Which has about 4,500 species. Mammals live in all natural environments of the Earth: water, land, soil. Origin of mammals traces its history back to animal-like reptiles that lived in the Upper Carboniferous. The heyday of mammals occurred in the Cenozoic era.

So to basic characteristics of mammals the following can be attributed:

1. The body is divided into the trunk, neck, head, paired forelimbs, paired hind limbs and tail. The limbs are located under the body, so that the body does not come into contact with the ground during movement. Thanks to this, most mammals can move at fairly high speeds.
2. Skin in mammals quite thick, strewn with a variety of glands: sweat, sebaceous, odorous, milk. Also the skin has hairline , which is a temperature regulator.
3. Mammalian musculature is a complex differentiated system in which it is possible to distinguish aperture- thoraco-abdominal muscular septum. Is well developed subcutaneous muscles which provides facial expressions. Mammals move in a variety of ways: walking, running, climbing, jumping, flying, swimming.
4. The respiratory organs are lungs, which have a very large respiratory surface and alveolar structure. The respiratory process involves not only the lungs, but also intercostal muscles, as well as the diaphragm. Mammals are warm-blooded animals with a constant body temperature. This is due to a high level of vital activity, which produces a large number of heat.
5. Mammal heart- four-chambered, like in birds. There is a left aortic arch and is present complete blood separation- the tissues and organs of the body of mammals are fed with pure arterial blood. The spongy substance of bones, which contain red bone marrow- one of the most important hematopoietic organs.
6. Digestive system mammals is also not very simple. It has well differentiated sections, glands and organs. Saliva contains digestive enzymes. There are well-developed teeth that grow in sockets on the jaw bones and come in different types: molars, canines and incisors. Cloaca absent in most species, although herbivores have a well-developed cecum.
7. Mammalian excretory organs are paired pelvic kidneys, which filter the blood from protein breakdown products and other harmful substances. Urine descends through the ureters into bladder, and from there it is discharged out through the urethra ( urethra).
8. Brain section of the skull of mammals significantly more than in reptiles. There is a spine, which consists of 5 sections. A constant feature for all species is 7 vertebrae in the cervical region.
9. Mammalian brain is divided into 5 departments. The largest are the cerebral hemispheres of the forebrain of mammals, which have a cortex. Bark many species have convolutions. The cerebellum is also well developed. Mammalian cerebral cortex- is a separate important organ of the central nervous system, which controls the functioning of other parts of the brain and many systems of organisms. Have complex behaviors.
10. Organs of vision, hearing, smell, touch and taste very sensitive, thanks to them mammals orient themselves in space.
11. Mammals are strict dioecious animals who have internal fertilization. The embryo, after fertilization, usually develops in the uterus until birth. Gas exchange and nutrition of the embryo occurs through the placenta. After birth, the cubs are fed milk by their mothers.

The most successful group in the animal kingdom are mammals. In this article we will briefly talk about the characteristics of these animals, clarify which orders belong to mammals, and determine their habitats.

Features of mammals

This class of vertebrates belongs to the superclass of tetrapods, in which there are about 5.5 thousand species, including Homo sapiens. The main feature of the representatives of the “Mammals” group is feeding their young with milk.
In addition, there are the following signs:

• warm-blooded;
• live birth;
• the body is covered with hair, sweat and sebaceous glands, and horny formations are developed;
• the skull has a zygomatic arch;
• the spine is clearly divided into five sections;
• vertebrae of platycelial type;
• the subcutaneous muscles are highly developed, there is a diaphragm;
• highly developed nervous system, which allows you to quickly respond to stimuli from external environment;
• special structure of the hearing organ;
• the lungs have an alveolar structure;
• the heart is four chambered, the blood circulation is divided into two circles;
• unique structure of jaws and teeth.

The physiology of mammals is not particularly different from other four-legged representatives, but due to the high development of certain organ systems, this class is considered the highest highly organized among animals.

The Latin name of this class is Mammalia, which is derived from the Latin “mamma” – breast, udder. Russian word“mammals” means milk-feeding.

Spreading

Representatives of the class can be found everywhere. The only places where there are no mammals are the deep ocean and Antarctica, although seals and whales can be found off its coast.

