Animals: reproduction and development in most species occurs in aquatic environment, and adults are inhabited by land.

Encyclopedic YouTube.

1 / 5

✪ Amphibian class

✪ amphibians. The difference of amphibians from other animals. Video Tutorial on the world class 1 class

✪ 13.1 Amnere Part I (Grade 7) - biology, preparation for the exam and OGE 2018

✪ Kingdom Animals: amphibian class. Class Presbysey

✪ 13. Amphibian. Part 1

Subtitles

general characteristics

Skin Covers

All amphibians have a smooth thin skin, relatively easily permeable for liquids and gases. The structure of the skin is characteristic of vertebrates: multi-layered epidermis and leather actually (Corim) stands out. The skin is rich in skin glands excreasing mucus. Some mucus can be a poisonous or facilitating gas exchange. The skin is an additional gas exchange organ and is equipped with a thick capillary network.

The horny formations are very rare, also rare and oases of the skin: Ephippiger Aurantiacus. and horned toad species Ceratophrys Dorsata. There is a bone plate in the skin of the back, in the guise of amphibians - scales; The toad sometimes under the old age is deposited lime in the skin.

Skeleton

The body is divided into head, torso, tail (in tailed) and five-plated limbs. The head is movably connected to the torso. The skeleton is divided into departments:

• axial skeleton (spine);
• skeleton head (skull);
• skeleton of paired limbs.

• leather-racing artery (carry venous blood to light and skin);
• sleepy arteries (supply heads with arterial blood);
• the aortic arches carry mixed blood to the other body bodies.

Small circle - light, begins with skin-eye arteries that carry blood to the respiratory organs (light and skin); From the light oxygen-enriched blood is assembled into paired light veins flowing into the left atrium.

A large circle of blood circulation begins arcs of aortic and carotid arteries that are branched in organs and tissues. The venous blood on the steam front hollow veins and the unpaired rear hollow vein falls into the right atrium. In addition, oxidized blood from the skin falls into the front hollow veins, and therefore blood in the right atrium is mixed. In addition to the usual heart, all amphibians have lymphatic hearts that are located in front of the liabilities in the veins of lymphatic vessels.

Due to the fact that body bodies are supplied with mixed blood, amphibians have a low level of metabolism, and therefore they are cold-blooded animals.

Digestive organs

All amphibians are powered by mobile mining. At the bottom of the rotoglota cavity is the language. In adversely, he is attached to the lower jaws, when fishing insects, the yoke is thrown out of the mouth, mining adhesions. On the jaws there are teeth, serving only to hold mining. The frogs are located only on the upper jaw.

In the rotoglotaceous cavity, the ducts of the salivary glands are opened, the secret of which does not contain digestive enzymes. From the rotoglotage cavity food on the esophagus enters the stomach, from there in the duodenum. Liver and pancreas are opening here. Food digestion occurs in the stomach and in the duodenum. The delicious intestine goes into the rectum, which forms the extension - Cloaca.

Options

The brain consists of 5 departments:

• the front brain is relatively large; divided into 2 hemispheres; has large olfactory shares;
• the intermediate brain is well developed;
• the cerebellum is developed weakly due to uncomplicated, monotonous movements;
• the oblong brain is the center of the respiratory, blood and digestive system;
• the middle brain is relatively small, is the center of view, the tone of the skeletal muscles.

10 pairs depart from the brain head nerves (I-x).

Spinal nerves The tales and adults form a well-pronounced shoulder and lumbar plexus. Well developed sympathetic nervous systemrepresented mainly by two nervous trunks located on the sides of the spine.

Sense organs

Taste organs are located in the oral cavity. It is assumed that the frog perceives only bitter and salty.

Sender organs

All amphibian separation. In most amphibian fertilization external (in water).

Amphibians of some species show care of the offspring (toad, quacs).

Lifestyle

Most amphibians conducts life in wet places, alternating staying on land and in water, however there are some purely water species, as well as types of life exclusively on trees. Insufficient adaptation of amphibians for habitat in the ground environment causes sharp changes in their lifestyle due to seasonal changes in the conditions of existence. Amphibians are capable of falling into a long hibernation under adverse conditions (cold, drought, etc.). In some species, activity can vary with the night to the day when the temperature drops at night. Amphibians are active only in warm conditions. At temperatures +7 - +8 ° C, most species fall into a stupor, and at -1 ° C - dying. But some amphibians are able to transfer long-term freezing, drying, as well as regenerate significant lost parts of the body.

