Reptiles differ from amphibians by their presence. Differences between reptiles and amphibians. Amphibians and reptiles of the Yaroslavl region

Reptiles and amphibians are two classes of vertebrates. Not everyone succeeds in figuring out which of them a particular representative of the fauna belongs to. To correctly navigate the existing classification, you need to know how reptiles differ from amphibians.

general information

Reptiles and amphibians have second names. Reptiles are also called reptiles, and amphibians are amphibians. It was the reptiles that were the largest animals - dinosaurs. Reptiles once dominated everywhere on Earth. Then most of them became extinct. The most famous representatives of modern reptiles are crocodiles, turtles, snakes and lizards.

Reptiles

Now let's say who belongs to the amphibians. This is a frog, newt, salamander. Amphibians are vertebrates of the most primitive structure. These animals have such a name because an important habitat for most of them is land, and the necessary environment for reproduction and development is water. Among the amphibians, there are those that spend their lives mainly in the water.

Comparison

Skin covering

For reptiles, the connection with water is not so important. They often settle in dry and hot areas. Scaly skin protects the body of animals from drying out. In turtles, the shell, which serves as a shelter from faster pursuers, is also accrete scales. Reptiles shed periodically. The skin is shed all at once or in parts. Thanks to this, the scales do not restrain the growth of the animal.

The body of amphibians is not covered with scales. Many people disdain to touch these creatures because of their wet and slippery skin. It's all about the glands that produce mucus, which literally penetrate the skin of animals.

Organ structure

The difference between reptiles and amphibians is that the former have a more perfect physiology. Their nervous system is complicated. Hearing, vision and other senses are well developed. Reptiles are born with already formed lungs, while the larvae of amphibians have gills.

The structure of the spine in amphibians is simpler - it consists of four sections. The spine of reptiles is represented by five sections. In addition, tailless amphibians lack ribs.

Reproduction

Internal fertilization is a predominant feature of all reptiles. Some animals of this class, such as crocodiles, lay eggs. After a while, fully developed individuals hatch from them, differing from their parents only in size. Live birth is inherent in other types of reptiles.

The method of reproduction of amphibians is to throw eggs into the water. From the eggs glued together, larvae soon emerge, which develop into adults only after more than one month.

Life span

What is the difference between reptiles and amphibians, if you compare the duration of the existence of both? It should be noted here that many reptiles, under favorable conditions, live for a very long time - more than a dozen years. There are also centenarians among them, the existence of which can last more than a hundred or even two hundred years. Turtles are such champions.

Amphibians are not fortunate enough to have such a long life. Even a dozen years for most of them is considered an exorbitant value. In captivity, the lifespan of representatives of certain species may increase. This applies, for example, to salamanders.

Each of us, even if only in pictures, has seen frogs and lizards, crocodiles and toads - these animals belong to the classes Amphibians and Reptiles. The example we have given is far from the only one. There are really many such creatures. But here's how to tell who is who? What is the difference between amphibians and reptiles, and how significant are these differences?

Crocodile and toad can get along well in the same body of water. Therefore, it is likely that it may seem as if they are related and have common ancestors. But this is a huge mistake. These animals belong to different taxonomic classes. There are many fundamental differences between them. And they are not only in appearance and size. The crocodile and lizard are reptiles, and the frog and toad are amphibians.

But, of course, amphibians and reptiles have some similarities. They prefer areas with warm climates. True, amphibians choose humid places, preferably near water bodies. But this is dictated by the fact that they reproduce only in water. Reptiles, on the other hand, are not associated with water bodies. On the contrary, they prefer drier and hotter regions.

Let's look at the structure and physiological characteristics of reptiles and amphibians, and compare how they differ from each other.

Class Reptiles (reptiles)

The class Reptiles, or Reptiles, are land animals. They got their name due to the way of movement. Reptiles do not walk on the ground, they crawl. It was the reptiles who for the first time completely switched from aquatic to terrestrial lifestyle. The ancestors of these animals spread widely across the land. An important feature of reptiles is internal fertilization and the ability to lay eggs rich in nutrients. They are protected by a dense shell, which includes calcium. It was the ability to make clutches of eggs that contributed to the development of reptiles outside the reservoir on land.

Reptile structure

The body of reptiles has strong formations - scales. They cover reptile skin tightly. This protects them from moisture loss. Reptile skin is always dry. Evaporation does not occur through it. Therefore, snakes and lizards are able to live in deserts without discomfort.

