Beasts or mammals are the most highly organized vertebrates. A developed nervous system, breastfeeding of young, live birth, warm-bloodedness allowed them to spread widely throughout the planet and occupy a wide variety of habitats. Mammals are animals that live in forests (boars, elks, hares, foxes, wolves), mountains (rams, mountain goats), steppes and semi-deserts (jerboas, hamsters, ground squirrels, saigas), in the 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, more than 4 thousand species of animals are known to exist. Orders of mammals, as well as the characteristic features inherent in animals - we will talk about all this in this article. Let's start with a description of their structure.
Exterior structure
The body of these animals is covered with hair (even whales have its remains). There are coarse straight hair (awn) and thin sinuous (undercoat). The undercoat protects the awn from pollution and matting. The coat of mammals can only consist offrom the awn (for example, in deer) or from the undercoat (as in moles). These animals molt periodically. In mammals, this changes the density of the fur, and sometimes the color. In the skin of animals there are hair follicles, sweat and sebaceous glands and their modifications (mammary and odorous glands), horny scales (as on the tail of beavers and rats), as well as other horny formations found on the skin (horns, hooves, nails, claws). Considering the structure of mammals, we note that their legs are located under the body and provide these animals with more perfect movement.
Skeleton
In the skull they have a highly developed brain box. In mammals, teeth are located in the cells of the jaws. Usually they are divided into molars, canines and incisors. The cervical spine in almost all animals consists of seven vertebrae. They are movably connected to each other, except for the sacral and two caudal, which, growing together, form the sacrum - a single bone. The ribs articulate with the thoracic vertebrae, which are usually from 12 to 15. In most mammals, the forelimb belt is formed by paired shoulder blades and clavicles. Only a small part of the animals preserved crow bones. The pelvis consists of two pelvic bones fused with the sacrum. The skeleton of the limbs is from the same bones and sections as those of other representatives of the four-legged vertebrates.
What are the sense organs of mammals?
Mammals are animals that have auricles that help to capture odors, as well as determine their direction. Their eyes have eyelids and eyelashes. On the limbs, belly, headvibrissae are located - long coarse hair. With their help, animals feel even the slightest touch to objects.
The origin of mammals
Like birds, mammals are descendants of ancient reptiles. This is evidenced by the similarity of modern animals with modern reptiles. In particular, it manifests itself in the early stages of embryonic development. Even more signs of similarity were found in them with the animal-toothed lizards, which became extinct many years ago. Also for kinship with reptiles is the fact that there are animals that lay eggs containing many nutrients. Some of these beasts have cesspools, developed crow bones, and other signs of low organization. We are talking about the first animals (oviparous). Let's talk about them in more detail.
First Revealed
This is a subclass of the most primitive mammals alive today. Together with the signs already mentioned, it should be noted that they do not have a constant body temperature. The mammary glands of the first animals do not have nipples. Egg hatchlings lick milk off their mother's fur.
In this subclass, one detachment stands out - Single Passers. It includes 2 species: echidna and platypus. These animals today can be found in Australia, as well as on the islands adjacent to it. The platypus is a medium-sized animal. He prefers to settle along the banks of rivers and leads a semi-aquatic lifestyle here. In a hole dug by him in a steep bank, he spends most of his time. In the spring, the female platypus lays eggs (there are usually two of them) in a special hole,equipped nesting chamber. Echidnas are burrowing animals. Their body is covered with hard wool and needles. The females of these animals lay one egg, which they place in a bag - a fold of skin located on the abdomen. The hatchling from it remains in the bag until needles appear on its body.
Marsupials
Marsupials squad includes animals that give birth to underdeveloped cubs, after which they carry them in a special bag. They have a poorly developed or not formed placenta. Marsupials are distributed mainly in Australia, as well as on the islands adjacent to it. The most famous of them are the marsupial bear (koala) and the gigantic kangaroo.
Insectivores
Insectivores are a detachment that unites ancient placental primitive animals: hedgehogs, shrews, moles, desmans. Their muzzle is elongated, there is an elongated proboscis. Insectivores have small teeth and five-toed feet. Many of them have odorous glands near the root of the tail or on the sides of the body.
