What kind of reptiles are there? Class reptiles or reptiles

Representatives of reptiles (more than 4 thousand species) are true terrestrial vertebrates. Due to the appearance of the 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 species are secondary aquatic, i.e. their ancestors switched from a terrestrial lifestyle 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 traits contributed to the advantage of reptiles in competition with amphibians and their biological progress. These include:

• The membranes 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, protecting against adverse influences, was also important. environment, first of all, from the drying effect of air. The prerequisite for the appearance of this device was liberation from skin respiration due to the progressive development of the lungs.

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

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

The structure of reptiles

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

The muscles of reptiles are much better developed than those of amphibians.

Digestive system . Mouth leads to oral cavity, equipped with a tongue and teeth, but the teeth are still primitive, of the same type, and serve only for capturing and holding prey. The alimentary canal consists of the esophagus, stomach, and intestines. At the border of the large and small intestines the rudiment of the cecum is located. The intestines end in a cloaca. Digestive glands are developed: pancreas and liver.

Respiratory system. Airways much more differentiated than in amphibians. There is a long trachea that branches into two bronchi. The bronchi enter the lungs, which look like cellular, thin-walled sacs, with big amount internal partitions. The increase in the respiratory surfaces of the lungs in reptiles is associated with the lack of cutaneous respiration.

Excretory system represented by the kidneys and ureters flowing into the cloaca. The bladder also opens into it.

Circulatory system . Reptiles have two circles of blood circulation, but they are not completely separated from each other, due to which the blood is partially mixed. The heart has three chambers, but the ventricle is divided by an incomplete septum.

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

Nervous system and sensory organs

The brain of reptiles differs from the brain of amphibians in the greater development of the hemispheres and cerebral vault, as well as the separation of the parietal lobes. Appears for the first time, the cerebral cortex. 12 pairs of cranial nerves arise from 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 there 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 that constantly moisturizes the surface of the eye. Behind the eyes is a rounded eardrum. Hearing is well developed. The organ of touch is the tip of the 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-amphibious animals, have internal fertilization, in the body of the female. The eggs are surrounded by embryonic membranes that enable development on land.

The female lizard quickly lays 5-15 eggs in a secluded place at the beginning of summer. The eggs contain nutritional material for the developing embryo and are surrounded on the outside by a leathery shell. A young lizard emerges from the egg, looking like an adult. Some reptiles, including some species of lizards, are ovoviviparous (i.e., a baby immediately emerges from a laid egg).

Many species of lizards, when grabbed by the tail, break it off with sharp lateral movements. Throwing back the tail is a reflex response to pain. This should be considered as an adaptation thanks to which lizards escape from enemies. A new one grows in place of the lost tail.

Diversity of modern reptiles

Modern reptiles are divided into four orders:

• Protolizards;
• Scaly;
• Crocodiles;
• Turtles.

Protolizards represented by a single type - tuateria, which is one of the most primitive reptiles. The tuateria lives on the islands of New Zealand.

Lizards and snakes

Scaly animals include lizards, chameleons and snakes. This is the only relatively numerous group of reptiles - about 4 thousand species.

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

Snakes are adapted to crawling on their belly. Their neck is not pronounced, so the body is divided into head, torso and tail. The spinal column, which contains up to 400 vertebrae, is highly flexible thanks to additional articulations. The belts, limbs and sternum are atrophied. Only some snakes have preserved a rudimentary pelvis.

Many snakes have two poisonous teeth on 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 snake's skin becomes keratinized on the surface and is periodically shed, i.e. moulting 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 skull bones are movably connected, and mandibles They are connected in front by a very tensile ligament.

The most common snakes in the CIS are snakes, copperheads, snakes. The steppe viper is listed in the Red Book. For its habitat, it avoids agricultural lands, but lives on virgin lands, which are becoming less and less, which threatens it with extinction. Feeds steppe viper(like other snakes) are predominantly mouse-like rodents, which is certainly useful. Its bite is poisonous, but not fatal. She can attack a person only by accident, being disturbed by him.

The bites of poisonous snakes - cobra, epha, viper, rattlesnake and others - can be fatal to humans. Of the fauna, the gray cobra and sand epha, which are found in Central Asia, as well as the viper, found in Central Asia and Transcaucasia, the Armenian viper, living in Transcaucasia. The bites of the common viper and copperhead are very painful, but usually not fatal to humans.

The science that studies reptiles is called herpetology.

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

Crocodiles are the most highly organized reptiles, having 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, and therefore have swimming membranes between the toes, valves that close the ears and nostrils, and a velum that closes the pharynx. Crocodiles live in fresh waters, come to land to sleep and lay eggs.

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

Ancient reptiles

It has been established that in the distant past (hundreds of millions of years ago) they were extremely common on Earth. different kinds reptiles. They inhabited land, water, and less often air. Most species of reptiles became extinct due to climate change (cold temperatures) and the rise of birds and mammals, with which they could not compete. Extinct reptiles include orders of dinosaurs, wild-toothed lizards, ichthyosaurs, flying lizards, etc.