Reptiles breathe with the help of well-developed lungs. It is important that intensive respiration in reptiles became possible due to the appearance of a fundamentally new section of the skeleton. The rib cage first appears in reptiles. It is formed by ribs extending from the vertebrae. On the ventral side, they are already connected to the sternum. Thanks to the special musculature, the ribs are mobile. This promotes the expansion of the chest during inhalation.

The Reptile class has undergone changes in the circulatory system. This is due to the complication. The vast majority of reptiles, like amphibians, have two circles of blood circulation. However, there are also some differences. For example, there is a septum in the ventricle. When the heart contracts, it practically divides it into two halves (right - venous, left - arterial). The location of the main blood vessels delineates arterial and venous flows more clearly. As a result, the body of reptiles is supplied with oxygen-enriched blood much better. At the same time, they have more established processes of intercellular exchange and the removal of metabolic products and carbon dioxide from the body. There is also an exception in the Reptiles class, for example a crocodile. Its heart is four-chambered.

The main large arteries of the pulmonary and systemic circulation are fundamentally the same for all groups of terrestrial vertebrates. Of course, there were some small differences here too. In reptiles, the skin veins and arteries have disappeared. Only the pulmonary vessels remained.

Currently, about 8 thousand species of reptiles are known. They inhabit all continents, apart from, of course, Antarctica. There are four groups of reptiles: crocodiles, scaly, turtles and primitives.

Reproduction of reptiles

Unlike fish and amphibians, reptiles reproduce internally. They are dioecious. The male has a special organ, with the help of which he injects spermatozoa into the cloaca of the female. They penetrate the eggs, after which fertilization occurs. The eggs develop in the female's body. Then she lays them in a pre-prepared place, as a rule, this is a dug hole. Outside, reptile eggs are covered with a dense calcium shell. They contain the embryo and the supply of nutrients. It is not the larva that emerges from the egg, like in fish or amphibians, but individuals capable of independent life. Thus, the reproduction of reptiles is fundamentally reaching a new level. The embryo undergoes all stages of development in the egg. After hatching, it does not depend on the reservoir and may well survive on its own. As a rule, adults do not show concern for their offspring.

Class Amphibians

Amphibians, or amphibians, are also newts. They, with rare exceptions, always live near the reservoir. But there are species that live in the desert, such as the aquifer toad. When it rains, it collects liquid in the hypodermic sacs. Her body swells. Then it buries itself in the sand and, secreting a large amount of mucus, survives a prolonged drought. Currently, there are about 3400 known species of amphibians. They are divided into two groups - tailed and tailless. The former include salamanders and newts, the latter - frogs and toads.

Amphibians are very different from the Reptiles class, an example is the structure of the body and organ systems, as well as the way of reproduction. Like their distant fish ancestors, they spawn in the water. For this, amphibians often look for puddles, separated from the main body of water. Both fertilization and development of larvae take place here. This means that during the breeding season, amphibians have to return to water. This greatly interferes with their settlement and restricts their movement. Only a few species have been able to adapt to life away from water bodies. They give birth to mature offspring. That is why these animals are called semi-aquatic.

Amphibians are the first of the chordates to develop limbs. Thanks to this, in the distant past, they were able to land on land. This naturally caused a number of changes in these animals, not only anatomical, but also physiological. Compared to species remaining in the aquatic environment, amphibians have a wider chest. This contributed to the development and complication of the lungs. The organs of hearing and sight improved in amphibians.

Habitats of amphibians

Like reptiles, amphibians prefer to live in warm regions. Usually frogs are found in humid places near water bodies. But you can see them both in meadows and in forests, especially after heavy rain. Some species thrive even in deserts. For example, the Australian toad. She has adapted very well to survive the prolonged drought. In such conditions, other species of toads would certainly quickly die. But she learned to store vital moisture in her subcutaneous pockets during the rainy season. In addition, during this period, it reproduces, laying eggs in puddles. For tadpoles one month is enough for complete transformation. The Australian toad, in extreme conditions for its species, not only found a way to reproduce offspring, but also successfully find food for itself.

