Animals or mammals are the most highly organized vertebrates. A well-developed nervous system, milk feeding of babies, 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 (wild boars, moose, 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 it is known that more than 4 thousand species of animals exist. Mammal units, 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.
External structure
The body of these animals is covered with wool (even whales have its remains). Distinguish between coarse straight hair (awn) and thin sinuous (undercoat). An awn protects the undercoat from contamination and stalling. The coat of mammals can consist only of awn (for example, in deer) or of undercoat (as in moles). These animals molt periodically. In mammals, the density of the fur, and sometimes the color, changes. 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 horn 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 jaw cells. Usually they are divided into molars, fangs and incisors. The cervical spine consists of almost all animals from seven vertebrae. They are movably connected to each other, except for the sacral and two caudal, which, when fused, form the sacrum - a single bone. The ribs articulate with the thoracic vertebrae, which are usually 12 to 15. In most mammals, the paired shoulder blades and clavicles form the forelimb belt. Only a small part of the animals preserved crow bones. The pelvis consists of two pelvic bones fused to the sacrum. The skeleton of the limbs is from the same bones and departments as other representatives of the four-legged vertebrates.
What are mammalian sensory organs?
Mammals are animals that have auricles that help capture odors and determine their direction. Their eyes have eyelids and eyelashes. On the limbs, abdomen, head are vibrissae - long stiff hair. Animals with their help feel even the slightest touch on 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 embryo development. An even greater number of signs of similarity were found in them with the beast-lizard dinosaurs, which died out many years ago. Also related to the reptile relationship is the fact that there are animals that lay eggs that contain a lot of nutrients. Some of these animals have cesspools, developed crow bones, and other signs of poor organization. It is about the first animals (ovipositors). We will tell you more about them.
First beasts
This is a subclass of the most primitive mammals living 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. Young hatching from eggs lick milk from the mother’s hair.
In this subclass, one detachment stands out - Single-pass. 2 species belong to it: echidna and platypus. These animals can be found today 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 the rivers and leads a semi-aquatic lifestyle here. In the hole he dug in a steep bank, he spends most of his time. In the spring, the female platypus lays eggs (there are usually two) in a special hole, equipped with a nesting chamber. Echidna - beasts digging. Their body is covered with stiff wool and needles. Females of these animals lay one egg, which they put in a bag - a fold of skin located on the stomach. The baby hatched from it is in the bag until needles appear on its body.
Marsupials
The order Marsupials includes animals that give birth to underdeveloped cubs, after which they are carried in a special bag. They have a poorly developed or not formed placenta. Marsupials are prevalent mainly in Australia, as well as on the islands adjacent to it. The most famous of them are marsupial bear (koala) and gigantic kangaroo.
Insectivores
Insectivores are a detachment that unites ancient placental primitive animals: hedgehogs, shrews, moles, muskrats. The muzzle is elongated, there is an elongated proboscis. Insectivores have small teeth, and their legs are five-fingered. 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 passages under the snow and find insects.
Moles are animals that lead an underground lifestyle. They dig numerous burrows with their front legs. The mole's eyes are poorly developed and are black dots. The auricles are in their infancy. Short thick coat does not have a specific direction and fits snugly when moving to the body. Moles are active year round.
Bats
The order Bats or Bats includes small and medium-sized animals that are capable of long flight. In the subtropics and tropics, they are especially numerous. The teeth of these animals are of an insectivorous type. The most common in our country are ear-flaps, leather, evening dresses. Representatives of bats live in the attics of houses, in hollows of trees, in caves. During the day, they prefer to sleep in their shelters, and at dusk go fishing for insects.
Rodents
This detachment unites one third of the species of mammals that inhabit our planet today. These include proteins, gophers, rats, mice and other animals of medium and small size. Most rodents are herbivorous animals. They have highly developed incisors (two in each jaw), molars, with a flat chewing surface. No rodent incisor roots. They constantly grow, self-sharpen and grind when eating food. Most rodents have a long intestine with a cecum. Rodents lead a tree-like lifestyle (dormouse, flying squirrels, squirrels), as well as semi-aquatic (muskrats, nutria, beavers) and semi-underground (gophers, rats, mice). These are prolific animals. In most of them, cubs are born blind and naked. This usually occurs in nests, hollows, and burrows.
Hare
This squad unites various species of hares, rabbits, as well as pikas - animals similar in many respects to rodents. The main distinguishing feature of rabbit-like is the specific dental system. They have 2 small incisors behind 2 large upper ones. Hares (grouse, white hare) feed on bark of shrubs and young trees, grass. They go feeding at dusk and at night. Cubs are born sighted, with thick hair. Unlike rabbits, rabbits dig deep holes. The female, before giving birth to naked and blind cubs, makes a nest of fluff, which she pulls out of her breast, 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 prey mammal actively pursues its prey. The teeth of these animals are divided into incisors, molars and fangs. 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 a predatory mammal eats easily digested and high-calorie foods.
Pinnipeds
We turn to the consideration of pinnipeds. Their representatives (walruses, seals) are large predatory marine mammals. Rare coarse hair covers the body of most of them. 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 duration of inspiration and exhalation. When diving, the ear holes are closed.
Cetaceans
Real marine mammals - whales and dolphins - are part of this squad. Their bodies are fish-shaped. Most of these marine mammals do not have hair on the body - they are preserved only near the mouth. The forelimbs were transformed into flippers, and the hind limbs were absent. In the movement of cetaceans, the powerful tail, which ends with the caudal fin, is of great importance. It is not true 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 omnivorous and herbivorous animals. Their legs have 2 or 4 fingers, most covered with hooves. According to the features of the structure of the stomach and methods of nutrition, they are divided into non-ruminant and ruminant. The latter (rams, goats, deer) have incisors only on the lower jaw, and molars have a wide chewing surface. The non-ruminant has a single-chamber stomach, and the teeth are divided into molars, canines and incisors.
Ungulate
We continue to describe the orders of mammals. Odd-headed animals are animals such as horses, zebras, donkeys, tapirs, and rhinos. On their feet, most of them have a developed toe, on which are massive hooves. Today, only Przhevalsky's horse has survived from wild horses .
Primates
These are the most highly developed mammals. The detachment includes half monkeys and monkeys. They have grasping five-fingered limbs, while the thumb is opposed to the rest. Almost all primates have a tail. The vast majority of them live in the subtropics and tropics. They mainly inhabit 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 units that make up such a large "family". Mammals are an Animal Class that is very diverse and numerous, as you have just seen. Acquaintance with him, we hope, was useful to you.