen passages and tail first. Because of this, they are also called doubles. "Amphisbaena" is translated from Greek as "moving in both directions."

4. Another group - turtles. Their bodies are surrounded by shells from below, from the sides and from above. The shell includes the abdominal (plastron) and dorsal (carapace) shields, which are connected by a bone jumper or tendon ligament. There are about 300 species of turtles.

Together with mammals and birds, reptiles are combined into one group of higher vertebrates.

Where do reptiles live?

For the most part, reptiles lead a terrestrial lifestyle. These are creatures that prefer open landscapes warmed by the sun, including almost devoid of vegetation, waterless deserts. However, many turtles and all crocodiles live in rivers, lakes or swamps. Some snakes and some turtles also live permanently in the seas.

The skin of reptiles, unfortunately, is now used for the production of leather products. It is highly valued, and because of this, many representatives of reptiles suffer. Their future is in our hands.

Crocodile habitats

Crocodiles are common throughout the tropics. Basically, these reptiles are animals living in high-water swamps, lakes and rivers. They usually spend most of the day in the water. Crocodiles come to the coastal shallows in the morning, and also in the late afternoon, in order to bask in the sun. Salty sea water is tolerated by relatively few species. The combed crocodile swims especially far into the open sea - up to 600 km from the coast.

Habitats of tuatara and lizards

Tuataria today survived only on rocky islets located near New Zealand. A special reserve was created here for their sake.

Lizards are distributed almost throughout the planet, except for cold zones. Some types of mountains rise to the border of eternal snow, for example, in the Himalayas - up to a height of 5.5 km above sea level. Most lizards lead a terrestrial lifestyle.

However, some of them climb trees or bushes, such as roundheads. Others may live permanently in trees and are capable of gliding flight. Agamas and geckos living in rocks can move along vertical surfaces. Also, some lizards live in the soil. They usually have no eyes, and their bodies are elongated. The sea lizard lives near the surf line. She has excellent swimming skills. She spends a lot of time in the water, eating seaweed.

Where do snakes and turtles live?

Snakes are everywhere on Earth, except for New Zealand, the polar regions and some oceanic islands. All of them swim well, there are even species that spend almost all or all of their time in the water. These are sea snakes. Their tails are compressed from the sides in a paddle-like manner. Due to the transition of snakes to a burrowing lifestyle, some of them have reduced their eyes and disappeared under the shields, and their tails have also shortened. These are narrow-mouthed snakes and blind snakes.

Freshwater and land turtles are found on many islands, as well as on all continents except Antarctica. Their habitats are very diverse. These are tropical forests, hot deserts, rivers, lakes and swamps, expanses of the ocean and coasts of the seas. Sea turtles spend their entire lives in the water. They come ashore only to lay eggs.

The largest snakes

The largest modern snakes are anacondas (pictured above) and reticulated pythons. In length they reach 10 meters. In Eastern Colombia, a specimen of an anaconda was found, unique in size - 11 m 43 cm. The Brahmin blind is a body length of no more than 12 cm.

Sizes of crocodiles

The largest of the crocodiles are combed and Nile. In length, they reach 7 m. 1.2 m for females and 1.5 m for males is the maximum body length of a smooth-fronted caiman, the smallest among other species of crocodiles.

The largest and smallest turtles

The leatherback sea tortoise is considered the largest of modern turtles. Its length can exceed 2 meters. In the UK, on ​​the coast in 1988, the dead body of a male of this was found, which had a width of 2.77 m and a length of 2.91. Muscovy turtle is the smallest among all species. On average, the length of her carapace is 7.6 cm.

Lizard sizes

Among the lizards, the Virginian round-toed geckos are considered the smallest. Only 16 mm is the length of their bodies (excluding the tail). Without a doubt, the largest lizard is the Komodo dragon (its photo is presented below).

The length of his body reaches three or even more meters. Living in Papua New Guinea, the thin-bodied monitor lizard of El Salvador reaches 4.75 m in length, but about 70% of its length falls on the tail.

Reptile body temperature

Like amphibians, reptiles do not have any kind of constant body temperature. Their life activity therefore depends to a large extent on the ambient temperature. For example, in dry and warm weather, they are especially active and at this time they often catch the eye. On the contrary, in bad weather and cold they become inactive and rarely leave their shelters. At temperatures close to zero, reptiles fall into a stupor. That is why they are few in the taiga zone. There are only about 5 types of them.