Some amphibians, such as sea toad Bufo Marinus.can live in salty water. However, most amphibians are found only in fresh water. Therefore, they are absent on most ocean islands, where conditions for them are in principle favorable, but they can not get to which they independently can.

Food

All modern amphibians in the adult stage are predators, feed on small animals (mostly insects and invertebrates) are prone to cannibalism. There are no vegetative animals among amphibians because of the extremely slugging metabolism. In the diet of water species, young fish can enter, and the largest can be hunted on the chicks of waterfowl and in the water of small rodents.

The nature of the nutrition of the larvae of tailed amphibians is almost similar to the nutrition of adult animals. The larvae of taped have a cardinal difference, feeding by plant food and a daddy, moving to predatoryness only by the end of the larch stage.

Reproduction

The total feature of the reproduction of almost all amphibians is their attachment during this period to water, where they lay eggs and where the development of larvae occurs. Improving amphibians in small, well-heated areas of water bodies. In the warm spring evenings, at the end of April and in May, with ponds, loud piggy sounds are distributed. These "concerts" arrange males frogs to attract females. The breeding bodies in males are the seeds, in females - ovaries. Outdoor fertilization. Caviar is glued to aquatic plants or stones.

Virulence

The most poisonous vertebrate animals on Earth belong to the detachment of elderly amphibians - these are tree frogs. A poison that is released amphibious glands contains killing bacteria substances (bactericides). Most of the majority of Russia has a poison completely harmless to humans. However, many tropical frogs are not so safe.

An absolute "champion" on poisonousness among all vertebrates, including snakes, should recognize a resident of the rainforest of Colombia - tiny, the size of only 2-3 cm, terrible leisure (local residents call it "cookers"). Its skin mucus contains batrahotoxin. From the skin of the cokey, the Indians prepare poison for arrows. One frog is enough to poison 50 arrows. 2 mg of purified poison is enough to kill a person. However, this frog has a natural enemy - a small snake Leimadophis EpinePhelus.powered by young leafolazes.

Amphibians and People: Active Life

Thanks to the survivability, amphibians are often used as laboratory animals.

Classification

The word "amphibian" comes from an ancient Greek term ἀμφίβιος (amphíbios), which means "both kinds of life", ἀμφί means "both species" and βιος means "life". The term was originally used as a general definition for animals that can live on land and in water, including seals and outers. Traditionally, the class of amphibians includes all four-legged vertebrates that are not amnides. Amphibians in the broadest sense (Sensu Lato) were divided into three subclasses, two of which are extinct:

• Subclass of labyrinthodontics († Labyrinthodontia - separate Paleozoic and Ranniersozaic group)
• The subclass of thin-star († lepospondyli is a small Paleozoic group, sometimes turns on in labyrinthodontics, which can actually be more closely related to amniotes than with tanzar)
• Subclass of Bezapambia (Lissamphibia - all modern amphibians, including frogs, toads, salamander, tritons and worm)
  • The detachment of heavy (Anura - Frogs and Zhab): from the Jurassic period to the present - 5,602 current views in 48 families
  • Detachment Tailed amphibians (Caudata or Urodela - Salamandra, Tritons): from the Jurassic period to the present - 571 current views in 10 families
  • Gymnophiona or APODA - Coverage detachment: from the Jurassic period to the present - 190 current views in 10 families

The actual number of species in each group depends on the chosen taxonomic classification. The two most common systems are: classification adopted on the AmphibiaWeb website of the University of California in Berkeley, and the classification of the Herpelologist Darrel Frug and the American Natural History Museum available online as a reference database. The number of species is indicated on frost, and the total number of known types of amphibians is about 7,000, of which about 90% are frogs.

All modern amphibians are included in the subclass of tanctsary, which is usually considered to be a group of species that occurred from the overall ancestor. However, it was suggested that Salamandras arose separately from dyeing-like ancestors, and even that the worms are a nursing group of advanced replicomorphous amphibians, and therefore amniotami.

