What distinguishes amphibians from reptiles 15 differences. Amphibians and reptiles. Separately, it is worth highlighting snakes

The Reptile class (reptiles) includes about 9,000 living species, which are divided into four orders: Scaly, Crocodiles, Turtles, Beak-headed. The latter is represented by only one relict species - hatteria. Scaly ones include lizards (including chameleons) and snakes.

  The fast-moving lizard is often found in central Russia

  General characteristics of reptiles

Reptiles are considered the first true terrestrial animals, since they are not related in their development to the aquatic environment. If they live in water (aquatic turtles, crocodiles), then they breathe lightly and go on land for reproduction.

Reptiles settled overland much more than amphibians occupy more diverse ecological niches. However, due to cold-bloodedness, they prevail in a warm climate. In this case, they can live in arid places.

Reptiles appeared 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 all.

The heyday of reptiles came in the Mesozoic era. At this time, various dinosaurs lived on Earth. Among them were not only land and water species, but also flying ones. Dinosaurs became extinct at the end of the Cretaceous.

Unlike amphibians in reptiles

mobility of the head is improved due to a larger 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, venous and arterial blood flows are better separated than amphibians;

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

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

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

germinal membranes (amnion and allantois) appear.

  Reptile skin

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

Reptile scales are not homologous to fish scales. Horny scales are formed by the epidermis, i.e., has an ectodermal origin. In fish, scales are formed by dermis, i.e., have a mesodermal origin.

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

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

Claws appear on the fingers.

Since keratinized skin inhibits growth, then molting is characteristic of reptiles. In this case, the old integuments leave the body.

The skin of reptiles is tightly fused with the body, without forming lymphatic bags, as in amphibians.

  Skeleton of reptiles

Compared with amphibians, in reptiles in the spine there are already not four, but five sections, since the trunk section is divided into the thoracic and lumbar.

In lizards, the cervical spine consists of eight vertebrae (in various species, from 7 to 10). The first cervical vertebra (atlas) looks like a ring. The dentoid 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 greater head mobility. In addition, the first cervical vertebra is connected to the skull with one mouse, and not two like amphibians.

All vertebrae of the thoracic and lumbar spine have ribs. In lizards, the ribs of the first five vertebrae are attached by cartilage to the sternum. A 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 chest is formed. This structure is associated with the features 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 carapace.

The position of the limbs relative to the body is on the sides. In snakes and legless lizards, 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, in many species bifurcated at the end. Reptiles are able to throw it far.

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

The salivary glands contain enzymes.

  Respiratory system of reptiles

Reptiles breathe only lightly, because due to keratinization, the skin cannot take part in breathing.

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

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

The mechanism of inspiration and expiration in reptiles is fundamentally different from that of amphibians. Inhalation occurs when the chest expands due to stretching of the intercostal and abdominal muscles. In this case, air is absorbed into the lungs. When you exhale, the muscles contract and air is expelled from the lungs.

  Circulatory system of reptiles

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

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

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

Three vessels independently depart from the ventricle of a reptile’s heart:

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

Two aortic arcs extend from the left (arterial) part of the ventricle. One aortic arch begins to the left (however called right aortic arch, as it bends to the right) and carries almost pure arterial blood. From the right aortic arch originate the carotid arteries that go to the head, as well as the vessels supplying the belt of the forelimbs with blood. 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 arc is located to the right of the right aortic arch, but is called left aortic arch, since the exit bends to the left. Both aortic arches (right and left) on the dorsal side are connected into a single spinal aorta, the branches of which supply the organs of the body with mixed blood. 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 pelvic ones. Pelvic kidneys have long tubules of nephrons. Their cells are differentiated. In the tubules, there is a reverse absorption of water (up to 95%).

The main excretory product is uric acid. It almost does not dissolve in water, so urine is mushy.

From the kidneys, the ureters flow into the bladder, which opens into the cloaca. In crocodiles and snakes, the bladder is underdeveloped.

  The nervous system and sensory organs of reptiles

The brain of reptiles is improving. In the forebrain appears the cortex of the cerebral hemispheres.

In a number of species, the diencephalon forms the parietal organ (third eye), which is capable of perceiving light.

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

Conditioned reflexes are developed with difficulty. The basis of behavior is instincts (complexes of unconditioned reflexes).

The eyes are supplied with eyelids. There is a third eyelid - a blinking membrane. In snakes, the eyelids are transparent and fused.