Reptiles can control their body temperature simply by hiding from hypothermia or overheating. Hibernation, for example, allows reptiles to avoid the cold, and the heat of the day - night activity.

Breathing Features

Reptiles (a photo of some of them is presented in this article), unlike amphibians, breathe only with their lungs. Their lungs retain a bag-like structure, but reptiles have a much more complex internal structure than amphibians. The folded cellular structure has the inner walls of their lung sacs. They resemble honeycombs. This significantly increases the respiratory surface in reptiles. Unlike amphibians, reptiles do not blow air through their mouths. However, for most of them, breathing of the so-called "suction" type is characteristic. They exhale and inhale air through the nostrils by constricting and expanding the chest. The act of breathing is carried out with the help of the abdominal and intercostal muscles.

However, in turtles, the ribs are immobile due to the presence of a shell, so the species belonging to them have developed a different method of ventilation than other reptiles. They drive air into the lungs by swallowing it or by making pumping movements with their front legs.

reproduction

Reptiles breed on land. At the same time, unlike amphibians, they have direct development, that is, without a larval stage. Reptiles usually lay large eggs rich in yolk with shell and amniotic (embryonic) membranes, which protect embryos from mechanical damage and water loss, and also provide gas exchange and nutrition. By the time of hatching, young reptiles reach a considerable size. These are already miniature copies of adults.

Representatives of reptiles (more than 4 thousand species) are real terrestrial vertebrates. In connection with the appearance of embryonic membranes, they are not associated with water in their development. As a result of the progressive development of the lungs, adult forms can live on land in any conditions. Reptiles living in the form are secondary aquatic, i.e. their ancestors moved from a terrestrial way of life to an aquatic one.

Remember! Reptiles and reptiles are the same class!

Reptiles, or reptiles, appeared at the end of the Carboniferous period, approximately 200 million years BC. when the climate became dry, and in some places even hot. This created favorable conditions for the development of reptiles, which turned out to be more adapted to living on land than amphibians. A number of features contributed to the advantage of reptiles in competition with amphibians and their biological progress. These include:

• Shells around the embryo and a strong shell (shell) around the egg, protecting it from drying out and damage, which made it possible to reproduce and develop on land;
• development of five-fingered limbs;
• improvement of the structure of the circulatory system;
• progressive development of the respiratory system;
• appearance of the cerebral cortex.

The development of horny scales on the surface of the body, which protected from adverse environmental influences, primarily from the drying effect of air, was also important. A prerequisite for the appearance of this adaptation was the release from skin respiration in connection with the progressive development of the lungs.

A typical representative of reptiles can serve as a quick lizard. Its length is 15-20cm. She has a well-defined protective coloration: greenish-brown or brown, depending on the habitat. During the day, lizards are easy to see in a sun-warmed area. At night they crawl under stones, into burrows and other shelters. In the same shelters they spend the winter. Their food is insects.

On the territory of the CIS, the most widespread are: in the forest zone - a viviparous lizard, in the steppe - a quick lizard. The spindle belongs to the lizards. It reaches 30-40 cm, has no legs, which resembles a snake, it often costs her life. The skin of reptiles is always dry, devoid of glands, covered with horny scales, scutes or plates.

The structure of reptiles

Skeleton. The spinal column is already subdivided into the cervical, thoracic, lumbar, sacral and caudal regions. The skull is bony, the head is very mobile. The limbs end in five fingers with claws.

Musculature in reptiles is much better developed than in amphibians.

Digestive system. The mouth leads into the oral cavity, equipped with a tongue and teeth, but the teeth are still primitive, of the same type, they serve only to capture and hold prey. The alimentary canal consists of the esophagus, stomach, and intestines. On the border of the large and small intestines is the rudiment of the caecum. The intestines end with a cloaca. Developed digestive glands: pancreas and liver.

Respiratory system. The respiratory tract is much more differentiated than in amphibians. There is a long trachea, which branches into two bronchi. The bronchi enter the lungs, having the appearance of cellular, thin-walled bags, with a large number of internal partitions. The increase in the respiratory surfaces of the lungs in reptiles is associated with the absence of skin respiration.

excretory system represented by the kidneys and ureters, flowing into the cloaca. It also opens the bladder.

