Mammals are ... Mammal units. Types of mammals

Animals or mammals are the most highly organized vertebrate animals. Developed nervous system, feeding young, live birth, warm bloodedness allowed them to spread widely around the planet and occupy a wide variety of habitats. Mammals are animals that live in forests (wild boars, moose, hares, foxes, wolves), mountains (sheep, mountain goats), steppes and semi-deserts (jerboas, hamsters, ground squirrels, saigas), in soil (mole rats and moles) Oceans and seas (dolphins, whales). Some of them (for example, bats) spend a significant part of their active life in the air. Today it is known about the existence of more than 4 thousand species of animals. The groups of mammals, as well as the characteristic features inherent in the beasts - we will tell about all this in this article. Let's start with a description of their structure.

External structure

The body of these animals is covered with wool (its remains are even found in whales). Distinguish hair coarse straight (awn) and thin sinuous (undercoat). From pollution and stalling, the undercoat protects the awn. The mammalian wool cover can consist only of awn (for example, in deer) or from undercoat (as in moles). These animals periodically moult. In mammals, this changes the density of the fur, and sometimes also the color. In the skin of animals there are hair bulbs, sweat and sebaceous glands and their modifications (milky and odorous glands), horny scales (as on the tail of beavers and in rats), as well as other horn formations occurring on the skin (horns, hoofs, nails, Claws). Considering the structure of mammals, we note that their legs are located under the trunk and provide these animals with more perfect movement.

Skeleton

In the skull they have a highly developed brain box. In mammals, the teeth are located in the jaw cells. Usually they are divided into root, fangs and incisors. The cervical spine consists of almost all animals from seven vertebrae. They are interconnected among themselves, except sacral and two caudal, which, growing together, form a sacrum - a single bone. Ribs are articulated to the thoracic vertebrae, which are usually from 12 to 15. In most mammals, the forelimb belt forms paired shoulder blades and clavicles. Only a small part of the animals preserved crow's bones. The pelvis consists of two pelvic bones, fused with the sacrum. Skeleton of extremities - from the same bones and departments, as well as at other representatives of four-legged vertebrates.

What are the senses in mammals?

Mammals are animals that have ears, which help to catch smells, and also determine their direction. Their eyes have eyelids and eyelashes. On the limbs, belly, head are vibrissae - long hard hair. Animals with their help feel even the slightest touch to objects.

Origin of mammals

Like birds, mammals are the descendants of ancient reptiles. This is indicated by the similarity of modern animals with modern reptiles. In particular, it manifests itself in the early stages of embryo development. An even greater number of signs of similarity were found in them with the sparrow-lizards, extinct many years ago. Also for kinship with reptiles is the fact that there are animals that lay eggs that contain a lot of nutrients. Some of these animals have cloaca, developed crows and other signs of low organization. It is about the first-timers (oviparous). Let's talk about them in more detail.

Pervostveri

This is a subclass of the most primitive mammals living today. Along with the signs already mentioned, it should be noted that they do not have a constant body temperature. The glabellar glands of perivozerei do not have nipples. The cubs that hatched from the eggs lick the milk from the mother's fur.

In this subclass, one squad is allocated - Single Pass. It includes 2 species: echidna and platypus. These animals today can be found in Australia, as well as on the islands adjacent to it. Platypus is a medium-sized animal. He prefers to settle along the banks of rivers and leads a semi-aquatic life here. He spends most of his time in the hole he dug in a steep bank. The female platypus in spring lays eggs (usually two) in a special hole, equipped with a nested chamber. Echidnas are animals digging. Their body is covered with stiff hair and needles. The females of these animals lay one egg, which they place in a bag - a fold of skin, located on the stomach. The calf hatching from it, until then, is in the bag until the needle appears on the body.

Marsupial

The order of the Marsupials includes animals that give birth to underdeveloped cubs, after which they wear them in a special bag. They have little or no placenta. Marsupials are widespread mainly in Australia, and also on the islands adjacent to it. The most famous of them are the marsupial bear (koala) and the giant kangaroo.

Insectivores

Insectivores are a detachment that unites ancient placental primitive animals: hedgehogs, shrews, moles, muskrats. The muzzle at them elongated, there is an elongated proboscis. Insectivores have small teeth, and their feet are five-fingered. Many of them near the tail root or on the sides of the body have odorous glands.

Shrews are the smallest representatives of insectivores. They live in meadows, bushes, dense forests. These animals are gluttonous and attack small animals. In the winter time, they lay under the snow moves and find insects.

