A frog is a typical representative of amphibians. Using the example of this creature, it can be easily explored the most important characteristics of the class. To do this, we will look at the inner and external structure of the lake frog, which will further help us understand the features of the structure of all amphibians.
External structure
The external structure of the frog and habitat is two inextricably linked unified chains. After all, it is no secret that the appearance and structure is due to the place and lifestyle of the animal.
The lake frog lives on the shores and in the reservoirs, which has become its name. However, the river, swamp, pond and other places can be played as a place of residence.
The external structure of the frog is very simple. A wide flat head goes into a small body with a reduced tail. The frog has very short front limbs equipped with four fingers. The hind limbs, on the contrary, are elongated and have five fingers.
Pokrov animal
Speaking about the external structure of the frog, it is necessary to pay attention to its skin. The body of the amphibian creature is covered with a smooth skin, on the surface of which the impressive amount of glands is located, which constantly distinguish the mucus. The secret lubricates superficial covers, helping to keep moisture, contributing to gas exchange. The mucus also protects the animal from penetration into the body of malicious microorganisms.
Thin leather of amphibian protects the body, and also participates in gas exchange. Features of the external structure of the frog are associated with the image of her life. For example, water in the body of the animal comes only through the skin. It is for this reason that the frog must mostly be in dampness or in water.
Characteristics of the external structure of the frog: body departments
Speaking about the external structure of the frog, the following body departments can be distinguished - the rear and forehead limbs, head and torso. One of the features of the amphibian is almost a complete lack of neck. In general, the border of the separation between the torso and the head is not clear, or rather, it is practically no. The body of the frog is a little more head. An animal is completely absent.
A large head has a big eyes. They are covered with transparent eyelids, designed to prevent damage, drying and clogging.
The nostrils are located below the eye. In general, it is worth noting that the eyes and nostrils are not closely located close to each other in the top of the head. The fact is that during swimming, they are constantly over the surface of the water. Thanks to this, the animal can breathe and see everything that happens above the lake.
The upper jaw of frogs is armed with a number of small teeth. But they have no ears. Their roles are engaged in eardies, located behind the eyes of the animal.
Color animal
Describing the external structure of the frog, pay attention to its color, which is largely determined by the habitat. Most amphibian representatives are mimicarized under external nature. And some varieties even have special cells that are able to change the skin of the skin depending on the environmental conditions. Therefore, often the color of the animal repeats the drawing of the places where the creature lives.
In the tropics there are amphibians having a bright colors. This suggests that the animal is very poisonous. This is exactly what scares enemies from such frogs.
Limit of amphibian
Running the external structure of the lake frog, we mentioned the unusual limbs of the animal. The peculiarity of their structure is related to the fact that the front legs are used to land and for support in a sitting position. The hind limbs are much stronger and longer than the front. For movement on water or by land, rear paws are used. For the extremities of the animal there are membranes, significantly facilitating movement in water. The external structure of the frog is such that it makes it possible to move the animal not only in water, but also on land.
Some representatives can even climb trees or plan in the air. Frogs have a lot of fixtures depending on the habitat. Some nature gave special suction cups, so they stick to any surface, others can be under the thickness of sand or soil for a long time. In all these cases, their strong limbs help to move amphibians.
The skeleton of frogs, according to biologists, is very similar to the skeleton of perch. However, due to the characteristics of the lifestyle there are significant differences. As we know, frogs have limbs. The front is attached to the spine with peculiar bones. But the rear is connected to the spine with the help of hip bones. The amphibian representative is much easier than fish, since it has fewer bones.
The spine Frogs in total consists of nine vertebra. At the same time, it is divided into four departments: cervical, sacral, tail and torso. But the ribs in the animal are absent.
Digestive system
Frogs and toads feed insects and small invertebrates. Such animals belong to predators. Sometimes they even be bent with their relatives. The frog will be fluttered in a secluded place. As soon as the victim approaches, they are shooting with the tongue and absorb prey.
Blood amphibian
Blood is a connecting tissue that performs a very important role in any body. It is she who tolerates the products of exchange and nutrients. As is known, blood consists of red blood cells and leukocytes.
The external structure and the form of red blood cells differs from human red blood cells. In the animal they are oval and have a kernel. But people have red blood cells bicked and deprived of nuclei. This increases the area that oxygen molecules occupy. So, the blood system of people is more perfect. In addition, red blood cells are larger, and they are much smaller than in human blood. All this suggests that oxygen needs amphibian in much smaller quantities than mammals. And the reason for this is the ability to assimilate a part of the required oxygen with the surface of the skin.
The respiratory system of frogs has its own characteristics. Breathing amphibians not only with the help of lungs. In this process, the skin also takes active attention. As you could make sure the external covers play a crucial role in the life of amphibians. Light animal is thin-walled paired bags that have a cellular internal structure and a strongly branched network of vessels.