Although there are several more ancient fossils of proto-frogs, still the ancient "true frog" is considered to be Prosalirus Bitis, found in the Nizhnyaya sediments of Kayenti formation, Arizona, USA. Anatomically, she is very similar to modern frogs. The most ancient famous fossil worm, Ecaecilia Micropodia is also a view of the early Yura, and also found in Arizona. The ancient famous Salamandra is the view of BeiyanerPeton Jianpingensis from Verkhneurous sediments in Northeast China.

Conmptions are traditionally divided into three detachments; However, the extinct family of Salamandropod-like amphibians, Albanerpetontidae, is also included in this overcurrent. Moreover, the jumping also includes the fossil proto-frog of Triadobatrachus from Triass.

Evolution

In an evolutionary attitude, amphibians originated from the ancient cycular fish and gave the beginning of the representatives of the premature class. The most primitive detachment of amphibians are considered tailed. Tailed amphibians are most similar to the oldest representatives of the class. More specialized groups are parsedly amphibians and guise.

The origin of amphibians is still being disputes and according to the latest data, amphibians come from the ancient cycular fish, specifically, from the ripidism detachment. According to the structure of limbs and skull, these fish are close to fossil amphibians (Steodacemflam), which are considered to be ancestors of modern amphibians. The Archaic Group itself is ichthyoragehydes, which retain a number of features characteristic of the fish - the tail fin, rudiments of gill covers, organs corresponding to the organs of the side line of fish.

Basic aromorphoses

1. The appearance of the five-pall limb.
2. Development of lungs.
3. The presence of a three-dimensional heart.
4. Formation of the middle ear.
5. The appearance of two circles of blood circulation

see also

Notes

1. Amphibian Species of the World (eng.). Amphibian database. Darrel Frost And The American Museum of Natural History. Date of appeal March 13, 2012. Archived June 22, 2012.
2. Amphibian class, or amphibians: general characteristics (Neopr.) Archived on June 22, 2012.
3. Classis Amphibia (L. Ya. Borkin, 1992) (Neopr.) . Date of appeal March 13, 2012. Archived June 22, 2012.
4. // Encyclopedic Dictionary of Brockhaus and Efron: in 86 tons. (82 t. And 4 extra). - St. Petersburg. , 1890-1907.
5. Workshop on vertebrate zoology. Opening of amphibian (Neopr.) . Archived on August 4, 2012. Checked July 16, 2012.
6. Lymphatic hearts // Big Soviet Encyclopedia / Ch. ed. A. M. Prokhorov. - 3rd ed. - M.: Soviet Encyclopedia, 1973. - T. 14: Kuna - scrap. - P. 450. - 629,000 copies.
7. Nikitenko, 1969. Ground brain amphibians (Neopr.) . Biology and medicine. Date of appeal March 13, 2012.

In this article, we will talk about the numerous group of the most ancient animals living on our planet - about amphibians, or how else they call them about amphibians, or rather, we will briefly imagine the types of amphibians inhabiting the planet Earth.

Types of amphibians and their diversity

So, amphibia (lat. Amphibia) is a rather extensive class of four-legged vertebrate animals, considered primitive and occupying an intermediate place between water spinal and ground vertebral animals. In total, there are currently more than 6,500 modern species of amphibians who settled around the globe. In Russia, for example, only 28 representatives of the class under consideration are registered, but, for example, there are about 250 types of amphibians in Madagascar, as they say all sizes and masters.

The word "amphibian" occurred from the ancient Greek "Amphíbios" and literally means "two kinds of life" or "both types". Previously, this term was applied to animals that are able to lead a normal lifestyle, both on land and in water, such as laston-either. Later, this term began to apply to the four-legged vertebral animals that are not related to amniotes (higher vertebrate). Currently, all amphibians are divided into 4 subclasses, 3 of which today are completely extinct. Let's briefly consider the classification of existing, and ever existing on earth amphibians:

• Labyrinthodontics (lat. Labyrinthodontia) - a fully extinct subclass, which existed in Paleozoic and early Mesozoic periods:

• Anthraracosaurs;

• Colopiteids;

• Doscepondyl;

• Tonclothing (lat. Lepospondyli) is a fully extinct subclass that existed in the Paleozoic period:

• Microsauria;

• Acheronsiscidae;

• Nectridea;

• ADELOSPONDYLI;

• Lysorophia;

• Aïstopoda.