A number of snakes at the front end of the head have pits that accept heat radiation. They well determine the difference between the temperatures of surrounding objects.

The hearing organ forms the inner and middle ear.

Well-developed sense of smell. In the oral cavity there is a special organ 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 eggs in the ground. There is a so-called egg-bearing, when the eggs are delayed in the female genital tract, and when they exit, the cubs hatch immediately. Real snakes are observed in sea snakes, while a placenta similar to that of mammals is formed in the embryos.

The 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.

Two embryonic shells are formed in the reptile egg, which are not found 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 serves as the bladder and respiratory organ. The outer wall of the allantois is adjacent to the egg shell and contains capillaries through which gas exchange is carried out.

The care of the offspring of reptiles is rare, it consists mainly in the protection of masonry.

Each person in his life at least once saw frogs or lizards. They can be found near ponds and in shady, humid places. Many mistakenly believe that these two living creatures are relatives and belong to the same biological group. This is absolutely untrue. The characteristic features and distinctive features will help you figure out which class the frog belongs to, amphibian or reptile.

Many people wonder if lizards and frogs belong to the same class, because in some ways they are similar

Class Description Amphibians

Amphibians are very primitive terrestrial animals. The class name displays the main distinguishing feature of the Amphibian class. In the development cycle, they always have a stage of living in water. Adult animals spend most of their time on land, but the reproduction and development of larvae is only possible in water.

Therefore, every spring, frogs lay their eggs in puddles and ponds, where they will subsequently grow in tadpoles. Amphibian skin is covered with mucus and is always wet. This plays a vital role, since respiration in this group of animals occurs to a greater extent through the skin. Only 30% of the absorbed oxygen is in the lungs.

The Amphibian class is divided into 3 groups:

• order Tailless;
• squad tailed;
• legless squad.

By the name of the squad, you can judge which part of the body is lacking in each group. The representative of the Legless is an interesting creature resembling a snake - a worm. Tritons belong to the order Tailed. Well, frogs occupy an honorable place among the tailless amphibians. Toads can also be attributed to them.

  Tritons and salamanders are tailed amphibians, probably all misconceptions due to data from representatives of amphibians

Tadpoles are Amphibian larvae. They are very different from adult animals both externally and internally. Initially, tadpoles lack limbs. They use a tail to move around. The breath is exclusively gill, as they do not go to land. They feed mainly on algae.

With the growth of the tadpole, metamorphoses begin to occur in the body. First, limbs begin to form. First grow back, then front. The tail is saved almost to the very end. Horny teeth appear in the mouth, so the type of food gradually changes from the filter to the predator. The final stage is the formation of the lungs and the appearance of a second type of breathing.

Reptile Class

Reptiles are a large group of terrestrial vertebrates. These include lizards, snakes, and crocodiles. In the Carboniferous period, Reptiles flourished and dominated. On the planet was the heyday of the era of dinosaurs, which are typical representatives of this class.

  Lizards are actually more advanced and are reptiles.

Compared to Amphibians, this is a more progressive group. In their life cycle, there is no connection with water, breathing becomes completely pulmonary. The skin is dry and covered with horny scales. Of the primitive traits, the absence of a constant body temperature remains.

The Reptiles class is divided into the following orders:

• squad Beak-headed;
• squamous squad;
• crocodile squad;
• turtle squad.

There are no questions with representatives of the Crocodile and Turtle units. Lizards and snakes belong to the group of Scaly, and the order Beak-headed has only one representative - hateria.

Comparative characteristics of representatives

Among Amphibians and Reptiles, one can distinguish both a number of common features and features characteristic of only one class. For ease of comparison, these features are tabulated.

Features of the structure of the frog

For life, frogs prefer moist, shady places. They can be found in swamps, near ponds, in forests and along river banks. They are most active in rainy weather or in the evening, when the sun is not so warm as in the afternoon. Drought is an unfavorable condition for the life of frogs.

Various insects, small water mollusks, and sometimes fish fry, serve them as food. Frogs are predators. For hunting, they use their long and sticky tongue. For a long time, the frog can sit motionless and watch the victim, but as soon as the right moment has arrived, it throws its tongue at lightning speed and grabs the prey.

Due to the fact that frogs cannot regulate their body temperature, and it directly depends on the ambient temperature, they lead an active lifestyle in the warm season -   late spring and summer. In winter, they go into hibernation, slowing down all the vital processes in the body.