Circulatory system. Reptiles have two circulations, but they are not completely separated from each other, due to which the blood is partially mixed. The heart is three-chambered, but the ventricle is separated by an incomplete septum.

Crocodiles already have a real four-chambered heart. The right half of the ventricle is venous, and the left side is arterial - the right aortic arch originates from it. Converging under the spinal column, they merge into an unpaired dorsal aorta.

Nervous system and sense organs

The brain of reptiles differs from the brain of amphibians in the large development of the hemispheres and the cerebral fornix, as well as in the isolation of the parietal lobes. Appears for the first time, the cerebral cortex. 12 pairs of cranial nerves leave the brain. The cerebellum is somewhat more developed than in amphibians, which is associated with more complex coordination of movements.

At the front end of the lizard's head is a pair of nostrils. The sense of smell in reptiles is better developed than in amphibians.

The eyes have eyelids, upper and lower, in addition, there is a third eyelid - a translucent nictitating membrane, constantly moisturizing the surface of the eye. Behind the eyes is a rounded tympanic membrane. Hearing is well developed. The organ of touch is the tip of a forked tongue, which the lizard constantly sticks out of its mouth.

Reproduction and regeneration

Unlike fish and amphibians, which have external fertilization (in water), reptiles, like all non-amphibian animals, have internal fertilization, in the body of the female. Eggs are surrounded by germinal membranes that ensure development on land.

At the beginning of summer, the female lizard lays 5-15 eggs in a secluded place. Eggs contain nutritional material for the developing embryo, they are surrounded by a leathery shell on the outside. A young lizard, similar to an adult, emerges from the egg. Some reptiles, including some species of lizards, are ovoviviparous (that is, a cub immediately emerges from a laid egg).

Many species of lizards, being grabbed by the tail, break it off with sharp lateral movements. Tail flicking is a reflex response to pain. This should be considered as a device by which lizards are saved from enemies. In place of the lost tail, a new one grows.

Variety of modern reptiles

Modern reptiles are divided into four orders:

• prime lizards;
• scaly;
• Crocodiles;
• Turtles.

prime lizards represented by a single species - tuatara, which refers to the most primitive reptiles. The tuatara lives on the islands of New Zealand.

Lizards and snakes

The scaly ones include lizards, chameleons and snakes.. This is the only relatively large group of reptiles - about 4 thousand species.

Lizards are characterized by well-developed five-fingered limbs, movable eyelids, and the presence of a tympanic membrane. This order includes agamas, poisonous lizards, monitor lizards, real lizards, etc. Most species of lizards are found in the tropics.

Snakes are adapted to crawl on their belly. Their neck is not expressed, so the body is divided into head, trunk and tail. The spinal column, in which there are up to 400 vertebrae, has great flexibility due to additional joints. Belts, limbs and sternum are atrophied. Only a few snakes have preserved a vestige of the pelvis.

Many snakes have two venomous teeth in their upper jaws. The tooth has a longitudinal groove or duct, through which the poison flows into the wound when bitten. The tympanic cavity and membrane are atrophied. The eyes are hidden under transparent skin, without eyelids. The skin of the snake on the surface becomes keratinized and is periodically shed, i.e. molting occurs.

Snakes have the ability to open their mouths very wide and swallow their prey whole. This is achieved by the fact that a number of bones of the skull are connected movably, and the lower jaws are connected in front by a very extensible ligament.

In the CIS, the most common snakes are: snakes, copperheads, snakes. The steppe viper is listed in the Red Book. For her habitat, she avoids agricultural land, and lives on virgin lands, which are becoming less and less, which threatens her with extinction. The steppe viper (like other snakes) feeds mainly on mouse-like rodents, which is certainly useful. Its bite is venomous, but not fatal. She can attack a person only by chance, being disturbed by him.

The bites of poisonous snakes - cobras, efas, gyurzas, rattlesnakes and others - can be fatal to humans. Of the fauna, the gray cobra and sand efa, which are found in Central Asia, are very dangerous, as well as the gyurza, found in Central Asia and Transcaucasia, and the Armenian viper, which lives in Transcaucasia. The bites of the common viper and muzzle are very painful, but usually not fatal to humans.

The science that deals with the study of reptiles is called herpetology.

Recently, snake venom has been used for medicinal purposes. Snake venom is used for various bleeding as a hemostatic agent. It turned out that some drugs derived from snake venom reduce pain in rheumatism and diseases of the nervous system. To obtain snake venom in order to study the biology of snakes, they are kept in special nurseries.