• Batrahozavra or otherwise reptomorphs (lat. Batrachosauria) - a fully extinct subclass that existed in the period from late Devon to the late Perm period:

• Anthracosaurs (Lat. Anthracosauria);

• Seymuriamorphs (lat. Seymouriamorpha);

• Conmpusive (Lat. Lissamphibia) - a modern subclass of amphibians, which includes all types of amphibians currently existing - Tritons, Zab, Salamander, Frogs and worm (Cecilia):

• The detachment of heavy amphibian (lat. Anura) is all frogs and toads belonging to more than 5,600 types of amphibians from 48 well-known families;

• The detachment of amphibians (lat. Caudata or otherwise Urodela) is all now living salamanders and tritons belonging to more than 570 types of amphibians from 10 families;

• A squad of a naked amphibian (lat. Gymnophiona or otherwise APODA) is modern worms, animals are similar in the rainwrites, which are about 190 species, and they belong to 10 families.

Crocodile Triton

As you yourself understand, the types of amphibians inhabiting our entire planet, despite the fact that many have already extinct long ago, there are still a great many - hundreds and even thousands. All of them look completely different. Some differ in average sizes, while others are very miniature. Some bright and smartly painted, while others, on the contrary, have a dull camouflage color. Some are not poisonous, while others are quite dangerous not only for small or large animals, but also for a person.

So, for example, a tiny, only 2-3 centimeter bright yellow frog, inhabiting in the rainforest of Colombia, with a loud name, terrible leisure (lat. Phylobates terribilis) can destroy not one person. The fact is that its skin is covered with a poisonous mucus containing the toxic substance Batrahotoxin. Local Indians use this mucus to make poisoned arrows. They call this frog "Coke". The poison of one such a frog is enough for 50 poisoned arrows, and in order to kill one person just a total of 2 minutes. Purified poison of this amphibian.

Some kinds of amphibians prefer wet places, others alternate staying in the water with finding on land, thirdly most of their lives take place on trees, and in the fourths - exclusively in water. And some amphibians live in fresh water, and others only in nautical salty, like, for example, sea toad (lat. Bufo marinus). Later we will look at the individual types of amphibians, their habitat and lifestyle.

Some types of amphibians fall into prolonged hibernation with the onset of extreme conditions for them, while others wake up the whole season and feel great at the same time. Some are active at night, while the other day.

Axolotl

Despite the fact that the overwhelming majority of these animals prefers warm conditions, and even hot, some kinds of amphibians are able to transfer quite a long-term freezing or drying. There are amphibians who are able to restore or "grow" (regenerate) lost parts of their body.

In fact, all types of amphibians, as you understand, cannot be devoted to one article, since there are a huge amount of them, and each of them has their own individual features.

Next, we will continue this large topic, and we will definitely tell you if possible, about certain types of amphibians, i.e. Defend each of them a lot of new interesting articles. We hope that you were interested. And before the meeting on the pages of the "underwater world."

In conclusion, I want to recommend watching video scenes, which will introduce you to some interesting types of amphibians. And after the video, you are waiting for links to new articles, which will tell a lot of interesting things about the amazing representatives of the Amphibian world.

Modern fauna of amphibians, or amphibians, is not small - less than 2 thousand species. Throughout life or at least in a larval state, amphibians are necessarily associated with an aquatic environment, since their eggs are deprived of shells that protect the drier action. Adult forms for normal livelihoods need constant moistening of the skin, so only inhabit the reservoirs or in places with high humidity.

Amphibians in morphological and biological features occupy an intermediate position between actually aquatic and actually terrestrial organisms.

The origin of amphibians is associated with a number of aromorphosis, such as the appearance of a five-palpal limb, the development of the lungs, the separation of the atrium into two chambers and the emergence of two circles of blood circulation, the progressive development of the central nervous system and sense organs.