How does breath come? Amphibians use valves that close and open the nostrils. During the breath, the nostrils and lowering of the rotogloty cavity occurs. So the air falls inside. In order for he further hit the lungs, the nostrils are closed, and the bottom of the rotogling, on the contrary, rises. Exhaust is carried out due to the work of the walls of the lungs and the movement of the muscles of the belly.
Sense organs
The sense of amphibians have their own characteristics, due to the fact that animals live in land. Organs helps to navigate the side line organs in space. Their largest number is on the head. Externally, they resemble two stripes that pass along the body.
On the skin of amphibians are temperatures and pain receptors. The nose is working as a challenge body only if it is located above the water. In the water, nostrils are always closed. Even the respiratory system is completely adapted to habitat amphibians both in water and on land.
Nervous system of frogs
But the nervous system of amphibians is not too developed. It is largely similar to the nervous system of fish. In this respect, amphibians are not far away from the evolutionary staircase. The brain of amphibians consists of five departments: front, medium, intermediate, oblong brain, cerebellum. By the way, the latter is poorly developed due to a sedentary lifestyle of the animal. But the front brain consists of two hemispheres and, on the contrary, is sufficiently developed.
Amphibious - The smallest class of vertebrates, presented by 3 detachments:
Tailed (salamanders and tritons);
A naked (worm);
Cheerful (frogs, toads, garlic, etc.).
Structure.As the inhabitants of sushi, amphibians breathe lungs, have two circles of blood circulation, three chamber hearts; Amphibians are planned by the separation of blood on arterial and venous. All amphibians have smooth thin skin. The skin is rich in skin glands excreasing mucus. The body is divided into head, torso, tail (in tailed) and five-plated limbs. Moving amphibians with fifth-type limbs with spherical joints. The temperature of their body depends on the temperature and humidity of the environment. All amphibians are powered by mobile mining. Amphibian eyes look like fish eyes. The highest amphibians have upper and lower mobile events. The sense of smell function only in the air. In the hearing body, a new department is a secondary ear. The conname authority is the skin containing tactile nerve endings. Water representatives and headstands have side-line organs.
Reproduction.All amphibian separation. During the breeding period, the ovaries filled with mature eggs are filled with almost all the abdominal cavity in females. Their eggs are deprived of shells protecting them from drying, and, as a rule, cannot develop outside the water. In this regard, the amphibians develop a larva that dwells in water. 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. In the life cycle of amphibians, 4 stages of development are clearly distinguished: an egg, a larva (taddastic), a period of metamorphosis, an adult sex.
Triton biology.The smallest Triton of our fauna: the maximum total length is 89 mm (body length is 58 mm). The skin in the reservoirs is smooth, the land is weak. The spinal ridge in males is extontal, continuously (without removing) passes into the tail. The tail in males is slightly shorter or equal to the length of the body, the females are almost equal or a little longer. In the marriage period on the fingers of the hind limbs in males they grow blades. Olive-green coloring or brown, with dark specks or without them. On the sides of the head 3 longitudinal dark strips, especially noticeable through the eye. Belubo yellowish or orange, with small dark stains. The tail in males in the marriage has a blue lane with a pearl brilliance and orange kaymo from below. Sky teeth in the form of two longitudinal closely located parallel rows, a little diverging from behind. In the water bodies feed the docks (including larvae), other insects, crustaceans, mollusks, etc.; On land, mainly beetles, caterpillars of butterflies, many-facets, spiders, rainworms and other animals. The larvae eat daphnium, larvae of mosquitoes and other small water invertebrates. Tritons themselves become the prey of various predators. They feed fish, amphibians, reptiles, birds and some water invertebrates (larvae). Many inner fertilization. Otherwise, they are similar to other amphibians.
Biology frogs.The selection authorities include paired kidneys and ureterals, urinary, bubble. The kidneys on the origin of the primary, by location - torso. From the bladder urine is removed through a clock. The digestive system of amphibians is largely similar to that fish. The intestine ends with a cloacon where the bladder and sex gloomy ducts fall. The prey is fuckless amphibians catch with the help of a sticky language and swallow entirely. Food serve mainly insects, mollusks. The female mosques in the water caviar, the male simultaneously produces seed fluid. The shell of fertilized caviar swells and compacted. Development deadlines Lichinbk from caviar depend on ambient temperature. For amphibians, development is characterized with metamorphosis. Larvae Frog - Golovascular has outdoor gills, one circle circulation, side line and tail fin, which indicates the origin of amphibians from fish.
