The diversity of amphibians, their significance in nature and for humans, the characteristics of these animals - you will learn about all this by reading the article. Amphibians are otherwise called amphibians. They evolved from fish-like ancestors in the Upper Devonian, about 350 million years ago. At that time, the vast swamps, covered with ferns along the banks, were deserted and were ideal habitats for their development by the first land animals that did not yet know how to retain moisture in their bodies.

The first amphibians

The modern diversity of amphibians did not appear all at once. Unfortunately, there are no photos of ancient animals. They must have looked quite impressive. Paleontological material shows that the first amphibians resembled them with an elongated head and a well-developed tail. These animals, reaching more than 1 m in length, moved slowly and clumsily, crawling with difficulty from one body of water to another. In the Carboniferous, a fairly large variety of amphibians is already found. But they all led a sedentary lifestyle, experiencing almost no competition from other animals, since there was plenty of food.

Difficulties of adaptation

The current diversity and importance of amphibians has developed over a long period of evolution. The transition from an aquatic to a terrestrial existence created many problems for these animals. It took amphibians millions of years to develop the necessary adaptations. In essence, the entire diversity of amphibians is characterized by the fact that these animals have not been able to fully adapt to the more severe conditions of terrestrial habitat and still require an aquatic environment for reproduction. For better movement, amphibians have developed lightweight skeletons and powerful muscles to overcome gravity. The limbs of the first amphibians were short, massive and widely spaced, although they were already five-fingered. For breathing, amphibians used paired air sacs, or lungs.

Modern amphibians

Of the many groups of amphibians that once existed, only three orders have survived: Anura (frogs and toads), Urodela (newts and salamanders) and Apoda (caecilians - elongated, blind burrowing forms). There are over 2500 species of frogs and toads. The variety of amphibians belonging to Anura has adapted to life not only near bodies of water, but also in tropical forests, steppes and even deserts.

Characteristics of frogs and toads

A common feature of all frogs and toads is development with complete transformation (metamorphosis). All of them have a vocal apparatus, but it reaches full development only in males, who emit screams to attract females during the mating season or when frightened. The characteristic croaking sounds are produced by vibrations of the vocal cords - paired folds of the laryngeal mucosa. Air passes past them into the lungs when you inhale and back from the lungs to the voice sacs located under the oral cavity. Almost all frogs and toads in the temperate zone head to water in the spring. They choose the desired direction, guided by special receptive cells - osmoreceptors located in the oral cavity. For unknown reasons, only a few bodies of water are attractive to amphibians, and a great many frogs and toads gather in them during the breeding season. Males usually arrive first and call females with mating calls.

Amphibian skin

As larvae, newts and salamanders breathe in water using external gills that disappear during metamorphosis. Adult frogs can breathe in three ways. At a high level of activity, they carry out this process with the lungs and oral cavity, and during hibernation - with the surface of the skin. In the air, the skin's moisture is maintained by the secretions of the mucus glands. Venom glands are also located in the skin, especially well developed in tropical frogs from the genera Dendrobates and Phyllobates. South American Indians smeared their potent poison on arrows with which they hunted birds and monkeys.

Many venomous amphibians are brightly colored, which serves as a warning to predators. Camouflage coloration is also widespread among amphibians. Pigment cells (3 types) located in the skin, thickening or dispersing pigment, cause color changes.

Newts and salamanders

Newts and salamanders (one of them is shown in the photo above) deviated less from the original type of amphibian structure. The body shape of tailed amphibians resembles lizards. They have a clearly defined head. Adult animals and larvae are very similar to each other, and complete metamorphosis, characteristic of frogs and toads, does not occur in tailed amphibians. There are 8 known families of caudates with approximately 225 species. Like frogs and toads, they usually breed in water. Fertilization in these animals is internal. The male releases a spermatophore, which the female captures with the cloaca. Most tailed fish lay eggs.

Mating behavior of newts and salamanders

During the breeding season, male newts acquire bright colors, which play an important role in their vigorous courtship. Some salamanders are characterized by neoteny - when mature individuals retain the typical features of the larval organization: external gills, transparent, slightly pigmented skin, etc. As a result of pedogenesis, the animal becomes sexually mature at the larval stage. An example of this kind is the axolotl (larva of Ambystoma mexicanum) shown in the photo above.

Worms

Caecilians are the smallest and least studied group of amphibians. Many of them lead a burrowing lifestyle. These animals have no limbs. An interesting primitive feature of caecilians is the retention of scales in the skin. The eyes are greatly reduced, and their function is partly replaced by special tactile tentacles, with the help of which animals correct movement underground. The Ceylon fish snake (Ichthyophis glutinosus), first described at the end of the 19th century, is best known. His photo is presented above.