Frog - a typical representative of amphibians

Frog - amphibian (non-reptile), a typical representative of the Amphibian class, on the example of which is usually given a class characteristic. A frog has a short torso without a tail, elongated hind limbs with swimming pools. The forelimbs, unlike the rear, have significantly smaller dimensions; They are four fingers instead of five.

The structure of amphibians

Skeleton and muscles

Amphibian body cover. The skin is naked and always covered with mucus, thanks to a large number of mucous multice glazed glands. It performs not only a protective function and perceives external irritation, but also participates in gas exchange.

Skeleton amphibians. The spinal column other than the torso and tail departments for the first time in the evolution of animals, cervical and sacral departments appear.

The cervical department has only one ring-shaped vertebra. Then follows 7 torso vertebrae with side processes. In the sacral division, too, one vertebra, to which the bones of the pelvis are characterized. The head of the frog is represented by Wrostil - the formation consisting of 12 talented vertebrae. Between the bodies of the vertebrae, the remains of chord are preserved, there are upper arcs and a faint process. There are no ribs and chest amphibians.

In the skull, significant carbage remains remained, which causes the similarity of amphibians with cyzerfisces. The skeleton of free extremities is dismembered by 3 departments. The limbs are associated with the vertebral post through the bones of the belts of the limbs. The front limb belt includes: yard, two ravene bones, two clavies and two blades. The belt of the hind limbs is represented by the accrete pelvic bones.

Musculature amphibians. Skeletal frog muscles can ensure the movement of body parts due to the reduction. The muscles can be divided into groups of antagonists: flexors and extensors, leading and discharge. Most muscles are attached to the bones of tendons.

The internal organs of the frog lie in the body cavity, which is lined with a thin layer of the epithelium and contains a small amount of fluid. Most of the body of the frog is occupied by the digestive bodies.

Digestive system of amphibians

In the mouth of the frog, there is a language that is attached to its forefront and animals thrown it when catching mining. On the upper jaw frogs, as well as in the sky bones there are undifferentiated teeth, in which the resemblance to fish is manifested. Salus does not contain enzymes.

The digestive channel, starting with the rotoglota cavity, turns into a throat, then into the esophagus and, finally, in the stomach that goes into the guts. The duodenum lies under the stomach, and the rest of the intestines are arched with hinges, then go to the rear (straight) intestine and ends with a clock. There are digestive glands: salivary, pancreas and liver.

Separational system of amphibians. Dissenlation products are allocated through the skin and light, but most of them are highlighted by the kidneys. From the kidneys along the ureters urine is displayed in a clock. For some time, urine can accumulate in the bladder, which is located at the abdominal surface of the Cloaca and has a connection with it.

Respiratory system for amphibians

Amphibians breathe both light and skin.

Light are represented by thin-walled bags with a cellular inner surface. The air is pumped into the lungs as a result of the injection movements of the bottom of the rotoglota cavity. With a diving frog, air filled with air filled with the role of a hydrostatic organ.

Speed-shaped cartilage appear, surrounding the Gundy slit and the voice ligaments stretched on them, are available only in males. Strengthening sound is achieved by voice bags formed by the mucous membrane of the oral cavity.

Blood system of amphibians

The heart is three-chamber, consists of two atrial and ventricle. Alternately, both at the sortia are reduced, then the ventricle. In the left atrium, blood is arterial, in the right - venous. In the ventricle, blood is partially mixed, but the structure of blood vessels is such that:

• The brain gets arterial blood;
• venous blood enters lungs and skin;
• in the whole body, the blood comes mixed.

Amphibians have two circle of blood circulation.

Venous blood in the lungs and skin is oxidized and enters into the left atrium, i.e. A small circle of blood circulation appeared. From the whole body, venous blood enters the right atrium.

Thus, the amphibians have formed two circle of blood circulation. But since the mixed blood is mainly incredible into body organs, the intensity of metabolism remains (as well as fish) is low and the body temperature differs from the environment.

The second circle circulation appeared at the amphibians due to their adaptation to breathing with atmospheric air.

Nervous system

The nervous system of amphibians consists of the same departments as fish, but in comparison with them has a number of progressive features: greater development of the front brain, the full separation of its hemispheres.

