Amphibians are ... Signs of amphibians. Respiratory system of amphibians

Almost all of us think that without any special problems we can define any concept from the general school program. For example, amphibians are frogs, turtles, crocodiles and similar representatives of the flora. Yes, it is true. We are able to name some representatives, but what about the description of their characteristics or lifestyle? For some reason they were given a special class? What is the reason? And what is the law? Here with this, you see, it's more difficult.

What will they surprise us with?

It is likely that the respiratory system of amphibians differs from similar internal devices, say, mammals or reptiles. But what? Are there similarities between us and them? We will try to answer all these questions in this article. However, it is worth paying attention to the fact that in the process of studying the material the reader not only learns about what the amphibians are similar to (the turtles and crocodiles to them, by the way, do not apply), but will also get acquainted with the most interesting facts related to the data Animals. We guarantee that you did not even know about something. Why? The point is that the paragraph of the school textbook does not always provide all the necessary range of knowledge.

General information about the class

Class Amphibians (or Amphibians) represents primitive vertebrates, whose ancestors changed the habitat more than 360 million years ago and left the water on land. In translation from the ancient Greek language, the title is translated as "living a double life."

It should be noted that amphibians are cold-blooded creatures with a variable temperature of the body, depending on external conditions of habitation.

In the warm season, they are usually active, but at the onset of colds fall into a hibernation. Amphibians (frogs, newts, salamanders) appear in the water, but the main part of their existence is carried out on land. This feature can be called almost basic in the life of this species of living beings.

Types of amphibians

In general, this class of animals includes more than 3,000 species of amphibians represented by three groups:

• Tailed (salamander);
• Tailless (frogs);
• Legless (worms).

There were amphibians in places with a temperate and hot climate. However, to this day they live there.

Basically they are all small in size and have a length of not more than one meter. The exception is a giant salamander (the main signs of amphibians are as if lubricated), living in Japan and reaching a length of one and a half meters.

Amphibians spend their lives alone. Scientists have determined that this was not the result of evolution. The first amphibians led exactly the same way of life.

Among other things, they are perfectly disguised, changing their color. By the way, not everyone knows that the protection from predators is also served by poison, which is secreted by special cutaneous glands. Perhaps, this feature is unique to reptiles, arthropods and amphibians. Mammals with such a set of characteristic features in nature do not occur. In fact, even difficult to imagine, as, for example, a cat familiar to us could adjust the temperature of its own body depending on changes in the environment or to isolate the poison, defending itself against the attacking dog.

Features of the skin

All amphibians have a smooth, thin layer of skin, rich in cutaneous glands, which secrete mucus, necessary for gas exchange.

The released mucus also protects the skin from drying out and can contain poisonous or signaling substances. Multilayered epidermis is abundantly provided with a network of capillaries. Most of the poisonous individuals can take a bright color, which serves as a protective and preventive device against predators.

In some amphibians of the tailless group, on the upper layer of the epidermis, the formations become cornified. Especially it is developed in toads, in which more than half of the dermal surface is covered with a stratum corneum. It is important to note that the weak keratinization of the cover does not prevent the penetration of water through the skin. Thus the breathing of amphibians is arranged, which are able to breathe under water only by the skin.

In terrestrial species, horny skin can form claws on the limbs. In tailless amphibians, all subcutaneous space is occupied by lymphatic lacunae - the cavity where the water supply accumulates. And only in a few places does the connective tissue of the skin connect with the amphibian musculature.

Lifestyle amphibians

Amphibians, photos of which can be found in all, without exception, textbooks on zoology, undergo several stages of development: those born in water and resembling fish as a result of the transformation acquire pulmonary respiration and the ability to inhabit on land.

Such development does not occur in other vertebrates, but is common in primitive invertebrates.

They occupy an intermediate position between aquatic and terrestrial vertebrates. Inhabitants of amphibians (fish in this plan are more adapted representatives of fauna) in all parts of the world where there is fresh water, except for cold countries. Most of them spend half their lives in the water. In others, adults live on the ground, but in places with high humidity and close to water.

During the drought, amphibians (birds could envy such a feature) fall into suspended animation, buried in mud, and in cold weather in temperate zones are susceptible to hibernation.

The most favorable habitats are tropical countries with moist forests. The least amphibian animals prefer arid zones of nature (Central Asia, Australia, etc.).