Differences between reptiles and amphibians

Although at first glance it seems that amphibians are not much different from reptiles, this is far from the case. In reality, there are not so many similarities. Amphibians have less perfect and developed organs than the Reptiles class, for example - amphibian larvae have gills, while the offspring of reptiles are already born with formed lungs. In fairness, it should be noted that newts, frogs, turtles, and even snakes may well coexist on the territory of one reservoir. Therefore, some do not see significant differences in these units, often confused about who is who. But fundamental differences do not allow combining these species into one class. Amphibians always depend on their habitat, that is, a reservoir, in most cases they cannot leave it. This is not the case with reptiles. In the event of a drought, they may well take a short trip and find a more favorable place.

This is possible largely due to the fact that the skin of reptiles is covered with horny scales that do not allow moisture to evaporate. Reptile skin is devoid of mucus secreting glands, so it is always dry. Their bodies are protected from drying out, which gives them distinct advantages in dry climates. Moulting is characteristic of reptiles. For example, a snake's body grows throughout its life. Her skin "wears out". They hold back growth, so once a year she "dumps" them. Amphibians have bare skin. It is rich in mucus secreting glands. But in extreme heat, the amphibian can get heatstroke.

Ancestors of reptiles and amphibians

7. Amphibians have four sections of the spine, while reptiles have five. This has features of similarity between mammals and reptiles.

The largest reptiles that have ever existed on earth are dinosaurs. They disappeared about 65 million years ago. They inhabited both the sea and the land. Some species were able to fly. Currently, the turtles are the most. They are over 300 million years old. They existed in the era of the dinosaurs. A little later, crocodiles and the first lizard appeared (you can see their photos in this article). Snakes are "only" 20 million years old. This is a relatively young species. Although it is their origin that is currently one of the great mysteries of biology.

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 cross-finned fish that lived in fresh, drying up reservoirs.

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 respiration, have fins, a two-chambered heart and one circle of blood circulation. The adult forms are characterized by a three-chambered heart, two circles of blood circulation, two pairs of limbs. 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 in the tropics, where climatic conditions are suitable for them.

These are dioecious animals. They are characterized by external fertilization and development in water. A tailless amphibian, such as a frog, produces a tailed larva - a tadpole with long fins and branched gills. As development progresses, the front limbs appear, then the hind ones, the tail begins to shorten. Branched gills disappear, gill slits (internal gills) appear. Lungs are formed from the anterior part of the digestive tube, as the gills disappear as they develop. Corresponding changes take place in the circulatory, digestive and excretory systems. The tail is absorbed, and the young frog comes out on land. In tailed amphibians, the gills persist much longer (sometimes all their lives), the tail does not dissolve.

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

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

Tailed amphibians the most primitive. They live in water and near water, their limbs, as a rule, are poorly developed. In some, feathery gills persist throughout their lives.

The ambistoma larva - axolotl even begins to reproduce before reaching the adult stage. The most numerous are salamanders.

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

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

Reptiles (reptiles). Reptiles are terrestrial vertebrates. They adapted well to life on land and drove out 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 in amphibians: the cerebral hemispheres are much larger (see Fig. 85). The behavior of reptiles is much more complex than that of amphibians. In addition to congenital unconditioned, conditioned reflexes are also formed in them. The digestive, excretory and circulatory systems open in cloaca- part of the intestine.

The body of reptiles is covered with scales. It forms in the thickness of the skin - the epidermis - and protects the body from drying out. Some species shed scales in the process of 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 membrane. Even among aquatic inhabitants, egg development takes place on land. Live birth is characteristic of some species.

Reptiles reached their greatest flourishing in the Mesozoic era, about 100-200 million years ago, therefore this era is called the era of reptiles. There was 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 became extinct about 70 million years ago. The cause of the extinction is still not fully understood. There are several hypotheses: a sudden sharp climate change, 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 - spectacle snake; 7 - a 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 turtles (up to 110 cm long) are the largest living on land. They are common in the Galopogos Islands of the Pacific Ocean, in Madagascar, and the islands of the Indian Ocean.

Sea turtles are much larger (up to 5 m) and 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. In some (yellow-bellied) limbs are lost, they resemble snakes.

Have the serpent the main feature is a long, limbless body. These are crawling animals. All snakes are predators, they swallow prey whole or strangle, squeezing their bodies in rings. Poisonous glands (modified salivary glands) open with a duct at the base of a 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 living in the water, along the river banks. On land, they move slowly, but they swim beautifully. Females lay eggshell-covered eggs on land in small holes. They are characterized by taking care of the offspring: the female protects the clutch and takes care of the cubs.

Reptiles live mainly in warm climates: tropics, subtropics, in humid 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 in the preparation of 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 nurseries.