10 pairs of nerves come out of the brain. The appearance of amphibians, accompanied by a habitat and out of water to land, was associated with significant changes in the structure of the senses. The eye appeared blurred lens and convex cornea, adapted to the vision on a fairly distant distance. The presence of eyelids protecting the eyes from the drier action of air, and the blinking meal point to the similarity in the structure of the eye of amphibians with the eyes of real land vertebrates.

In the structure of the hearing authorities, the development of the middle ear is of interest. The outer cavity of the middle ear is closed by the drummeal, adapted to the capture of sound waves, and the inner cavity is the Eustachiev pipe opening into the throat. In the middle ear there is a hearing bone - stirring. There are external and internal nostrils in the sense of smell. The body of taste is represented by taste kidneys in the language, sky and jaws.

Reproduction of amphibians

Amphibians separatogs. The floor organs are paired, consist of a slightly yellowish seeds in the male and pigmented ovaries in the female. From the seeds are deposited by removing ducts, penetrating the front of the kidney. Here they are connected to the blades and open in the ureter, functioning as well as the seedwork, and opening into a clock. Eggs from the ovaries fall into the cavity of the body, from where through the eggs opening in a clock, are output.

In the frogs expressed a sexual dimorphism. Distinctive signs of males are tubercles on the inner finger of the front legs and voice bags (resonators). Resonators enhance sound when squabbing. The voice first appears in amphibians: it is related, obviously with life on land.

The development of a frog, as in other amphibians, occurs with metamorphosis. Larms of amphibians are typical water inhabitants, which is a reflection of the lifestyle of ancestors.

To the peculiarities of morphology, talkers having an adaptive value in accordance with the conditions of habitat are:

• special apparatus on the bottom side of the head, which serves to attach headstoves to underwater subjects;
• longer than an adult frog, intestine (compared to body sizes). This is due to the fact that the headasting consumes vegetable, and not an animal (as an adult frog) food.

The features of the organization's headstuffs that repeat the signs of ancestors should be recognized as a fishery shape with a long tailflower, the absence of five-way limbs, outdoor gills, side line and one circle circulation. In the process of metamorphosis, all organ systems are rebuilt:

• Grow limbs;
• zabras and tail are cut;
• intestines shortened;
• the nature of the food and chemistry of digestion, the structure of the jaws and the whole skull, the skin;
• the transition from gill breathing to the pulmonary, deep transformations occur in the circulatory system system.

The rate of development of tadpoles depends on temperature: the hotter, the more faster. Usually, the turning tower in the frog is required for 2-3 months.

Mature of amphibians

Currently, the class of amphibians include 3 detachments:

• Tailed;
• taught;
• ruthless.

Tailed amphibians (Tritons, Salamandras, etc.) are characterized by an elongated tail and pair short limbs. This is the least specialized forms. Little eyes, unaware. Some of some life saves gills and gill gaps.

W. chisty amphibians (Toad, frogs) The body is short, without a tail, with long rear limbs. Among them there are a number of species that are used in food.

To the detachment Nude amphibians Conditions are inhabited in tropical countries. Their body is drawn, devoid of limbs. Feed worms with rotting plant residues.

On the territory of Ukraine and the Russian Federation, the largest of European frogs - the frog of the lake, the length of which reaches 17cm, and one of the smallest chickened amphibians - ordinary quix, having a length of 3.5-4.5 cm. Adult quanks usually live on trees and have special discs at the ends of the fingers to attach to the branches.

Four kinds of amphibians are listed in the Red Book: Triton Karpathian, Triton Mountain, Toad, reed, frog is angry.

The origin of amphibians

Amphibians include forms whose ancestors are about 300 million. Years ago left the water to land and adapted to new terrestrial living conditions. From fish, they were distinguished by the presence of a five-plated limb, lungs and related characteristics of the circulatory system.

With fish, they were united:

• Development of larvae (headstuffs) in aquatic environment;
• the presence of the larvae of gill cracks;
• the presence of outdoor gills;
• the presence of a side line;
• the absence of germinal shells during embryonic development.

The ancestors of amphibians among the ancient animals are counted by cyzer fish.