Crocodiles are the most highly organized reptiles with a four-chambered heart. However, the structure of the partitions in it is such that venous and arterial blood are partially mixed.

Crocodiles are adapted to an aquatic lifestyle, in connection with which they have swimming membranes between the fingers, valves that close the ears and nostrils, and a palatine curtain that closes the pharynx. Crocodiles live in fresh waters, come to land to sleep and lay eggs.

Turtles - covered above and below with a dense shell with horny shields. Their chest is motionless, therefore, the limbs take part in the act of breathing - when they are drawn in, the air leaves the lungs, when protruding, it enters them. Several species of turtles live in Russia. Some species are eaten, including the Turkestan tortoise living in Central Asia.

ancient reptiles

It has been established that in the distant past (hundreds of millions of years ago) various types of reptiles were extremely common on Earth. They inhabited the land, water spaces and, less often, the air. Most species of reptiles died out due to climate change (cooling) and the flourishing of birds and mammals, with which they could not compete. Extinct reptiles include orders of dinosaurs, animal-toothed lizards, ichthyosaurs, flying lizards, etc.

Squad Dinosaurs

This is the most diverse and numerous group of reptiles that have ever lived on Earth. Among them were both small animals (the size of a cat and less) and giants, the length of which reached almost 30 m, and their weight was 40-50 tons.

Large animals had a small head, a long neck and a powerful tail. Some dinosaurs were herbivores, others were carnivores. The skin either did not have scales or was covered with a bony shell. Many dinosaurs ran in jumps on their hind limbs, while leaning on their tail, while others moved on all four legs.

Detachment Animals

Among the ancient terrestrial reptiles were representatives of the progressive group, which, in terms of the structure of their teeth, resembled animals. Their teeth were differentiated into incisors, canines and molars. The evolution of these animals went in the direction of strengthening their limbs and belts. In the process of evolution, mammals arose from them.

Origin of reptiles

Fossil reptiles are of great importance, since they once dominated the globe and from them came not only modern reptiles, but also birds and mammals.

Living conditions at the end of the Paleozoic changed dramatically. Instead of a warm and humid climate, cold winters appeared and a dry and hot climate was established. These conditions were unfavorable for the existence of amphibians. However, under such conditions, reptiles began to develop, in which the skin was protected from evaporation, a terrestrial method of reproduction appeared, a relatively highly developed brain, and other progressive features that are given in the characteristics of the class.

Based on the study of the structure of amphibians and reptiles, scientists came to the conclusion that there is a great similarity between them. This was especially true for ancient reptiles and stegocephalians.

• In very ancient lower reptiles, the vertebral column had the same structure as that of stegocephals, and the limbs - like those of reptiles;
• the cervical region of reptiles was as short as that of amphibians;
• the sternum was missing; they did not yet have a real chest.

All this suggests that reptiles are descended from amphibians.

The class of vertebrates that occupy an intermediate position between amphibians and mammals is called reptiles (reptiles). They have a greater resemblance to birds. This class includes the following animals on the list:

• crocodiles;
• turtles;
• snakes;
• lizards;
• dinosaurs (fossil form of animals of the Mesozoic era).

General characteristics of reptiles

Like amphibians, reptiles are cold-blooded creatures. In other words, their body temperature is determined by the surrounding space. To some extent, reptiles are able to regulate their temperature by covering themselves from hypothermia. For example, in the winter season, animals hibernate, and during periods of intense heat, they begin to hunt at night.

Reptiles have hard skin covered with scales. The main task of which is to protect the body from drying out. For example, in turtles the upper protection is provided by a strong shell, crocodiles have hard plates of bone origin on their heads and backs.

Reptiles breathe only through the lungs. In some animal species, the lungs are the same size and equally developed, while in others, such as snakes and lizards, the right lung is larger and is located throughout the body cavity. Turtles have fixed ribs due to the shell, so the ventilation of the body is organized in a different way. Air enters the lungs with the swinging movements of the front legs or with intensive swallowing.

The bone skeleton of reptiles is well developed. The number and shape of the ribs depends on the specific species, but all representatives of the class have them. Almost all turtles have fused bone plates of the shell and spine. snakes have ribs designed for active crawling. In lizards, the ribs serve to support fan-shaped membranes for planning in the air.

