A lizard is a terrestrial cold-blooded animal whose body is adapted to the land mode of life. It lives in forests, steppes, deserts, mountains. The small graceful body of the lizard is covered on the outside with numerous horny scales; breathing is exceptionally pulmonary. She moves with the help of her legs, touching the tail and the body of the earth (creeps). Why can't a lizard breathe skin? The answer to this question will help the study of the structural features and lifestyle of one of the typical representatives of the reptile class.
Lizard
In sunny places, among grass and branches, on warm stones, you can meet a small elegant animal. This is a fast or ordinary lizard. The length of her slender body reaches 15-20 cm (along with the tail). Coloring - greenish-brown with black spots of different sizes. The outer layer of dry, firm skin is thickened, keratinized in the form of scales on the entire body and shields on the head. At the fingertips there are claws, with them a lizard clings to the bark of trees, stones when climbing. The scaly cover protects the body from drying out and damage. Air does not penetrate through it, which is why the lizard cannot breathe in the skin, uses only the lungs. They supply the body with oxygen, which is necessary for the cells of the body to receive energy. In the warm season, the lizard molts several times. Scales inhibit the growth of the animal, so the keratinized layer is exfoliated by flaps and a new one appears.
Lizard structure
The body of the lizard wriggles and often comes in contact with the ground. This method of movement gave the name to a class of animals - reptiles, or reptiles. This group includes a squad of scaly, a suborder of lizards. Numerous representatives have common features that allowed them to be combined into one group. Consider the external structure of a lizard:
- the body consists of a head, trunk, long tail, four limbs;
- the head section pointed in front passes into a short thick neck;
- the eyes are protected by the upper and lower eyelids, they are constantly wet due to the translucent blinking membrane - the third century;
- on the head is a pair of nostrils through which air passes;
- the external opening of the hearing organ, covered by the eardrum, is located behind the eyes;
- organ of touch - a long tongue forked at the end;
- the limbs consist of three sections, five fingers on the legs, between them there are no membranes.
Lizard Features
Reptiles are complex land animals, some of which have adapted to the aquatic lifestyle. There are external features that distinguish lizards from amphibians:
- neck between head and torso;
- there are no swimming membranes, claws on the toes of short legs;
- dry skin with a horny cover;
- third eyelid.
At night, lizards hide in holes, under stones or stumps, in the autumn in temperate latitudes, like frogs, hibernate. Amphibians in this period, gas exchange continues through the thin integument of the body. Why can't a lizard breathe skin like a frog? Reptiles have lost the ability to exchange gas through the skin during evolution. However, the metabolism in the body of reptiles is slower than in birds. In the warm season, the lizard is mobile, hunts for prey, and when cold, it becomes sluggish, eats less.
Lizards breath
In the thoracic part of the body of the lizard, ribs are attached to the spine to protect the heart and lungs from damage. Air through the nasal openings enters the oral cavity, passes into the larynx and trachea, and then into the bronchi. Light lizards are similar to frog breathing bags, but have a more complex structure. With the expansion of the chest, air is absorbed, and with narrowing, exhalation occurs. Intercostal and abdominal muscles are involved in these movements. In the lungs, air fills the cells, separated by partitions, densely pierced by capillaries. Why can't a lizard breathe skin like a frog? In amphibians, naked wet skin is an additional respiratory organ, especially necessary during hibernation. Through the covers, oxygen from the air penetrates into the circulatory system, and carbon dioxide passes into the environment. The body of the reptile is covered with horny scales, in which there are no blood vessels. Therefore, there is no skin respiration in the lizard.
Ability to regenerate
The body of the lizard bends when it crawls, with the help of claws it clings to the slightest irregularities of the earth or bark. An animal can climb a tree trunk, on a rocky slope. In addition to the speed of movement, there is a protective color in harmony with the natural habitat. Some species have acquired the ability to change skin tones, others hiss menacingly, scaring away predators. A thick, muscular tail helps with movement and protects against attack. There is an interesting property that lizards possess. When the pursuer attacks them from behind and holds them by the tail, he easily breaks off and continues to wriggle for some time. The attacker is fascinated by this movement, and the lizard escapes in the mink or thickets of grass. Instead of the lost, the animal regenerates (restores) a new tail, shorter and thicker than the previous one.
Suborder of lizards
Representatives of this systematic group can be found in all climatic zones except the tundra and polar deserts. In the world there are over 5900 species united in families. Agamic species include species of lizards leading a woody or terrestrial lifestyle. Some are capable of planning a flight (genus Draco). The largest of the monitor family is Komodo (3 m).
Representatives of the chameleon family change their body color. Basilisk males have frightening ridges and spines along their backs. These lizards swim well and can run on water, staying on its surface due to impacts of webbed feet. The genus got its name because of its resemblance to the mythical monster Basilisk. Iguanas are large representatives of the suborder of lizards. So, the length of the common iguana is 1.9-2 m. The legs of small geckos and agamas are covered with many tiny outgrowths that help to grip with different surfaces, even with glass. In legless lizards, limbs are completely absent, but they differ from snakes in the mobile eyelids and the presence of a shoulder girdle in the skeleton.
Representatives of all families of lizards demonstrate perfect adaptation to certain habitats. They compensate for imperfect thermoregulation by hiding in shelters from overcooling and overheating. Hibernating, the lizards avoid the winter cold, in the hot desert they switch to a nocturnal lifestyle.