The South American caecilian is a typical representative. It is blind, lives underground and probably feeds on worms. This species is distributed only in subtropical and tropical areas. The South American caecilian incubates its clutch. The animal reaches 50 cm in length.

So, we have briefly described the diversity of amphibians. The role of amphibians in nature and human life is another interesting topic. We invite you to read about why these animals are so important.

The meaning of amphibians

To one degree or another, all the diversity of amphibians is useful for humans. Their importance is very great, mainly because they feed on many types of harmful invertebrates (insects and their larvae, including mosquitoes; mollusks, etc.). These and other invertebrates damage forests and agricultural crops. In addition, they can be carriers of diseases in pets or humans.

Continuing to describe the diversity and importance of amphibians, we note that the food items of terrestrial amphibians are usually more diverse than those of those with a lifestyle. On average, a grass frog eats 6 invertebrates per day that are harmful to humans. If the number of these amphibians is 100 individuals per 1 hectare, they can destroy more than 100 thousand pests during the summer activity period. Amphibians often eat invertebrates that have an unpleasant taste or odor. Amphibians hunt at night and at dusk. Their useful activity, however, is generally small, since only in a few places do they reach sufficient numbers. Tadpoles, eggs and adult representatives of amphibians leading a mainly aquatic lifestyle are food for many commercial fish, herons, ducks, and other birds. Amphibians, in addition, make up a significant part of the diet of a number of fur-bearing animals (ferret, mink, etc.) in the summer. And otters eat frogs even in winter.

In some regions (America, Southeast Asia, Italy, France), some amphibians (frogs, salamanders) are used by people for food. In the United States, for example, there are farms where bullfrogs are bred (photo above). Only the hind limbs go on sale, and the carcasses are used to feed livestock. At one time, green frogs were also hunted in Ukraine. They were bred for export in the floodplains and estuaries of the Danube. However, their numbers quickly decreased, and their production was stopped.

In temperate latitudes, the number of amphibians is small, so it is necessary to protect them. The diversity of amphibians and their protection is the key to ecological balance.

Order Tailless amphibians

As the name indicates, it unites amphibians that lack a tail in adulthood and have hopping hind legs. There are about 3,500 species known in the world. Frogs, toads and tree frogs live in our country.

Figure: Diversity of amphibians - common frog, pond frog, common tree frog, common toad, crested newt

frogs

Brown frogs- grassy and sharp-faced - appear very early in the spring, as soon as the snow melts, and differ from green ones not only in their brown coloring, but also in their quiet rumbling. Green frogs- pond and lake - in the spring they awaken later than brown ones, when the ice on ponds, lakes and creeks melts, and announce themselves with the loud croaking of males.

Toads

Toads are easily distinguished from frogs by their rough skin covered with tubercles. The skin of toads secretes a caustic liquid that causes irritation if it gets into the eyes or mouth. If this happens, rinse them immediately with clean, cold water. Stories that the skin secretions of toads cause the appearance of warts in humans are without any basis.

Toads are active in the dark, and during the day they hide in various shelters. The hind limbs of toads are shorter than those of a frog. Due to this, toads jump worse.

Thanks to well-developed lungs and dry skin, toads can live away from bodies of water and only go into the water during the breeding season. They settle in vegetable gardens, fields, forests, parks and bring great benefits to humans by exterminating various pests of cultivated plants.

Tree frogs

In our country, in the southern regions of the European part, in the Caucasus and the Far East, there are small frogs 4-5 cm long - tree frogs. It is almost impossible to see them, since they live... in trees. But they scream very loudly. They come down in the spring for spawning and in the fall for wintering.

Order Tailed amphibians

The order Tailed Amphibians unites amphibians with a long tail and short legs. They move with the help of their legs, wave-like movements of the body and tail. About 350 species of tailed amphibians are known. Of these, the most famous are newts.

In the spring, newts develop a wavy crest along their backs, which serves to increase skin respiration. It is especially high in males. In summer, newts come to land and lead a secretive lifestyle near various bodies of water (in old stumps, holes and other wet shelters). During the period of terrestrial life, the newt's crest is not developed.

Salamanders live in the forests of the Carpathian Mountains and the Caucasus. Their skin secretions are poisonous. The color of the common salamander is warning - black, with bright yellow spots.

Importance and protection of amphibians

Amphibians play a large role in nature, entering food chains, and most of them are beneficial to humans. They eat many different plant pests. Toads are especially useful, as they often settle in vegetable gardens and here they exterminate naked slugs. Green frogs destroy many larvae and pupae of blood-sucking mosquitoes. Frogs are of great importance as laboratory animals: various experiments in biology and medicine are carried out on them.