Most reptiles have a short tongue that cannot protrude. Snakes and lizards have a long tongue, divided in two, which is able to protrude far from the mouth. For this animal species, these are the most important sense organs.

To protect against the environment, small reptiles have an original coloration. Turtles are protected by a dense shell. Some snakes are venomous.

In terms of reproductive organs, reptiles have similarities with birds. As a rule, reptiles are egg-laying animals. But in some species, until hatching, the eggs remain inside at the site of the oviduct. This type includes some species of lizards and vipers.

Classification of reptiles and their distribution

Modern reptiles are divided into four divisions:

• turtles (about 300 species);
• crocodiles (25 species);
• scaly (about 5500 species of lizards and snakes);
• tuatara (tuatara).

The last detachment belongs to the only representative of beak-winged animals among reptiles.

reptiles distributed throughout the world. The largest number is seen in warm areas. In regions with a cold climate and a lack of woody vegetation, reptiles are practically not found. Representatives of this class live on land, in water (fresh and salty) and in the air.

ancient fossil reptiles

Reptiles have been known since the Carboniferous. They reached their largest sizes in the Permian and Triassic periods. At the same time, an increased multiplication of animals was observed, which populated all new territories. In the Mesozoic era, the dominance of reptiles was overwhelming, both on land and in water. This period is not in vain called the age of reptiles.

Turtles

Turtles are one of the most famous types of reptiles. There are both marine and land representatives of animals. The species is distributed throughout the world. Animals can also keep at home. The oldest representatives of turtles were discovered 200 million years ago. Scientists believe that they originated from a primitive species of cotilosaurs. Turtles are practically harmless animals, they are not dangerous to humans.

Animals of this species have a shell of a bone structure. Outside, it is formed by numerous individual elements of horny tissue, which are connected using plates. Lungs function perfectly for breathing of land turtles. Aquatic representatives of the class breathe with the help of the mucous membrane of the pharynx. The main feature of these animals is longevity. The average age of turtles exceeds the lifespan of any other reptile.

crocodiles

Animals are one of the most dangerous types of reptiles. The origin of crocodiles is associated with ancient reptiles, the size of which exceeded 15 meters in length. Scientists have been able to find the remains of ancient crocodiles on all continents of the globe. Modern representatives of this class have more familiar sizes. But among reptiles, they still remain the largest species.

Almost all the time crocodiles are in the water. Only the ears, nose and eyes of the animal appear on the surface. Crocodiles swim with webbed tails and paws. But at great depths, only single representatives of the class can exist - a combed species. Crocodile nests are located on land. In some cases, they also crawl out of the water to bask.

Reptiles have a strong powerful tail, and are also characterized by a high speed of movement on land. Therefore, crocodiles are extremely dangerous to humans. A sharp, unexpected throw can take people by surprise. Alligators are considered the most dangerous representatives of crocodiles.

Chameleons

This type of lizard is known to almost everyone. Reptiles are known for their unique coloration, which acts as a camouflage. The skin of an animal can change its color depending on environmental conditions. Chameleons live in trees. Some people keep these cute creatures at home.

Reptiles are quite whimsical in care. They need a spacious terrarium, which is equipped with special lamps. You will need a tree, a small pond, floor heating and excellent ventilation. Chameleons feed on insects. Therefore, the owners will also have to take care of their presence.

iguanas

Currently, there are more and more lovers of pets - iguanas. This representative of the lizards also requires special care. Iguanas must be kept in a special terrarium that can maintain a certain temperature regime. From food, domestic iguanas prefer fresh fruits and vegetables, as well as greens. With good care and the creation of optimal living conditions, lizards at home can grow quite large. Maximum iguana weight - 5 kg. Keeping such a pet at home is difficult, it will require a large financial injection, as well as significant labor costs.

Iguanas are among those rare reptile species that molt. Most reptiles experience this period in two days, while in iguanas it stretches for several weeks.

monitor lizards

There are about 70 species of monitor lizards. They live in different areas. The size of the animals is very impressive. In short-tailed monitor lizards, the length is about 20 cm, while in other representatives it is much longer (about 1 meter). Komodo species are considered the largest monitor lizards. Their dimensions reach three meters in length, and their weight is 1500 kg. No wonder these animals are called modern dinosaurs.