All data from comparative morphology and biology indicate that amphibian ancestors should be sought among the ancient cyzer fish. Transitional forms between them and modern amphibians were fossil shapes - Steodacephali, existing in coal, Perm and Triassic periods. These ancient amphibians, judging by the bones of the skull, were extremely similar to the ancient cyzer fish. Characteristic signs of them: shell bone shell bones, sides and stomach; Spiral valve guts, like sharul fish, no vertebral bodies.

Steodacephali were nightly predators who lived in fine water bodies. The outlet of the vertebrates on land was accomplished in the Devonian period, distinguished by a dry climate. During this period, the advantage of those animals that could move from drying the reservoir to nearby are the advantage.

The flourishing (period of biological progress) of amphibians falls on the coal period, smooth, wet and warm climate of which was favorable for amphibians. Only, thanks to the exit, the vertebrae was obtained in the future to develop progressively.

The skin was covered with scales, there was a swimming blade on the tail, the remains of the gill lid. However, they already had five-way endeds, with which they could periodically crawl into the land and move along it.

The first amphibians appeared on Earth in the middle of Paleozoa-Skoy Era. These were ichthyosthegia. From them occurred steadocepha - an extensive group of ancient amphibians who gave the beginning of a modern amphibian.

Representatives of the class of earthmovy-vertebral animals, leading water-terrestrial lifestyle. The ancestors of modern amphibians in the pro-process of evolution were the first to go to the land.

In connection with the development of the amphibians of the new, ground-air environment, their external and internal structure became more complicated. The limbs of modern amphibians consist of three departments, movingly connected between themselves, which contributes to active movement. Breathe amphibians lightand wet leather, Therefore, they only live in wet places. Have amphibians three-kamera heart. The blood circulation has two circles circles.

During long historical development, modern types of amphibians were formed. There are less than in other classes of vertebrates, approximately 4 thousand.

Leather

The skin of the amphibian naked, rich in the glands. The glands allocate many mucus, which reduces friction when swimming, and on land protects the body from drying. The skin plays an important role in breathing. Through a network, the capillaries are saturated with oxygen and exemption from carbon dioxide. Yado-twisted skin glands protect many amphibians from predators.

Language

Most of the amphibians have a sticky tongue that serves for catching small animals (cloves, worms, slugs).

Eyes

Eyeballs when swallowing contribute to pushing the edible lump in the esophagus.

Amphibian eyes are protected from drying and contamination by two centuries. The surface of the head is moistened to the secret of the tears. The cornea of \u200b\u200bthe eye is a bubble (and not flat, like fish), a crystal in the form of two-cap lens (and not a circle, like fish), so Zem-novels see further than fish.

Skeleton

In the spine-nickname, there were two new departments - cervical and sacral. Thereby ensures the moving joint with the body.

The front limb consists of three departments: Ple-cha, forearm and brushes. The back is from the hips, leg and foot. Powerful muscles are attached to the bones of the limbs, allowing amphibians to actively move-rouch on land.

Breath

In the ground conditions, amphibians in adult co-standing breathe lightly (they are weakly developed) and skin. In water, they completely switch to skin breathing.

Circulatory system

The heart of amphibian trother, consists of a ventricle and two atrials. Blood moves-smiling for two circles of blood circulation: small and large. In a small circle, the blood flows from the ventricle to the light, where it is enriched with oxygen and returns to the atrium, and from there in the ventricle. In terms of the large cro-gu, blood from the ventricle delivers oxygen and nutritional substances to all animal organs, and they take carbon dioxide and exchange products. Then the blood enters the right atrium, and then goes into the ventricle. Thus, in amphibian blood in the heart is mixed.

Metabolism

Due to the weak development of lungs and the movement of mixed blood in the body, the level of metabolism in amphibians are low. Therefore, they are cold-blooded Animals. The temperature of their body co-responsive to the ambient temperature. In handling conditions, the activity of amphibians is reduced, and they fall into a stupor. Winter amphibians in shelters on land or shallow water reservoirs.

Nervous system and senses

The nervous system and the senses organs are complicated. In the brain, the brain is well developed.

The hearing body is able to perceive the sounds in the air. Amphibians are formed by the middle ear with a drummeal and a hearing bone, which the efforts of sound oscillations.