Dinosaur Squad

This is the most diverse and numerous group of reptiles that has ever lived on Earth. Among them were both small animals (the size of a cat and smaller) and giants, whose length reached almost 30 m and weight - 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 had no scales or was covered with a bone shell. Many dinosaurs ran galloping on their hind limbs, leaning on their tail, while others moved on all four legs.

Squad Animal-toothed

Among the ancient land reptiles there were representatives of a progressive group, which resembled animals in the structure of their teeth. 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 have 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 established. These conditions were unfavorable for the existence of amphibians. However, under such conditions, reptiles began to develop, whose skin was protected from evaporation, a terrestrial method of reproduction, a relatively highly developed brain and other progressive characteristics appeared, which are given in the characteristics of the class.

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

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

All this suggests that reptiles evolved from amphibians.

Larval stage. Most reptiles are oviparous, although there are also viviparous species.

Reptiles range in size from the tiny gecko ( Sphaerodactylus ariasae), with a maximum body length of about 18 mm, to the saltwater crocodile ( Crocodylus porosus), which can reach 6 m in length and weigh more than 1000 kg.

Reptiles are common to all except . Depending on the species, they can live both on land and in water.

The modern classification identifies the following 4 orders of reptiles:

Order Beakheads

Beakheads ( Rhynchocephalia) - an order of lizard-like reptiles that includes only one living genus, tuatara (tuatara). In turn, this genus ( Sphenodon) includes two types: Sphenodon punctatus And Sphenodon guntheri. According to some sources, the genus contains one species Sphenodon punctatus, which is divided into two subspecies - Sphenodon punctatus punctatus And Sphenodon punctatus guntheri. Representatives of the order live only in some areas of New Zealand.

Despite the current lack of diversity, the squad Rhynchocephalia included at one time a large number of genera and families, and it can be traced back to .

Hatteria grows up to 80 cm in length, from head to tail, and weighs up to 1.3 kg. This animal has a spiny crest along its back, which is especially pronounced in males. Tuatara are also distinguished by the presence of a pronounced parietal eye (third eye). Animals can hear, although there is no external ear and hatteria have unique skeletal features.

Tuatara, like many of New Zealand's endemic animals, are endangered due to loss and introduction of invasive species.

Squad Crocodiles

Saltwater crocodile

Crocodiles ( Crocodylia) - a detachment of large, predatory reptiles, which includes 24 species. This includes: caimans, alligators, real crocodiles, gharials, etc. Crocodiles have powerful jaws with a large number of conical teeth and short paws, with claws, and webbed toes. They have a unique body shape that allows the eyes, ears and nostrils to be above the surface of the water while most of the animal's body is submerged. The tail of crocodiles is long and massive. The skin of these reptiles is thick and covered with horny scales.

Crocodiles are the closest living relatives. A wide variety of fossil crocodiles have been discovered that lived for more than 200 million years, in the late. They are the largest and heaviest of modern reptiles. The largest representatives of the order are the Nile crocodile ( Crocodylus niloticus) And saltwater crocodile (Crocodylus porosus) - reach a body length of up to 6 m and a weight of more than 1000 kg. For comparison, the smallest representatives of the order are smooth-faced caimans ( Paleosuchus) and blunt-snouted crocodiles ( Osteolaemus tetraspis), have a length of about 1.7 m.

Crocodiles are found mainly in the low-lying, humid tropics and...

Turtle Squad

Spurred turtle

Turtles ( Testudines) - a detachment of reptiles, including about 300 species of turtles that live on land and in water (fresh and salt) on all continents except.

The earliest known members of this order existed about 220 million years ago, making turtles one of the oldest reptiles. Some species are endangered.

Turtles range in size from less than 10 cm ( Sternotherus depressus) up to more than 2.5 m, (leatherback turtle - Dermochelys coriacea). Some species live in cold climates with a breeding season of only about three months; others live in tropical regions and breed year-round. Some turtles rarely see water, while others spend virtually their entire lives in it, whether alone small pond or .

The shell is a unique adaptation of turtles that protects them from predators. It has various modifications and shapes to meet the protection, feeding and movement needs of turtles.

Order Scaly

Anaconda

Scaly ( Squamata) - the most numerous order of reptiles, including lizards, chameleons, moths and snakes. Consisting of over 10,000 species, squamates are also the second largest extant order, after the Perciformes (containing about 41% bony fishes).

Representatives of the order are distinguished by their skin consisting of horny scales. They also have movable square bones. This is especially noticeable in snakes, which are able to open their mouths very wide to swallow relatively large prey.

