Once upon a time there was a frog

Of all the amphibians, the most known and familiar being is the frog. With green kvakushkoy, children are familiar with childhood from cartoons and fairy tales. Frogs are spread all over the world, and the color of them can not only be green. Many of them are poisonous.

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Frog is amphibian. On short front paws there are four fingers. On the rear more developed paws five fingers. On the claws there are no claws, and the fingers are connected by a leathery membrane. All species of frogs have a bifurcated sticky tongue. Thanks to their skin, they can live both in water and away from it. But they are found mainly in wet areas and in places where their habitats are ponds.

The female lays eggs in puddles of water. Larvae appear from eggs, they are called tadpoles. They can swim in the water, using the tails that they have. Tadpoles grow up quickly, and the tails disappear. In a colder climate, the embryo is black in color to absorb more heat from the sun. Some frogs lay eggs in small bags of leaves to save them from predators and provide them with the necessary moisture. Tadpoles feed on algae, which indicates that they are herbivores. Some species are carnivorous.

Tadpoles risk being easily caught by fish, birds, especially kingfishers, newts and predatory underwater beetles. Tadpoles of some species are toxic to predators. Some tadpoles have the ability to winter, and then metamorphose next year.

A frog is carnivorous. With her long sticky tongue, she deftly grabs her prey. Typically, frogs eat insects and other living things. She will not refuse from a small congenital. The frog's mouth is the beginning of the digestive system. On the upper jaw are the so-called maxillary teeth, which are used to grind food before swallowing. These teeth are very weak and can not be used to catch the victim. Chopped food through the esophagus enters the stomach, then enters the small intestine. Pancreatic juice and bile enter the intestine and mix with food.

Frogs spread all over the world, except for Antarctica, many oceanic islands and hot deserts. There are 4810 species of frogs. The frog has moist skin and lives in or near water. The rest, which stay away from water and have warty skin, are called toads. Taxonomically, they can be different, anatomically, there is practically no difference between frogs and toads.

Frogs are interesting amphibians, they differ from others in breathing. They can receive oxygen not only through the lungs, but also through the skin. Oxygen dissolved in moist skin can also be absorbed by them. Even if you deprive the frog of the lungs, it will breathe through the skin and will continue to live. This method of breathing makes frogs susceptible to toxins dissolved in water, and helps to reduce the population of frogs.

Frogs stand out among amphibians. Adults do not have a tail, and hind legs are more adapted to jumping, and not to walking. The body size of frogs is from 1 cm to 30 cm, the skin freely covers the body, since there is no connective tissue. The texture of the skin can be smooth or warty.

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They have three centuries. One of them is transparent, it protects the eyes under water, and two - translucent. On both sides of the head there is a tympanum that helps to hear. The Australian tree frog can jump about 50 times higher than its body length, about 2 meters. The ability to jump and the distance of a jump depends on the species. The muscular system is highly modified depending on the habitat of the frogs. In modern frogs, almost all the muscles participate in performing jumping movements, and only a few participate in the return of the body to its original posture. The muscles are significantly enlarged in size, and the muscles involved in the jump form are about 17% of the body weight of the frog. It is now assumed that frogs retain their energy by stretching their tendons, using them as a spring.

Most species of frogs use camouflage as their primary protective weapon. They know how to disguise themselves well, and this is another way to save them from predators. Warts and skin folds, as a rule, are found in terrestrial frogs, and tree frogs have smooth skin, so they can easily hide under the leaves. Some of them change color during the day and at night, light and humidity help in contracting and expanding pigment cells.

Many frogs are poisonous. All toads have a poisonous gland, called the parotid gland, it is located behind the eyes. The effect of poison can cause a state from irritation to hallucinations, seizures and narrowing of blood vessels. Indigenous South Americans extract poison from poisonous frogs. Alkaloid epibatidine, an analgesic, is 200 times more effective than morphine. It is believed that some chemicals released from frogs are useful in the treatment of HIV infection. Poisons of frogs are studied for the invention of therapeutic drugs. Secretions of the skin of some toads contain bufotoxins, especially bufotenin, which is psychoactive.

The skin contains a large number of blood vessels. When the frog is under water, oxygen is absorbed through the skin and transported directly to the bloodstream. On land for breathing, the lungs are used. Lungs resemble human lungs, but the muscles of the chest are not involved in breathing, the frog has no ribs and diaphragm.

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Frogs have a highly developed nervous system consisting of the brain, spinal cords and nerves. Many parts of the brain resemble the human brain. The body of the medulla oblongata is responsible for controlling the processes of digestion, respiration and other automatic functions. The cerebellum controls the coordination of the muscles and the position of the body. The relative size of the brain is smaller than that of the human brain. There are ten cranial nerves and ten pairs of spinal nerves. The ear has semicircular canals, which are responsible for balancing and orientation.

The sound that frogs of some species make is so loud that they can be heard for a kilometer. The frog call is unique to the species. Kinds of frogs that do not have vocal pouches and are not capable of producing loud noises, gather near the water and communicate in other ways. The main reason for frog singing is the desire of the male to attract the female. Males cry singly or in groups. All sounds are produced by males with a closed mouth. When frogs are in danger, they give a distress signal with an open mouth, which greatly amplifies the sound.

Frogs are a food source in China, the Philippines and France. Medical schools use them to study anatomy and physiology. Frogs are used in various branches of science. Galvani discovered a connection between electricity and the nervous system, studying the physiology of frogs. Robert Briggs and Thomas King cloned a frog in the technique of transmitting nuclear somatic cells in 1952, and then using this technique, cloned the Dolly sheep.

No one disputes the benefits of frogs, but their appearance in most people is disgusting. Once, due to lack of storage conditions, the frog was thrown into milk, so that it would not sour. This was facilitated by the presence of antibacterial substances on her skin. It's easy to imagine a reaction when you drink cool milk and at the bottom you see a frog.