Figure: Rare and endangered species of amphibians - Alpine newt, reed toad, Carpathian newt

All amphibians should not only be protected in every possible way. It is impossible to pollute various small bodies of water, because amphibians can breed in them. Many countries have issued special laws prohibiting their extermination. Sometimes even special measures are taken to protect them from death. Thus, in some countries with heavy traffic, special tunnels are installed under roads through which frogs can move, changing their habitats.

General characteristics of amphibians

Amphibians are cold-blooded animals adapted to life in land-air and aquatic environments. Like all terrestrial vertebrates, they have paired limbs and lungs. Adults have a three-chambered heart and have two circulations. The organs of vision and hearing are adapted to function in the air. The aquatic features of amphibians are manifested in the fact that they lay eggs and develop larvae in water. In adults, bare mucous skin is involved in breathing. Therefore, amphibians stick to wet habitats.

>>Diversity of amphibians, their importance, protection and general features

§ 48. Diversity of amphibians, their importance, protection and general features

The order Tailless Amphibians, as the name indicates, includes amphibians that lack a tail as adults and have hopping hind legs. About 3,500 species are known in the world, 23 species in the USSR. In our country they live frogs, toads and tree frogs 93 .

Frogs living in the USSR are brown and green. Brown ones - grass and sharp-faced - appear very early in the spring, as soon as the snow melts, and differ from green ones not only in their brown coloring, but also in their quiet rumbling. Greens frogs- pond and lake - in the spring they awaken later than brown ones, when the ice on ponds, lakes and creeks melts, and announce themselves with the loud croaking of males.

(!) are easily distinguished from frogs by their rough skin covered with tubercles. The skin of toads secretes a caustic liquid that causes irritation if it gets into the eyes or mouth. If this happens, rinse them immediately with clean, cold water.

Stories that the skin secretions of toads cause the appearance of warts in humans are without any basis.

Toads are active in the dark, and during the day they hide in various shelters. The hind limbs of toads are shorter than those of a frog. Due to this, toads jump worse.

Thanks to well-developed lungs and dry skin, toads can live away from bodies of water and only go into the water during the breeding season. They settle in vegetable gardens, fields, forests, parks and bring great benefits to humans by exterminating various pests of cultivated plants.

Tree frogs.

In our country, in the southern regions of the European part, in the Caucasus and the Far East, there are small frogs 4-5 cm long - tree frogs. It is almost impossible to see them, since they live... in trees. But they scream very loudly. Come down in the spring for spawning and in the fall - for wintering.

The order Tailed Amphibians unites amphibians with a long tail and short legs. They move with the help of their legs, wave-like movements of the body and tail. About 350 species of tailed amphibians are known, in the USSR there are 11 species.

Of these, the best known are newts. 93 .

In the spring, newts develop a wavy crest along their backs, which serves to increase skin respiration. It is especially high in males. In summer, newts come to land and lead a secretive lifestyle near various bodies of water (in old stumps, holes and other wet shelters). During the period of terrestrial life, the newt's crest is not developed.

Salamanders live in the forests of the Carpathian Mountains and the Caucasus (!). Their skin secretions are poisonous. The color of the common salamander is warning - black, with bright yellow spots.

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Class amphibians- these are cold-blooded animals associated with both aquatic and terrestrial environments; there are about 5000 species. They are also called amphibians.

The structure of the amphibian class

Amphibian organ	What parts does it consist of?
SKELETON
Head skeleton	Skull box; Jaws - upper and lower	Brain protection Capturing food
Spine	Vertebrae (there is a cervical vertebra); tail bone	Body support, protection of internal organs
Forelimb belt	Sternum, two crow bones, two collarbones and two shoulder blades	They connect the limbs with the spine
Hind limb belt	Fused pelvic bones attached to the spine	Hind leg support
Forelimb	Humerus, two fused bones of the forearm, small bones of the hand, bones of the four fingers	Support while moving
Hind limb	Femur, two fused bones of the lower leg, bones of the foot and five toes	Push-off while moving
NERVOUS SYSTEM
Brain	Divisions: anterior (better developed than in fish), middle, intermediate, oblongata, cerebellum (due to the uniformity of motor reactions, less developed than in fish)	Movement control, unconditioned and conditioned reflexes
Spinal cord		implementation of simple reflexes, conduction of nerve impulses
	perception and conduction of signals
Sense organs	The organ of vision is the eyes, protected by eyelids; The organ of hearing is the ear (consists of the middle and inner ear, the organs of smell and balance are located in the brain	Perception of signals from the external environment
ORGANS OF THE BODY CAVITY
Digestive system	1. Digestive tract (mouth, pharynx, esophagus, stomach, intestines, anus) 2. Digestive glands (pancreas, liver)	1. Capturing, chopping, moving food 2. secretion of juices that promote food digestion
Respiratory system (may be pulmonary and cutaneous respiration)	Lungs (sacs with elastic walls in which many capillaries branch)	Gas exchange
Circulatory system	Three-chambered heart (two atria and one ventricle), arteries, veins, capillaries; two circles of blood circulation	Supplying all body cells with oxygen and nutrients, removing waste products