Squamates come in a variety of sizes, from the 16 mm dwarf gecko ( Sphaerodactylus ariasae) to more than 5 m green anaconda ( Eunectes murinus). The order also includes the now extinct mosasaurs, which reached a body length of about 15 m. Among other reptiles, squamates are most closely related to beaked mosasaurs, which closely resemble lizards.

Reptiles are animals belonging to the class of vertebrates. They occupy a place between amphibians and mammals. Another name for them is reptiles.

Many reptiles are so unique that even non-professional biologists may be interested in studying this class.

Reptiles

Reptiles include the following animals:

• Dinosaurs (fossil form);
• Scaly (lizards, snakes);
• Turtles;
• Hatteria;
• Crocodiles.

Like amphibians, reptiles are cold-blooded creatures. To put it another way, their body temperature depends on the environment. Some of them, for example, hibernate in winter, and during intense heat they switch to night hunting. Reptiles have tough, scaly skin that protects the animal's body from drying out. The turtle's top protection is a strong shell, while the crocodile has plates of bone origin on its back and head.

Reptiles breathe through their lungs. Some animals have the same lung size and equal degree of development, and in snakes and lizards the right lung is located throughout the body cavity and has big size. Since turtles have fixed ribs due to their shell, air enters the lungs during the movement of the front legs, or when the turtle swallows intensively.

The bony skeleton of representatives of this class is quite well developed. Each individual has ribs, the shape and number of which depend on the specific species. Almost all turtles have fused bony plates of the shell and spine. Snakes' ribs are very flexible, which allows them to crawl. And lizards have fan-shaped membranes, so their ribs support them, which helps them glide in the air. Many species of reptiles have a short tongue that does not protrude. But snakes and lizards long tongue, extending far from the mouth and divided into two parts.

Reptiles also have a number of abilities that protect them from their environment. For example, small reptiles have original colors. Turtles are under the reliable protection of a dense shell. Some snakes have poisonous saliva.

Basically, reptiles are oviparous animals, which makes them similar to birds. But in some species, eggs are located in the oviduct until hatching. This type includes several species of lizards and vipers.

Dinosaurs are descendants of modern reptiles

From the lessons of history and biology we know that reptiles appeared back in Carboniferous period. The largest individuals appeared in the Permian and Triassic periods, at the same time there was an increase in reproduction and the colonization of new territories by animals. Mesozoic era was called the age of reptiles, because their dominance was overwhelming both on land and in water.

Types of lizards

One of the most famous and unique species of lizards is the chameleon. Its uniqueness lies in its coloring, which performs a camouflage function - the color of the skin can change depending on environmental conditions. Their habitat is trees. Some people keep these animals as pets, but the chameleon is very demanding to care for. The main condition for his comfortable living is a spacious terrarium equipped with special lamps. It will also be necessary to purchase wood, there must be a small pond, heated floors and good ventilation. Their diet mainly consists of insects.

In addition to chameleons, people have recently increasingly acquired iguanas as pets. Representatives of this species of lizard also require special care. They must be kept in a special terrarium, in which it is necessary to maintain a certain temperature regime. They feed mainly on fruits, vegetables and herbs. Under good home conditions, lizards can grow up to 5 kg. Keeping such an animal is very difficult and very expensive. Iguanas are a species of animal that undergoes a molting process that lasts for several weeks.

One of the largest representatives of lizards is the monitor lizard. Its size is very impressive: the short-tailed monitor lizard reaches 20 cm in length, and its other representatives are much larger - about 1 meter. Komodo dragons are considered the largest. Their size reaches 3 m, and their body weight reaches one and a half thousand kilograms; they are also called modern dinosaurs. They have a tenacious grip and powerful long tail. Covered with large gray-brown scales. The animal's tongue is also very large, divided in half. He smells only with his tongue.

They live in Australia, Africa, South Asia - that is, in regions with a warm climate. They are divided into two types, depending on their habitat. The former prefer desert areas with dry trees and shrubs, while the latter are located near bodies of water and tropical forests. Some representatives of monitor lizards prefer to live on tree branches.

Another unique representative of reptiles are geckos, whose peculiarity is gluing to any surface, even the smoothest: ceiling, smooth glass walls. This type of lizard is able to stay suspended with just one leg.

Description of snakes

The main difference between a snake and other reptile species is its body shape. They have a long body, but do not have paired limbs, eyelids or an external auditory canal. Some of these characteristics have individual species lizards, but only the snake exhibits all these signs together.

The snake's body consists of:

• Heads;
• Bodies;
• Tail.

A considerable number of snakes are poisonous. They have grooved or channeled teeth that contain venom. All internal organs of the snake are oblong in shape, and there is no bladder. The cornea on the eyes is formed from fused eyelids. The location of the pupil also depends on the type of life snakes lead: in night snakes the pupil is in a vertical position, in daytime snakes it is in a horizontal position. They only hear loud sounds because they do not have an ear canal.