Moles are animals that lead an underground lifestyle. They dig with their forelegs numerous holes. In the mole, the eyes are weakly developed and represent black dots. In an embryonic state there are ears. The short thick coat does not have a definite direction and is snug when moving to the body. Moles are active all year round.

Chiroptera

The detachment of Bats or Bats includes small and medium sized animals that are capable of prolonged flight. In the subtropics and tropics, they are particularly numerous. The teeth of these animals are insectivorous . The most common in our country ushany, leather, evening. Representatives of bats live in attics of houses, in hollows of trees, in caves. In the afternoon they prefer to sleep in their shelters, and at dusk they go out to catch insects.

Rodents

This unit unites one third of the species of mammals that inhabit our planet today. To them belong proteins, squirrels, rats, mice and other animals of medium and small size. Rodents are mostly herbivorous animals. They have highly developed incisors (in each jaw - two), molars with a flat chewing surface. There are no roots in the incisors of rodents. They are constantly growing, self-sharpening and stitching while eating food. Most rodents have a long intestine with a cecum. Rodents lead a tree way of life (sony, flying squirrel, squirrel), as well as semi-aquatic (muskrats, nutria, beavers) and semi-underground (gophers, rats, mice). These are prolific animals. For most of them, the cubs are born blind and naked. Usually this happens in nests, hollows and burrows.

Lace-shaped

This detachment unites various types of rabbits, rabbits, as well as food - animals, similar in many respects to rodents. The main distinctive feature of the lagiformes is a specific dental system. They have 2 small incisors behind 2 large upper ones. Hares (a hare, a white horse) eat bark of bushes and young trees, grass. They go out to feed in the twilight and at night. The young at them are born sighted, with a dense wool. Unlike rabbits, rabbits dig deep holes. The female before birth of naked and blind cubs makes a nest of fluff, which she pulls out of her chest, and also from dry grass.

Predatory

Representatives of this detachment (bears, ermines, martens, lynxes, arctic foxes, foxes, wolves) usually feed on birds and other animals. The predator mammal actively pursues its prey. The teeth of these animals are divided into incisors, molars and fangs. The most developed are canines, as well as 4 molars. The representatives of this detachment have a short intestine. This is due to the fact that the predatory mammal eats easily digestible and high-calorie food.

Pinnipeds

We now turn to the consideration of pinnipeds. Their representatives (walruses, seals) are large carnivorous marine mammals. Rare coarse hair covered the body of most of them. The limbs of these animals are modified into fins. A thick layer of fat is deposited under their skin. Nostrils open only at the time of inspiration and expiration. When diving, the ear holes close.

Cetaceans

Real marine mammals - whales and dolphins - are included in this unit. Their body is fish-shaped. These marine mammals, for the most part, do not have hair on their bodies - they are preserved only near the mouth. In fins the forelimbs have been transformed, and the hind legs are absent. In the movement of cetaceans, a powerful tail has a great significance, which ends with a caudal fin. It is not true to say that marine mammals are fish. These are animals, although outwardly they resemble fish. Representatives of cetaceans are the largest mammals. The blue whale reaches a length of 30 meters.

Artiodactyls

This unit includes medium-sized and large omnivores and herbivores. Their feet have 2 or 4 fingers, most of them covered with hoofs. According to the peculiarities of the structure of the stomach and the methods of feeding, they are divided into non-ruminants and ruminants. In the latter (sheep, goats, deer) the incisors are only on the lower jaw, and the molars have a broad chewing surface. The non-ruminant have a single-chamber stomach, and the teeth are divided into radical, fangs and incisors.

Unchipped monkeys

We will continue to describe the orders of mammals. Unchipped-footed animals are such animals as horses, zebras, donkeys, tapirs, rhinoceroses. On the feet, most of them have a developed finger, on which there are massive hooves. Today, only Przewalski's horse survived from the wild horses .

Primates

These are the most highly developed mammals. The squad includes semi-monkeys and monkeys. At them grasping five-fingered finitenesses, thus the big finger of a brush is contrasted by the others. Almost all primates have a tail. The vast majority of them live in the subtropics and tropics. They inhabit mainly forests where they live in small family groups or herds.

Mammals, birds, reptiles, amphibians - all of them can be described for a very long time. We only briefly described the animals, described the existing detachments. The family of mammals is diverse and numerous, as you have just seen. I hope it was useful to you.