Shrews are the smallest representatives of insectivores. They live in meadows, shrubs, dense forests. These animals are voracious and attack small animals. In winter, they make tunnels under the snow and find insects.
Moles are animals that lead an underground lifestyle. They dig numerous holes with their front legs. The eyes of the mole are poorly developed and are black dots. The auricles are in their infancy. The short, dense coat has no definite direction and lies close when moving towardsbody. Moles are active all year round.
Baptera
The order Bats or Chiroptera includes animals of medium and small sizes that are capable of long-term flight. They are especially numerous in the subtropics and tropics. The teeth of these animals are of the insectivorous type. The most common in our country are earflaps, leather, evening wear. Representatives of bats settle in the attics of houses, in hollows of trees, in caves. During the day, they prefer to sleep in their shelters, and at dusk they go out to catch insects.
Rodents
This detachment unites a third of the mammal species that inhabit our planet today. These include squirrels, ground squirrels, rats, mice and other animals of medium and small size. Rodents are mostly herbivores. They have strongly developed incisors (two in each jaw), molars with a flat chewing surface. Rodent incisors have no roots. They are constantly growing, self-sharpening and wear down when eating food. Most rodents have a long intestine with a caecum. Rodents lead an arboreal lifestyle (dormouse, flying squirrels, squirrels), as well as semi-aquatic (muskrats, nutrias, beavers) and semi-underground (ground squirrels, rats, mice). They are fertile animals. Most of them cubs are born blind and naked. It usually occurs in nests, hollows and burrows.
Lagomorphs
This detachment unites various types of hares, rabbits, and pikas - animals that are similar in many respects to rodents. The main distinguishing feature of lagomorphs isspecific dental system. They have 2 small incisors behind the 2 large upper ones. Hares (hare, hare) feed on the bark of shrubs and young trees, grass. They come out to feed at dusk and at night. Their cubs are born sighted, with thick hair. Unlike hares, rabbits dig deep holes. The female, before giving birth to naked and blind cubs, makes a nest from fluff, which she pulls out of her chest, as well as from dry grass.
Predatory
Representatives of this order (bears, ermines, martens, lynxes, arctic foxes, foxes, wolves) usually feed on birds and other animals. The predatory mammal actively pursues its prey. The teeth of these animals are divided into incisors, molars and canines. The most developed are fangs, as well as 4 molars. 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
Let's move on to the consideration of pinnipeds. Their representatives (walruses, seals) are large predatory marine mammals. The body of most of them is covered with sparse coarse hair. The limbs of these animals are modified into flippers. A thick layer of fat is deposited under their skin. The nostrils open only for the time of inhalation and exhalation. When diving, the ear holes close.
Cetaceans
Real marine mammals - whales and dolphins - are part of this order. 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. The forelimbs were transformed into flippers, while the hind limbs are absent. In the movement of cetaceans, a powerful tail, which ends in a caudal fin, is of great importance. It is incorrect 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 squad includes medium-sized and large omnivores and herbivores. Their legs have 2 or 4 fingers, most of them are covered with hooves. According to the peculiarities of the structure of the stomach and methods of nutrition, they are divided into non-ruminant and ruminant. The latter (sheep, goats, deer) have incisors only on the lower jaw, and the molars have a wide chewing surface. Non-ruminants have a single-chamber stomach, and the teeth are divided into molars, canines and incisors.
Odd-toed ungulates
Let's continue to describe orders of mammals. Odd-toed ungulates are such animals as horses, zebras, donkeys, tapirs, rhinos. On their feet, most of them have a developed toe, on which there are massive hooves. Today, of the wild horses, only the Przewalski's horse has survived.
Primates
These are the most highly developed mammals. The order includes half-monkeys and monkeys. They have grasping five-fingered limbs, while the thumb of the hand is opposed to the rest. Almost all primates have a tail. The vast majority of them live in the subtropics and tropics. They inhabit mainly forests where they livesmall family groups or herds.
Mammals, birds, reptiles, amphibians - all of them can be described for a very long time. We only briefly characterized the animals, described the existing detachments that make up such a large "family". Mammals is a Class of Animals which is very varied and numerous, as you have just seen. We hope you found it useful.