The snake is a snake belonging to the class of reptiles. Its main feature is that it is poisonous. It has large ribbed scales of bright color. The habitat of snakes is near water bodies. They reproduce on plant soils covered with moss or natural debris. Their main diet includes amphibians and fish, and with rare exceptions, if they can be caught, birds or a small mammal. They swallow their prey whole. When it senses danger, the snake pretends to be dead, and if it is attacked, a very unpleasant odor liquid is released from its mouth.

Crocodiles - amphibians or reptiles

The crocodile is the largest of modern reptiles and the most dangerous. Ancient representatives of this species exceeded a length of more than 15 meters. Judging by the remains found, crocodiles lived on all continents. Modern reptiles are significantly smaller than their ancestors, but they are still the largest reptiles.

They spend most of their lives in water. Only the organs of vision, hearing and nose remain on the surface. The tail and feet are webbed, making them excellent swimmers. However, they prefer to be in shallow water. They come to land to breed and to warm themselves. They have a significant tail size and are very fast both in water and on land. They attack stealthily and unexpectedly, therefore they are especially dangerous for humans.

Features of the tuateria

The tuatara, best known as the tuatara, is a very rare reptile that is the only representative of its species. Belongs to the ancient order of beak-headed animals and the wedge-toothed family.

An ignorant person may confuse the hatteria with a fairly large lizard. But there are a number of differences between representatives of these two species of reptiles. Body weight of adult males twice the mass of a mature female of this species and is about a kilogram. The length of the body including the tail is about 65-75 cm. If you find a picture (photo) on the Internet, you can see that the animal has an olive-green or greenish-gray color on the sides of the body. There are yellowish spots of varying sizes on the limbs.

The common similarity with the iguana is that a crest runs along the entire surface of the back from the back of the head to the tail, which is represented by triangular plates. Hence another name for this animal - Tatar, which translates as “prickly”.

Despite the fact that the tuateria is very similar in appearance to a lizard, it has long been classified as a beaked fish. This is explained by the structure of the animal’s body, and in particular, the head area. The structure of the hatteria's skull has an interesting feature - the upper jaw, skull cap and palate have pronounced mobility relative to the braincase.

Hatteria has been proven to have originated from a terrestrial vertebrate- a lobe fish, from which it inherited this feature. Particular attention is also paid to the presence of a parietal or third eye in the reptile, located in the back of the head. This organ has light-sensitive cells and a lens and completely lacks the muscles that are responsible for focusing the eye. With age, the parietal eye becomes overgrown and is practically indistinguishable in adults.

Animals are active only at low temperatures; in hot weather they hide in deep burrows. They do not lead a very active lifestyle, and hibernate in winter. Another feature of representatives of the beaked order is that they swim very well and can hold their breath for up to an hour. The lifespan of these animals in the wild is about 100 years.

Hatteria living in wildlife, has an excellent appetite. Her diet includes:

• Insects;
• Frogs;
• Spiders;
• Mice;
• Lizards.

She also destroys bird nests, eats eggs and newborn chicks, and catches small birds.

At the height of summer, which begins in the Southern Hemisphere around the last ten days of January, this reptile begins the process of active reproduction.

After fertilization female after nine or ten months lays eggs (their number is from eight to fifteen) in burrows, burying them with earth and stones, after which they incubate. Incubation period takes about fifteen months.

A group of scientists from one of the leading Universities of Wellington conducted unusual and interesting experiments, during which they were able to obtain the relationship between temperature indicators and the sex of the hatched offspring of the tuataria. If incubation occurs at a temperature of 18 o C, then females are born, and at a temperature of 22 o C only males are born.

And this is not the entire list of modern reptiles. It can be continued ad infinitum. All representatives of the class share certain similarities, but they also have many clear differences. These animals are of massive interest to scientists and hobbyists around the world. There are about 80 species of reptiles in Russia.

Scales on the skin of a lizard

The girdle of the forelimbs is similar to the girdle of amphibians, differing only in the stronger development of ossification. The forelimb of reptiles consists of the shoulder, forearm and hand. Posterior - from the thigh, lower leg and foot. Claws are located on the phalanges of the limbs.

Muscular system

The brain is located inside the skull. A number of important features distinguish the brain of reptiles from the brain of amphibians. They often talk about the so-called sauropsid type of brain, which is also inherent in birds, in contrast to the ichthyopsid type in fish and amphibians.

There are five sections of the reptile brain.

• The forebrain consists of two cerebral hemispheres, from which the olfactory lobes extend. The surface of the cerebral hemispheres is absolutely smooth. In the medullary vault of the hemispheres, a distinction is made between the primary vault - the archipallium, which occupies most of the roof of the hemispheres, and the rudiments of the neopallium. The floor of the forebrain mainly consists of the striatum.
• The diencephalon is located between the forebrain and midbrain. The parietal organ is located in its upper part, and the pituitary gland is located on the lower side. The bottom of the diencephalon is occupied by the optic nerves and their chiasm.
• The midbrain is represented by two large anterior hills - the optic lobes, as well as small posterior hills. The visual cortex is more developed than in amphibians.
• The cerebellum covers the anterior part of the medulla oblongata. It is larger compared to the cerebellum of amphibians.
• The medulla oblongata forms a bend in the vertical plane, which is characteristic of all amniotes.