The frog's body is divided into 2 departments:

• flattened head;
• large oval torso;

There are 2 pairs of limbs. Moreover, the hind limbs are much longer than the front. This feature provides the ability to jump. Frogs mainly breathe moisturized skin, so its drying is deadly for the animal.

Thus, the frog is a typical representative of Amphibians. The features of its structure fully reflect all the distinguishing features of the Amphibian Class.

Toad Description

A toad is a creature that is very similar in appearance to a frog. But upon closer examination, traits characteristic of Reptiles can be distinguished. Therefore, it is rather difficult to determine if a toad is an amphibian or a reptile. It is necessary to consider the similarity of toads with Amphibians and Reptiles.

  Toad has some similarities with reptiles, but if you recall the method of reproduction and the type of breathing, it is immediately clear that this is an amphibian

There are few structural features of the toad, according to which it can be attributed to reptiles. Toads lead a land lifestyle. Their typical habitat is burrows in the soil, cellars, sheds and other similar places. The skin is dry and keratinized.

Structural features of the toad, characteristic of the Amphibian or Amphibian class:

1. Mostly skin respiration. Despite the presence of a horny substance on the surface of the skin, toads breathe and need hydration.
2. Toads breed in ponds. Like frogs, toads spawn in puddles or ponds well lit by the sun. Then tadpoles appear from it.
3. The hind limbs are longer than the front. Move in jumps.

Based on this, there is no doubt that amphibian is a toad or is it a reptile. In this case, some similarities with reptiles are indirect.

At first glance, frogs, toads and lizards are animals that everyone knows very well. Everyone has encountered them in his life. But in order not to say that the frog is a reptile, it is important to study the differences and similarities of these two classes. Get to know the features of their life cycle and habitats. And then it becomes clear that these are very different groups of animals.

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

Crocodile and toad can coexist perfectly in one pond. Therefore, it is likely that it may seem that they are relatives and have common ancestors. But this is a huge mistake. These animals belong to different systematic classes. There are many fundamental differences between them. And they are not only in appearance and size. A crocodile and a lizard are reptiles, and a frog and a 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 ponds. But this is dictated by the fact that they reproduce only in water. Reptiles are not connected with water bodies. On the contrary, they prefer drier and hotter regions.

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

Class Reptiles (reptiles)

The Reptiles, or Reptiles, are terrestrial animals. They got their name thanks to the method of movement. Reptiles do not walk on the ground, they crawl. It was the reptiles that for the first time completely switched from aquatic to land lifestyles. The ancestors of these animals spread widely on the earth. 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 lay eggs that contributed to the development of reptiles outside the reservoir on land.

Reptile structure

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

Reptiles breathe with the help of fairly well-developed lungs. It is also important that intensive breathing in reptiles became possible due to the appearance of a fundamentally new skeleton department. The chest occurs for the first time in reptiles. It is formed by ribs extending from the vertebrae. From the ventral side they are already connected to the sternum. Thanks to the special muscles, the ribs are mobile. This contributes to the expansion of the chest at the time of inspiration.

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

The main large arteries of the small and large circles of blood circulation are fundamentally the same for all groups of terrestrial vertebrates. Of course, there were some minor differences. The skin veins and arteries disappeared in the reptiles. Only the pulmonary vessels remained.

Currently, about 8 thousand species of reptiles are known. They live on all continents, except, of course, Antarctica. Four groups of reptiles are divided: crocodiles, scaly, turtles and first-movers.

Breeding reptiles

Unlike fish and amphibians, reproduction in reptiles is internal. They are dioecious. The male has a special organ with the help of which he introduces sperm into the cloaca of the female. They penetrate the eggs, after which fertilization occurs. Eggs develop in the body of a female. Then she lays them in a 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. Not a larva emerges from an egg, as in fish or amphibians, but individuals capable of independent life. Thus, the reproduction of reptiles fundamentally goes to 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 care about their offspring.

Class Amphibians

Amphibians, or amphibians - these are newts. With rare exceptions, they always live near a reservoir. But there are species that live in the desert, such as the toad-aquifer. During rain, she draws fluid into the subcutaneous sacs. Her body is swelling. Then it burrows in the sand and, secreting a large amount of mucus, experiences a long drought. Currently, about 3400 species of amphibians are known. They are divided into two orders - tailed and tailless. The former include salamanders and newts, while the latter include frogs and toads.