Monitor lizards are covered with large scales. They have strong paws with a tenacious grip and powerful long tail. The tongue of the animal is also large in size, at the end it is divided in half. Lizards can only smell with their tongues. The color of animals is dominated by gray and brown shades. Young representatives of the class are often found with spotted or striped scales. Monitor lizards live in regions with a warm climate. They are most commonly found in Australia, Africa and southern Asia. Depending on the habitat, monitor lizards are divided into two types. The first of them lives in a desert area with dry trees and shrubs. And the second is located closer to tropical forests and reservoirs. Some representatives of monitor lizards live on tree branches.

geckos

Unique representatives of reptiles that are able to stick to any surface, even the smoothest. Geckos can climb smooth glass walls, hang from ceilings, and many other interesting things. The lizard is able to stay on the surface with just one paw.

snakes

These are known representatives of reptiles. The main difference from other species is the shape of the body. Snakes have a long body, but do not have paired limbs, eyelids, and an external auditory meatus. Some of these characteristics are present in individual species of lizards, but collectively such characteristics are observed only in snakes.

Serpentine The body is made up of three elements:

• head;
• body;
• tail.

Some representatives have retained rudimentary forms of limbs. A large number of snake species are venomous. They have furrowed or canalized teeth that contain venom. This dangerous liquid comes from the salivary glands of the animal. All internal organs of the snake differ from standard indicators. They have an oblong shape. Animals do not have a bladder. There is in front of the eyes cornea, which was formed from fused eyelids. Diurnal snakes have transverse pupils, while nocturnal snakes have vertical pupils. Because Animals do not have an auditory canal, so only loud sounds are heard for them.

snakes

These are representatives of one of the varieties of snakes. Their main feature is that they are not poisonous. Snakes have bright scales with a large ribbed surface. Animals are common near water bodies. They feed on amphibians and fish. Sometimes snakes manage to catch a bird or a small mammal. Such snakes do not kill their prey, they swallow it whole.

If the snake sensed danger, then it pretending to be dead. And when attacked, a liquid with an extremely unpleasant odor is released from the mouth. Snakes breed on vegetable soils covered with wet moss or natural debris.

The list of modern reptiles can be continued for a very long time. All representatives of the class have certain similarities characteristic of this type of animal, as well as clear differences. Such animals are of great interest to scientists and hobbyists from all over the world. Their unique features can tell a lot.

Amphibians (amphibians). This is a small group of the most primitive terrestrial vertebrates (Fig. 87). Depending on the stage of development, most of them spend part of their lives in water. The ancestors of amphibians were lobe-finned fish that lived in fresh, drying water bodies.

Rice. 87. Amphibians: 1 - newt; 2 - spotted salamander; 3 - proteus; 4 - axolotl (ambistoma larva); 5 - pond frog; 6 - pipa; 7 - worm

In the larval stage (tadpoles), amphibians are very similar to fish: they retain gill breathing, have fins, a two-chambered heart, and one circle of blood circulation. Adult forms are characterized by a three-chambered heart, two circles of blood circulation, two pairs of limbs. The lungs appear, but they are poorly developed, so additional gas exchange occurs through the skin (see Fig. 85). Amphibians live in warm, humid places, especially common in the tropics, where they have suitable climatic conditions.

These are separate animals. They are characterized by external fertilization and development in water. From the eggs of a tailless amphibian, such as a frog, a tailed larva emerges - a tadpole with long fins and branched gills. As it develops, the forelimbs appear, then the hind limbs, and the tail begins to shorten. Branched gills disappear, gill slits (internal gills) appear. From the anterior part of the digestive tube, lungs are formed, as they develop, the gills disappear. There are corresponding changes in the circulatory, digestive and excretory systems. The tail resolves, and the young frog comes to land. In caudate amphibians, the gills remain much longer (sometimes for a lifetime), the tail does not resolve.

Amphibians feed on animal food (worms, mollusks, insects), but the larvae living in the water can be herbivorous.

There are three groups of amphibians: caudate(newt, salamander, ambistoma), tailless(toads, frogs) legless, or worms(fish snake, worm).

Tailed amphibians the most primitive. They live in and near water, and their limbs are usually poorly developed. Some have feathery gills throughout their lives.

Ambystoma larva - axolotl even starts breeding before reaching the adult stage. Salamanders are the most numerous.

Worms- a very small family. They have no limbs, the body is elongated, reminiscent of a worm or a snake.