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§ 62. Chordates. Fishes§ 64. Birds

The class Reptiles (reptiles) includes about 9000 living species, which are divided into four orders: Scaly, Crocodiles, Turtles, Beakheads. The latter is represented by only one relict species - the tuatara. Scaly species include lizards (including chameleons) and snakes.

General characteristics of reptiles

Reptiles are considered the first true land animals, since they are not associated in their development with the aquatic environment. Even if they live in water (aquatic turtles, crocodiles), they breathe with their lungs and go to land for reproduction.

Reptiles are settled on land much more than amphibians and occupy more diverse ecological niches. However, due to their cold bloodedness, they predominate in warm climates. At the same time, they can live in arid places.

Reptiles emerged from stegocephals (an extinct group of amphibians) at the end of the Carboniferous period of the Paleozoic era. Turtles appeared earlier, and snakes later than everyone else.

The heyday of reptiles fell on the Mesozoic era. During this time, various dinosaurs lived on Earth. Among them were not only terrestrial and aquatic species, but also flying ones. Dinosaurs became extinct at the end of the Cretaceous.

Unlike amphibians, reptiles

improved mobility of the head due to a greater number of cervical vertebrae and a different principle of their connection with the skull;

the skin is covered with horny scales that protect the body from drying out;

breathing is only pulmonary; the chest is formed, which provides a more perfect breathing mechanism;

although the heart remains three-chambered, the venous and arterial blood flows are better separated than in amphibians;

pelvic kidneys appear as excretory organs (and not trunk ones like in amphibians); such kidneys retain water in the body better;

the cerebellum is larger than that of amphibians; increased volume of the forebrain; the rudiment of the cerebral cortex appears;

internal fertilization; reptiles reproduce on land mainly by laying eggs (some viviparous or ovoviviparous);

the embryonic membranes (amnion and allantois) appear.

Reptile skin

The skin of reptiles consists of a multilayer epidermis and a connective tissue dermis. The upper layers of the epidermis are keratinized, forming scales and scutes. The main purpose of scales is to protect the body from water loss. Overall, the skin is thicker than that of amphibians.

Reptile scales are not homologous to fish scales. Horny scales are formed by the epidermis, that is, it has an ectodermal origin. In fish, the scales are formed by the dermis, that is, they have a mesodermal origin.

Unlike amphibians, there are no mucous glands in the skin of reptiles, so their skin is dry. There are only small odorous glands.

In turtles, a bony shell forms on the surface of the body (above and below).

Claws appear on the fingers.

Since keratinized skin inhibits growth, molt is characteristic of reptiles. In this case, the old integument leaves the body.

Reptile skin grows tightly with the body, without forming lymphatic sacs, as in amphibians.

Reptile skeleton

In comparison with amphibians, in reptiles, not four, but five sections are distinguished in the spine, since the trunk section is divided into thoracic and lumbar.

In lizards, the cervical region consists of eight vertebrae (in various species there are from 7 to 10). The first cervical vertebra (atlas) looks like a ring. The odontoid process of the second cervical vertebra (epistrophy) enters it. As a result, the first vertebra can rotate relatively freely around the process of the second vertebra. This gives a lot of head mobility. In addition, the first cervical vertebra is connected to the skull by one mouse, and not two like in amphibians.

All vertebrae of the thoracic and lumbar spine have ribs. In lizards, the ribs of the first five vertebrae are joined by cartilage to the sternum. The chest is formed. The ribs of the posterior thoracic and lumbar vertebrae are not connected to the sternum. However, snakes do not have a sternum and therefore no rib cage is formed. This structure is associated with the peculiarities of their movement.

The sacral spine in reptiles consists of two vertebrae (and not one as in amphibians). The ilia of the pelvic girdle are attached to them.

In turtles, the vertebrae of the body fuse with the dorsal shield of the shell.

The position of the limbs relative to the body is on the sides. In snakes and legless lizards, the limbs are reduced.

Digestive system of reptiles

The digestive system of reptiles is similar to that of amphibians.

In the oral cavity there is a mobile, muscular tongue, which in many species is forked at the end. Reptiles are capable of throwing it far away.

In herbivorous species, a cecum appears. However, most are predators. For example, lizards feed on insects.

The salivary glands contain enzymes.

Respiratory system of reptiles

Reptiles breathe only with the lungs, since due to keratinization, the skin cannot take part in breathing.