12 pairs of cranial nerves arise from the brain. In the spinal cord, the division into white and gray matter is more distinct than in amphibians. Segmental spinal nerves arise from the spinal cord to form the typical brachial and pelvic plexus. The autonomic nervous system (sympathetic and parasympathetic) is clearly expressed in the form of a chain of paired nerve ganglia.

Sense organs

Reptiles have five main sense organs:

• The organ of vision, the eyes, are more complex than those of frogs: the sclera contains a ring of thin bone plates; a ridge extends from the back wall of the eyeball, protruding into the vitreous body; in the ciliary body, striated muscles are developed, which allows not only to move the lens, but also to change its shape, thus achieving focus during the process of accommodation. The organs of vision have adaptations to work in the air environment. The lacrimal glands protect the eye from drying out. The outer eyelids and nictitating membrane perform a protective function. In snakes and some lizards, the eyelids fuse to form a transparent membrane. The retina of the eye can contain both rods and cones. Nocturnal species have no cones. In most diurnal species, the range of color vision is shifted to the yellow-orange part of the spectrum. Vision is crucial among the sense organs of reptiles.
• The olfactory organ is represented by the internal nostrils - choanae and the vomeronasal organ. Compared to the structure of amphibians, the choanae are located closer to the pharynx, which makes it possible to breathe freely while food is in the mouth. The sense of smell is better developed than that of amphibians, allowing many lizards to find food located under the surface of the sand at a depth of 6-8 cm.
• The organ of taste is the taste buds, located mainly in the pharynx.
• The thermal sensory organ is located on the facial fossa between the eye and nose on each side of the head. Especially developed in snakes. In pit snakes, thermolocators can even determine the direction of the source of thermal radiation.
• The organ of hearing is close to the organ of hearing of frogs; it contains the inner and middle ear, equipped with a tympanic membrane, an auditory ossicle - the stirrup, and an eustachian tube. The role of hearing in the life of reptiles is relatively small; the hearing is especially weak in snakes, which do not have an eardrum and perceive vibrations traveling along the ground or in water. Reptiles perceive sounds in the range of 20-6000 Hz, although most hear well only in the range of 60-200 Hz (for crocodiles 100-3000 Hz).
• The sense of touch is clearly expressed, especially in turtles, which can feel even a light touch on the shell.

Respiratory system

Reptiles are characterized by suction-type breathing by expanding and contracting the chest with the help of intercostal and abdominal muscles. The air entering through the larynx enters the trachea - a long breathing tube, which at the end is divided into bronchi leading to the lungs. Like amphibians, the lungs of reptiles have a sac-like structure, although their internal structure is much more complex. The inner walls of the lung sacs have a folded cellular structure, which significantly increases the respiratory surface.

Since the body is covered with scales, reptiles do not have cutaneous respiration, and the lungs are the only respiratory organ.

Circulatory system

Circulatory system of reptiles

Like amphibians, most reptiles have a three-chambered heart, consisting of one ventricle and two atria. The ventricle is divided by an incomplete septum into two halves: upper and lower. With this design of the heart, a gradient (difference) in the amount of blood oxygen is established in the slit-like space around the incomplete ventricular septum. After the atria contract, arterial blood from the left atrium enters the upper half of the ventricle and displaces venous blood flowing from the right part of the ventricle into the lower half. Mixed blood appears in the right side of the ventricle. When the ventricle contracts, each portion of blood rushes to the nearest hole: arterial blood from the upper half - into the right aortic arch, venous blood from the lower half - into the pulmonary artery, and mixed blood from the right part of the ventricle - into the left aortic arch. Since it is the right aortic arch that carries blood to the brain, the brain receives the most oxygen-rich blood. In crocodiles, the septum completely divides the ventricle into two halves: the right - venous and the left - arterial, thus forming a four-chambered heart, almost like in mammals and birds

In contrast to the common arterial trunk of amphibians, reptiles have three independent vessels: the pulmonary artery, and the right and left aortic arches. Each aortic arch bends back around the esophagus, and when they meet each other, they unite to form the unpaired dorsal aorta. The dorsal aorta stretches back, sending arteries along the way to all organs. From the right arch of the aorta, extending from the left arterial ventricle, the right and left carotid arteries branch off with a common trunk, and both subclavian arteries, carrying blood to the forelimbs, branch off from the right arch.

A complete division into two independent circles of blood circulation in reptiles (including crocodiles) does not occur, since venous and arterial blood mix in the dorsal aorta.

Like fish and amphibians, all reptiles are cold-blooded animals.