The most prosperous group tailless amphibians. They have a short body and well developed limbs. During the breeding season, they "sing" - make various sounds (croak).

Reptiles (reptiles). Reptiles are terrestrial vertebrates. They adapted well to life on land and displaced many of their amphibian ancestors. Reptiles have a three-chambered heart. They begin to separate arterial and venous blood due to the appearance of an incomplete septum in the ventricle of the heart; the nervous system is better developed than that of amphibians: the hemispheres of the brain are much larger (see Fig. 85). The behavior of reptiles is much more complex than that of amphibians. In addition to congenital unconditioned, they also form conditioned reflexes. Digestive, excretory and circulatory systems open into cloaca- part of the intestine.

The body of reptiles is covered with scales. It is formed in the thickness of the skin - the epidermis - and protects the body from drying out. Some species shed their scales during molting (snakes, lizards). The lungs of reptiles are much larger and more voluminous than those of amphibians, due to the cellularity.

Reptiles are dioecious animals. Fertilization is internal. The female lays eggs in the sand or in the soil in small depressions, covered with a leathery shell. Even among aquatic inhabitants, the development of eggs takes place on land. Some species are characterized by live birth.

Reptiles reached their greatest prosperity in the Mesozoic era, about 100-200 million years ago, therefore this era is called the era of reptiles. There were a huge number and variety of them: dinosaurs - on land, ichthyosaurs - in water, pterosaurs - in the air. Among them were species of enormous size, as well as rather small forms, the size of a cat. Almost all of them died out about 70 million years ago. The cause of extinction is still not fully understood. There are several hypotheses: a sudden sharp change in climate, the fall of a giant meteorite, etc. But all of them do not fully explain this mystery.

Currently, there are four main groups: turtles, snakes, lizards and crocodiles (Fig. 88).

Rice. 88. Reptiles: 1 - steppe gecko; 2 - agama; 3 - eared round head; 4 - frilled lizard; 5 - gray monitor lizard; 6 - spectacled snake; 7 - rattlesnake; 8 - already

characteristic feature turtles is the presence of a shell, consisting of bone plates and covered with a horny substance. Representatives of this group can live both on land and in water. Giant and elephant tortoises (up to 110 cm long) are the largest of those living on land. They are common in the Galopogos Islands of the Pacific Ocean, Madagascar, the islands of the Indian Ocean.

Sea turtles are much larger (up to 5 m), have flipper-like legs. They live in water all their lives, but they lay their eggs on land.

lizards very varied. This is the most prosperous group. These include chameleons, geckos, iguanas, agamas, roundheads, monitor lizards and true lizards. Most lizards are characterized by an elongated body, a long tail, and well-developed limbs. Some (yellow bellies) have lost limbs, they resemble snakes.

At snake the main feature is a long, limbless body. They are crawling animals. All snakes are predators; they swallow prey whole or strangle it, squeezing it in the rings of their bodies. The poisonous glands (modified salivary glands) open with a duct at the base of the poisonous tooth. Snakes include: viper, gyurza, cobra, python, boa constrictor, as well as snakes - non-poisonous representatives of this group.

crocodiles Of all reptiles, they are closest to mammals. Their heart can be called four-chambered, there is a bony palate, air enters through the nostrils into the back of the mouth. In terms of the structure of the oral cavity and the location of the tongue, they are closer to mammals than to other reptiles. These are rather large tailed animals that live in the water, along the banks of rivers. On land, they move slowly, but they are excellent swimmers. Females lay calcareous-shelled eggs on land in small pits. They are characterized by caring for offspring: the female guards the clutch and takes care of the cubs.

Reptiles live mainly in warm climates: tropics, subtropics, wet and dry places: deserts, swamps, forests. Their food is also varied: plants, insects, worms, mollusks, and large individuals eat birds and mammals. All reptiles swallow their food whole. Many species, feeding on agricultural pests (insects, rodents), are of great benefit to humans. Snake venom is used to make many medicines. Shoes and handbags are made from the skin of snakes and crocodiles, which previously led to the mass extermination of animals. Currently, many species are under protection, they are grown on farms and in nurseries.

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§ 62. Chordates. Fish§ 64. Birds

Often only snakes are considered reptiles, but animals such as lizards, chameleons and crocodiles belong to this class.