Amphibians are very different from the Reptiles class, for example, the structure of the body and organ systems, as well as the method of reproduction. Like their distant ancestors of fish, they spawn in the water. For this, amphibians often look for puddles separated from the main body of water. Fertilization and the development of larvae occur here. This means that during the breeding season, amphibians have to return to water. This greatly interferes with their resettlement and limits their mobility. Only a few species were 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. Naturally, this caused a number of changes in these animals, not only anatomical, but also physiological. Compared to species remaining in the aquatic environment, amphibians have wider breasts. This contributed to the development and complication of the lungs. Amphibians improved their hearing and vision.

Amphibian habitats

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

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 Reptile 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, and frogs, and 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 the 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. With reptiles, things are different. In the event of drought, they may well make 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, which do not allow moisture to evaporate. The skin of reptiles is devoid of glands secreting mucus, so it is always dry. Their body is protected from drying out, which gives them distinct advantages in a dry climate. For reptiles molting is characteristic. For example, the body of a snake grows all its life. Her skin is wearing out. They inhibit growth, so once a year she "dumps" them. Amphibians have bare skin. It is rich in glands that secrete mucus. But in extreme heat, amphibian can get heat stroke.

Ancestors of reptiles and amphibians

7. Amphibians have four sections of the spine, and reptiles have five. There are similarities 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 themselves are. They are over 300 million years old. They existed in the era of dinosaurs. Crocodiles and the first lizard appeared a little later (see their photo in this article). Snakes are “only” 20 million years old. This is a relatively young species. Although their origin is currently one of the great mysteries of biology.

These are vertebrates, one of the oldest that appeared on Earth in the Devonian period. They evolved from ripidistii, carnivorous predatory fish that emerged from land to land. There are not so many amphibians, about six thousand species, they are divided into tailed, tailless and legless.

In ordinary life, the easiest way to meet a frog or toad. And hardly anyone wanted to run into a giant Chinese salamander, whose weight can reach 100 kg.

Reptiles

Cold-blooded vertebrates. They are at a higher stage of development compared to amphibians. They are divided into four orders: crocodiles (various types of alligators, caimans, crocodiles), turtles, scaly (snakes, chameleons, s) and beak-headed.

The main differences between amphibians and reptiles

1. The appearance of offspring.

Amphibians lay eggs glued together in water or moist burrows. From the tadpoles appear. They have a tail. As they grow older, the tadpoles lose their tail, but acquire for centuries, which gives them the opportunity to see both in water and on land. In reptiles, only a small part refers to viviparous. The rest build nests and lay eggs. The offspring of reptiles is completely independent, since often the parent leaves the clutch and does not return to it. But crocodiles take care of both hatching and hatching.

2. The skin.

The skin of amphibians is smooth, moist. No wonder once they were called naked reptiles. The skin of amphibians is literally penetrated by glands that secrete poisonous mucus to protect against the effects of the external environment and enemies. Some amphibians are harmless and, in order to protect themselves from attack, are forced to imitate the combat color of poisonous frogs and toads. Between the skin and the muscles of the amphibians are cavities with an aqueous liquid.

In reptiles, or scaly reptiles, the skin is practically devoid of glands. It is impervious to liquids and gases. The skin becomes keratinized from above, and scales form on them. Periodically, reptiles molt, shedding skin. Some get rid of the old skin immediately, others in parts. The pattern on the discarded skin is practically invisible, and the skin itself (crawling out) is colorless.

3. The diet.

Amphibians feed on insects, snails, worms, small invertebrate animals, rodents, slugs harmful to plants. They do not disdain caviar laid down by other amphibians and even encroach on their own kind. Sea toads eat dead animals and plants.

Among reptiles, you can find both insectivorous and carnivorous animals. The diet of reptiles includes fish, algae, birds and their eggs, rodents. There are known cases of attacks by a reptile such as a Komodo lizard, even on children. Some of the reptiles are poisonous and, before biting the victim, inject poison into her body.

4. Life expectancy.

Under natural conditions, amphibians cannot boast of longevity. Although in captivity, certain species of salamanders can survive to a half-century anniversary. Life expectancy of snakes and small lizards is from 2 to 20 years. But such reptiles, like turtles, live up to 100-200 years. So reptiles are the elders of the animal world.