Digestive system

Due to the variety of food available for nutrition, the digestive tract of reptiles is much more differentiated than that of amphibians.

Excretory system

The kidneys of reptiles differ significantly from the kidneys of fish and amphibians, which have to solve the problem of getting rid of a constant excess of water in the body. Instead of the trunk kidneys of amphibians (mesonephros), the kidneys of reptiles (metanephros) are located in the pelvic region on the ventral side of the cloaca and on its sides. The kidneys are connected to the cloaca through the ureters.

The thin-walled, stalk-shaped bladder is connected to the cloaca by a thin neck on its ventral side. In some reptiles the bladder is underdeveloped (crocodiles, snakes, some lizards).

Reproductive system

Reptiles are dioecious animals.

Male reproductive system consists of a pair of testes that are located on the sides lumbar region spine. A seminal canal extends from each testis, which flows into the Wolffian canal. With the appearance of the trunk bud in wolf reptiles, the canal in males acts only as a vas deferens and is completely absent in females. The Wolffian canal opens into the cloaca, forming the seminal vesicle.

Female reproductive system represented by ovaries, which are suspended on the mesentery to the dorsal side of the body cavity on the sides of the spine. The oviducts (Müllerian canals) are also suspended on the mesentery. The oviducts open into the anterior part of the body cavity with slit-like openings - funnels. The lower end of the oviduct opens into the lower part of the cloaca on its dorsal side.

Lifestyle

Development

Fertilization is internal.

Nutrition

Most reptiles are carnivores. Some (for example, agamas, iguanas) are characterized by a mixed diet. There are also almost exclusively herbivorous reptiles (land turtles).

Economic importance

The importance of reptiles for humans is relatively small. The skin of crocodiles, large snakes and lizards is used in the leather industry to make suitcases, belts, shoes, etc., but these items are of an exclusive nature, being a luxury item. The meat of some turtles and eggs are eaten. Snake venom is used in medicine. Many snakes are useful in exterminating rodents, and lizards are useful in exterminating insects. Some species of reptiles are kept as pets.

They pose a great danger to people Poisonous snakes, especially in tropical countries. Large crocodiles are dangerous to humans and cause damage to livestock. Many turtles harm fisheries.

Origin of reptiles

The first representatives of reptiles - cotylosaurs - have been known since the Middle Carboniferous. By the end of the period, animal-like reptiles appeared, which in the Permian period settled almost throughout the entire land, becoming the dominant group among reptiles. In the Mesozoic era, reptiles flourished, and the greatest diversity was observed among the representatives. The development of sea and river reservoirs, as well as air space, is taking place. In the Mesozoic, all groups of reptiles formed. The last group - snakes - formed during the Cretaceous period.

At the end of the Cretaceous period, there was a sharp decline in the number of reptile species. Unambiguously indicate the causes of extinction modern science can't yet.

Classification

There is a lot of uncertainty in the classification of reptiles, largely because most of them are extinct. Below is one of the possible options.

• Subclass Anapsida ( Anapsida)
  • Turtles ( Testudines or Chelonia)
  • †Cotylosaurus ( Cotylosauria)
  • †Seymuriomorpha ( Seymouriomorpha)
• Subclass Proganosaurus ( Proganosauria)
  • † Mesosaurs ( Mesosauria)
• Subclass Ichthyopterygia ( Ichtyopterygia)
  • †Ichthyosaurs ( Ichthyosauria)
• Subclass Synaptosaurus ( Synaptosauria or Euryapsida)
  • †Protorosaurus ( Protorosauria)
  • †Sauropterygia ( Sauropterygia)
• Subclass Lepidosaurs or scaly lizards ( Lepidosauria)
  • †Eosuchia ( Eosuchia)
  • Beakheads or proboscis ( Rhynchocephalia)
  • Scaly ( Squamata): lizards and snakes
• Subclass Archosaurs ( Archosauria)
  • †Thecodonts ( Thecodontia) - became extinct, giving rise to other representatives of this subclass and, possibly, birds
  • Crocodiles ( Crocodylia or Crocodilia)
  • †Pterosaurs or flying lizards ( Pterosauria): pterodactyls, etc.
  • †Saurischian dinosaurs ( Saurichia) - extinct, perhaps gave rise to birds
  • †Ornithischian dinosaurs ( Ornithischia)
• Subclass Animalia, or synapsids, or theromorphs ( Synapsida or Theromorpha) - became extinct, but gave rise to mammals.
  • † Pelycosaurus ( Pelycosauria)
  • †Therapsids ( Therapsida)

Reptiles- typical terrestrial animals and their main method of movement is crawling, reptiles on the ground. Key Features The structures and biology of reptiles helped their ancestors leave the water and spread widely across the land. These features primarily include internal fertilization And egg laying, rich in nutrients and covered with a dense protective shell, which facilitates their development on land.