All amphibian separations. Fertilization is more often outdoor. The females get into the water to the caviar, similar to the caviar of fish, which the male is pouring milk. Through some time from caviar hatching larvae - tadpoles having many common features with fish larvae. During the wrong months, the tadpoles pass the stage of in-concluded development and turn in the closed layers of amphibians.

Ocelessly, amphibians have views with direct development. These are Antilles and Caribbean leafy frogs. They are decking - the caviar to the Earth in the wet places. Already in Ikrinka, the embryo is more like a frog than a taller. They are born quite formed.

The most numerous group of amphibians - representatives of the detachment taught. Some of them constantly live near Moody ( ozernaya, pond, black frog).Others can leave water for large distances ( ostromorda, herbal frogs, toads) or live on trees (Kwakshi).

The frog is the most typical representative of amphibians - the object of many labo-guidance experiences, for which she is put on the territory of the University of Sor-Bonn (Paris) Para-Mint has been delivered. Another monument to La-Goachke is located in Tokyo. Material from site.

Most of the representatives of the Non-fellow squad ( cher-Vygi) dwell in the wet soil at a depth of 60 cm. To the detachment tail salamander, Tritons, Protea, Siren.

The amphibians in the numerical place in the supply chains of both water and ground ecosystems. They feed the amphibians by the comes and their larvae, as well as spiders, mollusa and fry fish. Among insects, which feed frogs and toads, a large number of rural and forestry time. One frog in the summer can eat more than a thousand harmful us. Many fish, birds, snakes, hedgehogs eat amphibians

For amphibians, like the first vertebrates, which came to the air from the water, the lungs appear as the respiratory organs. At the same time, the majority of species in the adult state loses the gills (some tailed amphibians remain). However, light amphibians do not have a sufficiently large surface in order to sufficiently provide tissue with oxygen. Therefore, the breath of amphibians is carried out not only with light, but also skin. Thus, it can be said that in adults of amphibians in respiration two organs participate: light and skin. Moreover, some types are absorbed to 50% oxygen.

Light amphibians represent a couple of oblong thin-walled bags having inside the fold. Their walls are permeated by a thick network of capillaries. In the lungs, oxygen penetrates into the blood, and carbon dioxide gas is distinguished from the blood.

In the mechanism of pulmonary respiration in frogs, the mouth cavity takes an active participation, and the nostrils are also involved in it. Inhale occurs when lowering the bottom of the mouth. In this case, the air is sucked through the nostrils and enters the rotoglotum cavity. Next, the nostrils are closed, the bottom of the mouth rises and the air pushes into the lungs. For exemption, the bottom of the mouth is again lowered, the nostrils open, and the air leaves the lungs. In exhalation, some abdominal muscles also participate. However, amphibians have no diaphragm, intercostal muscles, like mammals. Therefore, the leading role in suction and disposal of air from the lungs plays the bottom of the pharynx.

In the lungs there are the most venous blood from the camshaft ventricle of the heart. Here the blood is saturated with oxygen, becomes arterial and returns to the left atrium of the heart. Thus, amphibians in connection with the advent of the lungs there is a second circulation circulation. It is also called small, or pulmonary.

Since the amphibians breathe and the skin, the blood, which flows from the skin, is also arterial and goes to the heart. But at the same time, it flows into the right atrium, where all the venous blood falls from body tissues. Next, from both atria, the blood gets into the ventricle of the heart, where it is partially mixed, as the ventricle among the amphibians only one. Due to the fact that the organs and tissue of the body are not supplied with arterial blood from amphibian low metabolism, and they are cold-blooded animals.

Smooth leather smooth. She has no scales or other dense formations. Therefore, gases are easily penetrated through it. In addition, the skin is constantly moistened, and this is important, since oxygen, to penetrate the skin into the blood, must first dissolve in water. If the frog is driving, it may suffocate.

It is especially important to skin breathing when amphibians under water. Thanks to him, they can raise less frequently to the surface. Many frogs winter under water in a state of stupor. In this case, the metabolism slows down, and they do not need a lot of oxygen, and the one that is necessary, they get from the water through the skin.

Golobastikov (larvae of frogs) and certain types of amphibians are external or inland gills. At the headastricians, the external gills appear first, then they become internal. As the metamorphosis (turning it into a frog), the lungs are formed, and the gills are absorbed.