Contrary to popular belief, reptiles, or reptiles, are not covered in mucus. In snakes and other representatives of this class, the body is covered with horny scales or scutes and is dry to the touch.

Scales are derivatives of the skin, but in some species they are almost invisible. In turtles, thickened scales form a hard shell; Crocodiles have more flexible armor. The scaly cover protects from predators and protects the body from drying out, but its functions are not limited to this. Some lizards have scaly collars, or ridges, which are raised when courting or to scare off an enemy. Geckos can walk on the ceiling thanks to special brushes on their fingers. The fringe of jagged scales on the fingers of desert lizards plays the same role as snowshoes, allowing them to run on loose, loose sand.

large reptiles

Dinosaurs were the largest reptiles. But modern reptiles are certainly far from them. Today, the Madagascar crocodile and the Gangetic gharial are considered to be such, which reach a length of 9 m. Snakes such as pythons and anacondas are not so massive, but are comparable in length to crocodiles. Of the poisonous snakes, the largest is the king cobra living in the Asian tropics, it reaches a length of 5.5 m and also has a bad temper. The largest lizard is the 4-meter Komodo monitor lizard, which easily copes with a pig and other large prey. Sea leatherback turtle, swimming at a speed of 30 km / h, weighs about a ton.

cold blooded animal

Unlike birds and animals, reptiles are cold-blooded animals, which means that they do not have a mechanism for regulating body temperature, which changes with the temperature of the environment. When the air is colder than + 18°C, the vital activity of most reptiles decreases sharply; at a temperature of +51 ° C, they die from overheating. Reptiles are able to influence their body temperature to some extent. In the morning they like to bask in the sun, in the midday heat they rise high on their feet so that the air cools the body. Some hide in the heat, while others cool down by breathing frequently. Cold-bloodedness is associated with energy savings. A rabbit weighing 1 kg spends 80% of the energy received from food on maintaining body temperature and therefore must eat more than an iguana weighing 10 times more.

snakes

If you carefully observe the snake, it becomes clear that the absence of legs does not interfere with it at all, and sometimes even helps. Snakes easily climb into holes and crevices, move over rough terrain and squeeze through dense thickets. To move quickly, snakes squirm in an S-shape. But they can also smoothly slide forward, stretching out into a string and alternately pulling the scales on the ventral side up and forward. Many species are able to climb trees. Having climbed a tree, the snake can travel long distances, throwing itself like a bridge from branch to branch.

Do snakes lay eggs?

The structure of the egg is perfectly adapted for the initial stages of the development of a living organism. Reptile eggs have a dense shell that protects the embryo from drying out and at the same time allows oxygen to pass through. From the inside, the shell is lined with a thin shell, densely permeated with blood vessels. This shell plays the role of an organ of respiration and excretion. The shell protects the embryo from mechanical damage and temperature fluctuations. The yolk is the food of the developing organism.

Despite all the advantages of the egg, some reptiles are viviparous. Sea turtles and many other aquatic reptiles come out of the sea to lay their eggs on land. However, their eggs and juveniles (and sometimes adults) become easy prey for terrestrial predators. Sea snakes, on the other hand, breed in the ocean without the dangers of traveling to land.

Why does a lizard lose its tail?

The tail of lizards, as a rule, serves as a steering wheel, allowing them to quickly change direction. Lizards running on their hind legs use their tail as a counterweight. Chameleons wrap their tails around tree branches, just like monkeys do. In some desert lizards, the tail is equipped with spikes and serves as a weapon. Sometimes a lizard loses its tail to its advantage. When a predator grabs a lizard by the tail (which can be brightly colored), it breaks off, and its owner flees. The detached tail continues to writhe, diverting the attention of the pursuer from the fleeing victim. After 1-2 months, a new tail grows.

The care of most reptiles about offspring is limited to the fact that they lay eggs in places favorable for their development, then they do not show any interest in them. Crocodiles are real crocodiles, alligators, caimans and gharials are an exception. The female lays her eggs in a specially dug hole or in a pile of earth and rotting leaves. Having made a clutch, she guards it throughout the entire period of incubation, periodically turning the eggs over to maintain even temperature and humidity. When the babies hatch, the mother, having heard their squeak, helps them get out, and sometimes transfers them to the water. In some species, “playgrounds” are organized in swamps, where young animals are guarded for several months. Sometimes males take part in caring for children.