Origin of the class Amphibians

Amphibians or amphibians appeared about 375 million years ago. The first amphibians descended from ancient lobe-finned fish, which were of enormous size, which in turn also reached gigantic sizes.

Classification of Amphibians

Amphibians are divided into 3 main orders:

	Representatives	Features and numbers
Squad Tailed	representatives are newts, salamanders, ambistoms, sirens	They all have an elongated body that extends into a tail, and their limbs are short and weak. A feature of tailed animals is the high regeneration of body parts, which happens when animals restore up to the half of their body. This order includes approximately 500 species of amphibians.
Tailless Squad	toads, frogs, toads, tree frogs and others	Representatives of this order have well-developed hind limbs for jumping movement and lack a tail. Includes approximately 4,000 species of amphibians
Legless Squad	these include worms	Primitive amphibians, which have neither tails nor limbs, resemble earthworms.

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A source of information: Biology in tables and diagrams./ Edition 2, - St. Petersburg: 2004.

Amphibian diversity

The first amphibians arose from ancient whale-finned fish, in Devonian Paleozoic era (about 300 million years ago). Ancient Paleozoic amphibians were called stegocephali, or shell-headed amphibians. In the Jurassic and Cretaceous periods of the Mesozoic, typical amphibians appear. Amphibians thrive in the Carboniferous with its warm and humid climate.

Tailed- a number of amphibians with an elongated body, in which the tail section and, predominantly, identical limbs are well defined. There are about 350 species in which fertilization is internal. Distributed mainly in the northern hemisphere. Neoteny is observed in some representatives of the series. Belong to the series salamanders (beach-

Mista, huge, bezlegenevi) , newts (common, comb, Carpathian, alpine) , proteas, sirens, ambistomas and etc.

Anurans- a number of amphibians with a short body, in which the tail is not expressed, the hind limbs are much better developed than the front ones, and often have swimming membranes between the toes. There are about 3,500 species in which fertilization is external. The tail in larvae (tadpoles) is reduced in adults. The remaining caudal vertebrae fused into a rod-shaped bone (urostyle). Tailless amphibians have a number of anatomical features: a limited number of vertebrae (usually 9), elongated bones, etc. There is a tympanic cavity and an eardrum. Tailless amphibians are widespread in all landscape-geographical zones, except for the polar regions (the grass frog also goes beyond the Arctic Circle) and arid deserts. More anurans in tropical America. Some include frogs (sharp-faced, lake, grass, Goliath) , toads (green, of course, reed) , tree frogs, toaded firebirds (zhovtocherevna, chervonocherevna) and etc.

Legless- a series of amphibians with a worm-shaped body elongated with ring-shaped interceptions, which is devoid of limbs and tail. There are about 170 species in which fertilization is internal. Distributed mainly in South America, tropical Africa and South Asia. Most lead an underground lifestyle, digging tunnels in moist soil and plant litter. The eggs develop outside of water, only the last stage of the larva is associated with the aquatic environment. Belong to the series caecilian ringed, ribosemium ceylon and etc.

The importance of amphibians in nature and human life

The meaning of amphibians is varied and important. It lies in the fact that amphibians eat many harmful invertebrates (mollusks, insects and their larvae), mice and rats - carriers of human pathogens. The benefit of amphibians is also great because land representatives are active at night, when other consumers of pests are not hunting. Amphibians themselves are food for many birds and mammals. In some countries, the population eats the meat of frogs and salamanders (for example, the giant salamander, the sharp-faced frog). Frogs and newts are objects of biomedical research. Frogs are widely used in all laboratories around the world. Grateful researchers erected monuments to them in Paris and Tokyo. Amphibians are a source of poisons (bufotoxin from toads, salamandertoxin from salamanders), which are used to obtain medicines. Amphibians also cause some harm: they carry dangerous diseases (tularemia) and eat fish fry. Amphibians play a significant role in nature and human life, and therefore deserve protection. To Krasno? The book of Ukraine lists 5 species of amphibians: Carpathian newt, mountain newt, spotted salamander, reed toad, quick frog.