The body of reptiles has protective formations in the form scales, covering them with a continuous cover. The skin is always dry, evaporation through it is impossible, so they can live in dry places. Reptiles breathe exclusively with the help of their lungs, which, compared to the lungs of amphibians, have a more complex structure. Intensive lung breathing became possible thanks to the appearance of a new skeletal section in reptiles - chest. The chest is formed by a number of ribs connected on the dorsal side to the spine, and on the abdominal side to the sternum. The ribs, thanks to special muscles, are mobile and contribute to the expansion of the chest and lungs during inhalation and their collapse at the moment of exhalation.

With a change in structure respiratory system changes in blood circulation are closely related. Most reptiles have a three-chambered heart and two circuits of blood circulation (as do amphibians). However, the structure of the reptile heart is more complex. In its ventricle there is a septum, which at the moment of contraction of the heart almost completely divides it into the right (venous) and left (arterial) halves.

This structure of the heart and the location of the main vessels, different from that of amphibians, more strongly delineates the venous and arterial flows, therefore, the body of reptiles is supplied with blood that is more saturated with oxygen. The main vessels of the systemic and pulmonary circulation are typical of all terrestrial vertebrates. The main difference between the pulmonary circulation of amphibians and reptiles is that in reptiles the cutaneous arteries and veins have disappeared and the pulmonary circulation includes only pulmonary vessels.

About 8,000 currently existing species of reptiles are known, living on all continents except Antarctica. Modern reptiles are divided into orders: protolizards, scaly, crocodiles And turtles.

Reproduction of reptiles

Fertilization in terrestrial reptiles internal: the male injects sperm into the female’s cloaca; they penetrate the egg cells, where fertilization occurs. The female's body develops eggs, which she lays on land (buries in a hole). The outside of the egg is covered with a dense shell. The egg contains a reserve nutrients, due to which the development of the embryo occurs. The eggs do not produce larvae, as in fish and amphibians, but individuals capable of independent life.

First Lizard Squad

TO proto-lizards refers to "living fossil" - tuateria- the only species that has survived to this day only on small islands near New Zealand. This is a sedentary animal, leading a predominantly nocturnal lifestyle and appearance lizard-like. Hatteria in its structure has features that are similar to reptiles and amphibians: the vertebral bodies are biconcave, with a chord preserved between them.

Otrad scaly

Typical representative scaly - quick lizard. Its appearance indicates that it is a terrestrial animal: the five-fingered limbs do not have swimming membranes, the fingers are armed with claws; the legs are short, and therefore the body, when moving, seems to crawl along the ground, every now and then coming into contact with it - reptiles (hence the name).

Lizards

Although the lizard's legs are short, it can run quickly, quickly escaping from its pursuers into its burrow or climbing a tree. This was the reason for its name - quick. The lizard's head is connected to the cylindrical body using the neck. The neck is poorly developed, but will still give the lizard's head some mobility. Unlike a frog, a lizard can turn its head without turning its whole body. Like all land animals, it has through nostrils, and its eyes have eyelids.

Behind each eye, in a small depression, is the eardrum, connected to the middle and inner ear. From time to time, the lizard sticks out of its mouth a long, thin tongue forked at the end - an organ of touch and taste.

The lizard's body, covered with scales, rests on two pairs of legs. The humerus and femur bones are parallel to the surface of the earth, causing the body to sag and drag along the ground. The ribs are attached to the thoracic vertebrae, forming chest, protecting the heart and lungs from damage.

The digestive, excretory and nervous systems of the lizard are basically similar to the corresponding systems of amphibians.

Respiratory organs - lungs. Their walls have a cellular structure, which significantly increases their surface area. The lizard does not have skin respiration.

The lizard's brain is better developed than that of amphibians. Although it has the same five sections, the forebrain hemispheres are larger in size, and the cerebellum and medulla oblongata are much more massive.

The sand lizard is distributed very widely from the Black Sea to the Arkhangelsk region, from Baltic Sea to Transbaikalia. In the north, it gives way to a viviparous lizard similar to it, but more adapted to the cold climate. In the southern regions there are many different types lizards Lizards live in burrows, which in summer weather they leave in the morning and evening, but no further than 10-20 m from the burrow.

They feed on insects, slugs, and in the south - locusts, caterpillars of butterflies and beetles. Within a day, one lizard can destroy up to 70 insects and plant pests. Therefore, lizards deserve protection as very useful animals.

The lizard's body temperature is not constant (the animal is active only in the warm season); it drops sharply even if a cloud approaches the sun. With a longer drop in temperature, the lizard loses mobility and stops eating. During the winter it hibernates; can tolerate freezing and cooling of the body down to -5°, -7°C, while all the life processes of the animal slow down significantly. Gradual warming returns the lizard to active life.

In addition to the sand lizard and viviparous lizard, there are many other species of lizards. Common in Ukraine and the Caucasus large green lizard: in desert areas - agama lizards with a long flexible and unbreakable tail.