The lungs are improved, their walls form numerous partitions. This structure enlarges the inner surface of the lungs. The trachea is long, at the end it divides into two bronchi. In reptiles, the bronchi in the lungs do not branch.

Snakes have only one lung (right, and the left is reduced).

The mechanism of inhalation and exhalation in reptiles is fundamentally different from that in amphibians. Inhalation occurs when the chest expands by stretching the intercostal and abdominal muscles. In this case, air is sucked into the lungs. As you exhale, the muscles contract and air is pushed out of the lungs.

The circulatory system of reptiles

The heart of the vast majority of reptiles remains three-chambered (two atria, one ventricle), and arterial and venous blood is still partially mixed. But in comparison with amphibians, in reptiles, the venous and arterial blood flows are better separated, and, therefore, the blood mixes less. There is an incomplete septum in the ventricle of the heart.

Reptiles (like amphibians and fish) remain cold-blooded animals.

Crocodiles have a complete septum in the ventricle of the heart, and thus two ventricles are formed (its heart becomes four-chambered). However, blood can still mix through the aortic arch.

Three vessels independently depart from the ventricle of the heart of reptiles:

From the right (venous) part of the ventricle departs common trunk of the pulmonary arteries, which is further divided into two pulmonary arteries going to the lungs, where the blood is enriched with oxygen and returns through the pulmonary veins to the left atrium.

Two aortic arches extend from the left (arterial) part of the ventricle. One aortic arch begins to the left (however, it is called right aortic arch, since it bends to the right) and carries almost pure arterial blood. From the right aortic arch originate the carotid arteries leading to the head, as well as the vessels supplying blood to the belt of the forelimbs. Thus, these parts of the body are supplied with almost pure arterial blood.

The second aortic arch departs not so much from the left side of the ventricle as from its middle, where the blood is mixed. This arch is located to the right of the right aortic arch, but is called left aortic arch, as it bends to the left at the exit. Both aortic arches (right and left) on the dorsal side are connected to form a single dorsal aorta, the branches of which supply the organs of the body with mixed blood. The venous blood flowing from the organs of the body enters the right atrium.

Excretory system of reptiles

In reptiles, in the process of embryonic development, the trunk kidneys are replaced by the pelvic kidneys. The pelvic kidneys have long tubules of nephrons. Their cells are differentiated. In the tubules, water is reabsorbed (up to 95%).

The main excretion product of reptiles is uric acid. It is almost insoluble in water, so the urine is mushy.

The ureters depart from the kidneys and drain into the bladder, which opens into the cloaca. In crocodiles and snakes, the bladder is underdeveloped.

The nervous system and sense organs of reptiles

The brain of reptiles is being improved. The cerebral cortex of the gray medulla appears in the forebrain.

In a number of species, the diencephalon forms the parietal organ (third eye), which is able to perceive light.

The cerebellum in reptiles is better developed than in amphibians. This is due to the more varied motor activity of reptiles.

Conditioned reflexes are difficult to develop. The basis of behavior is instincts (complexes of unconditioned reflexes).

The eyes are equipped with eyelids. There is a third eyelid - the nictitating membrane. In snakes, the eyelids are transparent and grow together.

A number of snakes have thermal pits at the front end of their heads. They are good at determining the difference between the temperatures of surrounding objects.

The organ of hearing forms the inner and middle ear.

The sense of smell is well developed. There is a special organ in the oral cavity that distinguishes odors. Therefore, many reptiles stick out a forked tongue at the end, taking air samples.

Reproduction and development of reptiles

All reptiles are characterized by internal fertilization.

Most lay their eggs in the ground. There is the so-called ovoviviparity, when the eggs are retained in the genital tract of the female, and when they leave them, the cubs immediately hatch. In sea snakes, a real live birth is observed, while a placenta is formed in the embryos, similar to the placenta of mammals.

Development is direct, a young animal appears, similar in structure to an adult (but with an underdeveloped reproductive system). This is due to the presence of a large supply of nutrients in the egg yolk.

In the egg of reptiles, two embryonic shells are formed, which are not in the eggs of amphibians. it amnion and allantois... The embryo is surrounded by an amnion filled with amniotic fluid. Allantois is formed as an outgrowth of the posterior end of the intestine of the embryo and performs the functions of the bladder and respiratory organ. The outer wall of the allantois is adjacent to the egg shell and contains capillaries through which gas exchange takes place.

Caring for offspring in reptiles is rare, mainly in the protection of the clutch.