These are water-land inhabitants, who usually prefer a nocturnal lifestyle. The day is spent in cover or half asleep. Tailed species move along the earth similarly to reptiles, and tailless species - short jumps.

Amphibians are animals that, as a rule, are able to climb trees. Unlike reptiles, adult males of amphibians are very vociferous, in their youth they are soundless.

Nutrition in most cases depends on the age and stage of development. Larvae eat plant and animal microorganisms. As you grow up, you need a living food. They are already real predators, feeding on worms, insects and small vertebrates. During the heat their appetite rises. The inhabitants of the tropics are much more gluttonous than their relatives from countries with a temperate climate.

At the beginning of life, amphibians, whose photos adorn atlases that clearly demonstrate the evolution of human development, are developing rapidly, but over time their growth slows down considerably. The growth of frogs lasts up to 10 years, although maturity is already reached by 4-5 years. In other species, growth stops only by age 30.

In general, it should be noted that amphibians are very hardy animals, capable of suffering hunger not worse than reptiles. For example, a toad planted in a damp place may be without food for up to two years. The respiratory system of amphibians at the same time continues to function fully.

Also amphibians have the ability to regenerate lost parts of the body. However, in highly organized amphibians such properties are less pronounced or nonexistent.

Like reptiles, amphibians also quickly heal wounds. The tailed species are particularly tenacious. If a salamander or a newt is frozen in water, then they fall into a stupor and become brittle. As soon as the ice melts, the animals return to life again. It is necessary to remove the newt from the water, it instantly contracts and does not show signs of life. Put it back - and the newt immediately comes to life.

The shape of the body and the structure of the skeleton are similar to fish. The brain consists of two hemispheres, a cerebellum and a midbrain and has a simple structure. The spinal cord is more developed than the head. Teeth of amphibians serve only to capture and retain prey, but are not at all suited for chewing. Great importance for the life of amphibians have a respiratory and circulatory system. They, like reptiles, have cold blood.

In appearance and way of life, amphibians (turtles, we recall, do not belong to them, although they sometimes lead a similar way of life) are divided into three groups: tailless, tailed and legless. Representatives of taillesses include frogs, which are distributed throughout the world, where there is moisture and enough food. Frogs like to sit on the beach and bask in the sun. At the slightest risk, they rush into the water and burrow into the mud.

Representatives of such a huge group of animals, like the Amphibians class, swim well. With approach of colds amphibians fall into hibernation. Spawning occurs during the warm season. The development of eggs and tadpoles occurs quickly. Their main food is plant and animal food.

Tailed amphibians are like lizards. They live in water bodies or near water. They lead a nocturnal life, and during the day they hide in shelters. Unlike lizards, on land they are slow and slow, but in the water are very agile. They feed on small fish, mollusks, insects and other small animals. This species includes salamanders, newts, proteas, secretions, etc.

To the detachment of legless amphibians are worms, having an external resemblance to snakes and legless lizards. However, in terms of development and internal structure, they are close to salamanders and proteas. Live worms in tropical countries (except Madagascar and Australia). They live under the ground, laying their way. They lead the same lifestyle as the earthworms that make up their diet. Some worms bring viviparous offspring. Others lay eggs in the soil next to water or in water.

The benefits of amphibians

Amphibians belong to the first and most primitive inhabitants of the land, occupying a special place in the evolution of terrestrial vertebrates, which is the least studied.

For example, the role of birds and mammals in human life has long been known. In this respect, amphibians are very much behind. However, they are also of great importance in the economic activity of man. As is known, in many countries frog legs belong to delicacies and are highly valued. For this purpose, in Europe and North America, about one hundred million frogs are produced annually. This indicates that amphibians also have economic significance.

Adult individuals feed on animal food. Eating harmful insects in gardens, orchards and fields, they benefit the person. Among insects, mollusks or worms there are also carriers of dangerous various diseases.

Amphibians feeding on aquatic microorganisms are considered less useful. Tritons are an exception. And although the basis of their food includes aquatic organisms, they also eat mosquito larvae (including malarial), which multiply in water with warm and standing water.

The benefits of amphibians largely depend on their number, seasonal, fodder and other features. All these factors affect the nutrition of amphibians. For example, a lake frog that inhabits water bodies is more useful than its relatives living in other places.