Predatory lizard gray monitor lizard, living in the deserts of Central Asia. Its length is up to 60 cm. The monitor lizard eats arthropods, rodents, eggs of turtles and birds. The largest specimens of monitor lizards discovered by herpetologists (the science that studies reptiles) on the island of Komolo reach 36 cm. In the northern regions, the legless lizard is common - spindle.

Chameleons

Chameleons in appearance they resemble medium-sized lizards, with a helmet-shaped outgrowth on the head and a laterally compressed body. This is a highly specialized animal, adapted to an arboreal lifestyle. His fingers are fused together like pincers, with which he tightly grasps the branches of trees. The long and prehensile tail is also used for climbing. The chameleon has a very unique eye structure. The movements of the left and right eyes are not coordinated and independent of each other, which provides some advantages when catching insects. Interesting feature Chameleon's ability to change skin color is a protective device. Chameleons are common in India, Madagascar, Africa, Asia Minor and southern Spain.

Snakes

In addition to lizards, the order Squamate includes snakes. Unlike chameleons, snakes are adapted to crawling on their stomachs and swimming. Due to wave-like movements, the legs gradually completely lost their role as organs of locomotion; only some snakes retained their rudiments (a boa constrictor). Snakes move by bending their legless body. Adaptation to crawling was manifested in the structure internal organs snakes, some of them completely disappeared. Snakes don't have Bladder and just one lung.

Snakes see poorly. Their eyelids are fused, transparent and cover their eyes like a watch glass.

Among the snakes there are non-venomous and poisonous species. The largest non-venomous snake is boa- lives in the tropics. There are boas up to 10 m long. They attack birds and mammals, strangling their prey by squeezing it with their body, and then swallowing it whole. Large boa constrictors that live in tropical forests are also dangerous to humans.

Widespread of non-venomous snakes snakes. The common snake is easily distinguished from poisonous snakes by two orange crescent spots on the head and round pupils of the eyes. It lives near rivers, lakes, ponds, feeding on frogs, and sometimes small fish, swallowing them alive.

Poisonous snakes include viper, cobra, or spectacled snake, rattlesnake and etc.

Viper easily recognized by the long zigzag dark stripe running along the back. IN upper jaw The viper has two poisonous teeth with tubules inside. Through these tubules, the poisonous liquid secreted by the victim enters the wound. salivary glands snakes, and the prey, such as a mouse or small bird, dies.

By destroying huge numbers of mice and locusts, vipers benefit humans. However, their bites can cause long-term illness and even death in animals and even humans. The venom of such snakes as asian cobra, American rattlesnake.

Wounds formed when a person is bitten by a snake look like two red dots. Painful swelling quickly occurs around them, gradually spreading throughout the body. A person develops drowsiness, cold sweats, nausea, delirium, and in severe cases, death occurs.

If a person is bitten by a poisonous snake, it is necessary to immediately take first aid measures., remove excess poison near the wound with blotting paper, cotton wool or a clean cloth, if possible, disinfect the bite site with a manganese solution, strictly protect the wound from contamination, give the victim strong tea or coffee, and ensure rest. Then take him to the hospital as quickly as possible for immediate administration of anti-snake serum. Where there are poisonous snakes, you should not walk barefoot. Care must be taken when picking berries, protecting your hands from snake bites.

Otrad crocodiles

Crocodiles- these are the largest and most highly organized predatory reptiles, adapted to an aquatic lifestyle, living in tropical countries. Nile crocodile Spends most of its life in water, where it swims beautifully, using a strong, laterally compressed tail, as well as hind limbs that have swimming membranes. The crocodile's eyes and nostrils are elevated, so it only needs to raise its head out of the water a little and it can already see what is happening above the water, and also breathe atmospheric air.

On land, crocodiles are slow to maneuver and, when in danger, rush into the water. They quickly drag their prey into the water. These are various animals that the crocodile lies in wait at watering places. It can also attack humans. Crocodiles hunt mainly at night. During the day they often lie motionless in groups on the shallows.

Turtle squad

Turtles differ from other reptiles in their well-developed, durable shell. It is formed from bone plates, covered on the outside with horny substance, and consists of two shields: the upper convex and the lower flat. These shields are connected to each other from the sides, and there are large gaps in front and behind the joints. The head and forelimbs are exposed from the front, and the hind limbs from the back. Almost all aquatic turtles- predators, land animals - herbivores.

Turtles typically lay hard-shelled eggs on land. Turtles grow slowly, but are among the long-livers (up to 150 years). There are giant turtles (soup turtle up to 1 m long. Weight - 450 kg. marsh turtle- up to 2 m and up to 400 kg). They are objects of fishing.

Meat, fat, eggs are used for food, and a variety of horn products are made from the shell. We have one species of turtles - marsh turtle, lives up to 30 years. During the winter it hibernates.