The biology of the toad.The torso is short, the neck is not expressed, there is no tail, the paired limbs are well developed, and the hind limbs are two to three times more than the front and serve for characteristic movement by jumping. The body is divided into head, torso and five-plated limbs. The head is movable, connected to the body. The skeleton is divided into departments: axial skeleton (spine); Skeleton head (skull); Skeleton of paired limbs. The limbs are usually primary five plates. Bones of forearm and tibia merge. All bones of the back limb are very elongated, forming powerful levers for mobile jumps. On the head there may be skin ossification associated with a thorough way of life, for example, a garlic. These formations can take a bizarre form of a bone helmet. The eyes of frogs are located so that it can see the district almost 360 degrees. Taste organs are developed weakly. Amphibians are able to distinguish between four types of flavoring substances well - sweet, bitter, sour and salty. The bodies of the amphibians, which serve on bulk-shaped calves, are concentrated in their nasal cavity, in the mucous membrane of the sky and language. The intensity of metabolism in amphibians is very low, and the body temperature is inconvenient. The sexual ripening of most frogs occurs at the age of 6-12 months. At this time, males start singing in the evenings. Females are usually much larger and thicker males.
\u003e\u003e The inner structure of the frog
§ 46. Internal structure of the frog
Muscles.
The structure of the muscular system of the frog is much more complicated than the fish. After all, the frog not only floats, but also moves on land. Thanks to the contractions of muscles or muscle groups frog may make complex movements. It is especially well the muscles of the limbs.
Digestive system amphibians has almost the same structure as fish. In contrast to the fish, the render of it does not open out, but in its particular expansion, called Cloaca. The ureterals and output of the reproduction organs are also opened in Cloacu 87 .
Respiratory system.
The frog breathes atmospheric air. For breathing is light and skin 89 . Lungs have kind of bags. Their walls contain a large number of blood vessels in which gas exchange is performed. The throat of frogs is delayed several times per second, due to which a sparse space is created in the oral cavity. Then the air penetrates through the nostrils into the oral cavity, and from there in the lungs. Back it is pushed under the action of musculature of body walls. Light frogs are poorly developed, and skin breathing is just as important as the pulmonary. Gas exchange is possible only with wet skin. If the frog is placed in a dry vessel, then the skin is shortly dries and the animal may die.
Immersed into the water, the frog is entirely moving into skin breathing.
Circulatory system.
The heart of the frog is placed in the front of the body, under the sternum. It consists of three chambers: ventricle and decrease alternately, both atrium, then the ventricle 89 .
In the heart of the frog, the right atrium contains only venous blood, left - only arterial, and in the ventricle blood to a certain degree mixed.
The special location of the vessels, originating from the ventricle, leads to the fact that only the brain of the frog is supplied with pure arterial blood, and the whole body gets mixed blood.
The frog's blood from the ventricle of the heart flows through the arteries to all organs and fabrics, and of them on the veins, it reaches the right atrium - this is a large circle of blood circulation. In addition, blood from the ventricle enters the lungs and into the skin, and from the lungs back to the left atrium of the heart is a small circle of blood circulation. All vertebrates, besides fish, two circles of blood circulation: small - from the heart to the respiratory organs and back to the heart; Big - from the heart of the arteries to all organs and from them back to the heart.
The exchange of substances in amphibians flows slowly.
The body temperature of the frog depends on the ambient temperature: rises in warmth time and decreases in the cold. When it becomes very hot in the air, the body temperature of the frog decreases due to the evaporation of moisture from the skin. Like fish, frog and others amphibious - cold-blooded animals. Therefore, when cooling the frogs become inactive, they seek to climb so much, and for the winter and completely sit down in the hibernation.
The central nervous system and the organs of the senses of amphibians consist of the same departments as fish 90. The front brain is developed stronger than among fish, and in it you can discern two bloatings - big hemispheres. The body of amphibians close to Earth, and they do not have to maintain balance. In this regard, the cerebellum, controlling the coordination of movements, they are developed weaker than that fish 90 .
The structure of the senses corresponds to the ground environment.
For example, blinking with centuries, the frog removes the damned to the eye of the dust and wets the surface of the eye.
Like fish, the frog has an inner ear. However, in the air, sound waves apply to much worse than in water. Therefore, for better hearing, the frog has developed more than the secondary ear. It begins that it takes the sounds with a drummeal - a round film with a circular film behind the eye. From it, sound oscillations through an auditory bone are transmitted to the inner ear.
1. What is the difference between the muscular frog system from the perch muscles? What are the examples of these differences?
2. Why is an adult frog, which has no gills, does not choke under water?
3. What are the peculiarities of the nervous system and the senses of the frog in connection with the life of land?
4. Using drawings 75
, 89
, Explain what is the main difference between the circulatory system of amphibians from the circulatory system of fish.
Biology: animals: studies. for 7 cl. environments shk. / B. E. Bykhovsky, E. V. Kozlova, A. S. Montchadsky et al.; Under. ed. M. A. Kozlov. - 23rd ed. - M.: Education, 2003. - 256 p.: Il.
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