Unlike birds, amphibians exterminate more insects with repelling and protective functions, which are not eaten by birds. Also, terrestrial species of amphibians feed mainly at night, when many insectivorous birds sleep.

The full value of amphibians in human life can be assessed only if the animals are adequately studied. At present, the biology of amphibians has extremely superficial knowledge.

Amphibians as an important part of the food chain

In some fur-bearing animals, most amphibians are the main food. For example, the survival of a raccoon dog in different habitats directly depends on the number of amphibians in these areas.

Mink, otter, badger and black polecat willingly eat amphibians. Therefore, the number of these animals is significant for hunting grounds. Amphibians are included in the diet and other predators. Especially when there is not enough basic food - small rodents.

In addition, valuable commercial fish in the winter in the reservoirs and rivers eat frogs. Most often their prey is a herbal frog, which, unlike a green frog, is not buried in winter for siltation. In the summer, she eats terrestrial invertebrates, and in winter she goes to winter for a lake. Thus, the amphibian becomes an intermediate link and replenishes the fodder base for fish.

Amphibians and science

Due to its structure and vitality, amphibians began to be used as laboratory animals. It is on the frog that the greatest number of experiments are conducted, beginning with the lessons of biology in the school and ending with large medical research of scientists. For these purposes, more than tens of thousands of frogs are annually used as biological material in laboratories. It is not ruled out that this can lead to the complete extermination of animals. By the way, in England catching frogs is prohibited, and they are now under protection.

It is difficult to list all scientific discoveries related to experiments and physiological experiments on frogs. Recently, their use in laboratory and clinical practice for early diagnosis of pregnancy has been found. The introduction of urine of pregnant women to male frogs and toads causes them a rapid process of spermatogenesis. In this respect, the green toad is especially prominent.

The most unusual amphibian planets

Among the poorly studied species of these animals, there are many rare and unusual specimens.

For example, ghost frogs (genus Heleophryne) - this is in fact the only family of tailless amphibians with only six species, one of which is found only in the cemetery. Apparently, from here also there was such unusual enough name of a kind. They live mainly in the northeast of South Africa near forest streams. They are up to 5 cm in size and camouflage. They lead a nocturnal life, and at night hide under stones. However, to date, two species are almost exterminated.

Proteus (Proteus anguinus) - tail species of the class Amphibians, living in underground lakes. It reaches a length of up to 30 cm. All individuals are blind and have a transparent skin. Hunted proteins are due to the electrical sensitivity of the skin and the sense of smell. They can live without food for up to 10 years.

The next representative, the zooglossus Gardner frog (Sooglossus gardineri) refers to one of the unusual tailless species of the Amphibian family. Is under threat of destruction. Has a length of not more than 11 mm.

Frog Darwin - this is a fairly small tailless species of amphibians, living in cold mountain lakes. Body length about 3 cm. Males nurture their offspring in the throat sac.

Interesting facts about amphibians

• Not all travelers are aware of the fact that there are a lot of cafes in Peru, where special cocktails are prepared from frogs. It is believed that such drinks relieve many diseases, treat asthma and bronchitis, help restore potency. One way of cooking is to grind the live frog in a blender with the addition of bean soup, honey, aloe juice and poppy root. Are you ready to decide and try this food?
• Unusual amphibians live in South America. Paradoxical frogs decrease in size as they grow up. The usual length of an adult reaches only 6 cm. However, their tadpoles grow to 25 cm. A strange feature.
• During the experiments on laboratory frogs, Australian researchers made a random discovery. They found that these animals are able to remove foreign bodies from their body through the bladder. Experienced and very eminent scientists implanted the animals transmitters, which after a while moved to their bladder. Thus, it turned out that getting into the body of amphibians, foreign objects gradually grow soft tissues and are drawn into a bubble. This discovery actually revolutionized the scientific sphere.
• Few ordinary people are aware that the reason for frequent blinking of frogs during meals is pushing food into the throat. Animals are not able to chew food and push it into the esophagus. Blinking, eyes are drawn into the skull by special muscles and help push food.
• A very interesting specimen is the African frog Trichobatrachus robustus, which has an amazing device for protecting from enemies. At the moment of the threat of her paws pierce the subcutaneous bones, forming a kind of "claws". After the danger passes, the "claws" retract, and the damaged tissue regenerates. Agree, not every representative of modern fauna can boast of having such a useful and unique feature.