Many subtypes are limited in distribution due to their attachment to environmental conditions. For many animals, temperature, soil and orographic conditions, as well as the availability of food are important.

The separate class “Mammals” was first described by Carl Linnaeus in 1758. At that time, there were 184 species; in modern times, all species are divided into 26-29 orders, which consist of 153 families, divided into 1229 genera.

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According to the traditional classification, this class of vertebrates is divided into the subclasses “Primal Beasts” (Prototheria) and “Beasts” (Theria). The latter, in turn, are divided into two infraclasses: Marsupials and Placentals.

Rice. 1. Classification.

Description of orders of mammals

All representatives of the class are quite diverse in appearance. The traditional body structure, which consists of a head, neck, torso, two pairs of limbs and a tail, varies in the ratio of shapes and sizes. So, a striking example of such variations can be Long neck giraffe, and whales lacking necks.

Rice. 2. External structure.

The order Chiroptera is very different from other mammals due to the transformation of the forelimbs into wings. Due to this, in the popular classification, bats were classified as birds.

The record holders for body size and weight are: the dwarf shrew (weight up to 1.7 g, length up to 4.5 cm), savannah elephant(weight - up to 5 tons, height at the shoulders up to 4 m), blue whale (length - 33 m, weight - up to 1.5 tons).

The list of mammals in Russia includes about 300 species. You can see their list in the following table:

Rice. 3. Diversity of mammals.

What have we learned?

The most highly developed group of animals are mammals. Representatives of this class can be found everywhere. They gained a leading position due to a number of their physiological and external features. Their main characteristics are feeding their offspring with milk, as well as being warm-blooded.

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Class Mammals (Mammalia) is the highest class of vertebrates, crowning the entire system of the animal world. The most important features of the general organization of mammals are:

· a high level of development of the nervous system, providing complex and perfect forms of adaptive response to environmental influences and a coherent system of interaction between various organs of the body;

· viviparity, combined (unlike other viviparous vertebrates, such as fish and reptiles) with feeding the young with milk. It ensures better safety of young animals and the possibility of reproduction in a very diverse environment;

· a perfect heat regulation system, thanks to which the body has a relatively constant temperature, i.e. constancy of the internal environment of the body. It is easy to imagine the enormous significance this has for the distribution of mammals in a variety of living conditions.

All this contributes to the almost universal distribution of mammals across the Earth, in which they inhabit all living environments: air-ground, water and soil-ground. The following can be noted in the structure of mammals. Their body is covered with hair or wool (there are rare exceptions of a secondary nature). The skin is rich in glands that have diverse and very important functional significance. Particularly characteristic are the mammary (mammary) glands, which are not even hinted at in other vertebrates. The lower jaw consists of only one (dentary) bone. In the middle ear cavity there are three (and not one, as in amphibians, reptiles and birds) auditory ossicles: the malleus, the incus and the stapes. The teeth are differentiated into incisors, canines and molars; sit in the alveoli. The heart, like that of birds, is four-chambered, with one (left) aortic arch. Red blood cells are without nuclei, which increases their oxygen capacity.

There are about 4,500 species of living mammals. Modern science about mammals involves not only knowledge of the patterns of their organization and life activity, but also the study of the biological foundations of fauna management. The appearance of mammals is diverse. This is explained by the amazing diversity of their living environment - ground surface, tree crowns, soil, water, air. The body sizes of mammals also vary greatly: from 2 cm with a mass of 1.5 g in the pygmy shrew to 30 m and even more with a mass of about 150 tons. blue whale, which corresponds to the mass of 30 elephants or 150 bulls. The skin, like that of other vertebrates, consists of two layers: the outer - epidermis and the inner - cutis, or the skin itself. The epidermis, in turn, is divided into two layers: the deep, germinal (otherwise known as malpighian), consisting of living, dividing cells, and the outer, represented by cells that gradually die off due to horny degeneration. The most superficially located cells become completely keratinized and slough off in the form of small dandruff or whole flaps (in some seals). Due to the activity of the epidermis in mammals, such derivatives as hair, nails, claws, hooves, antlers (except for deer), horny scales and skin glands arise. The skin itself is highly developed and consists mainly of fibrous tissue. The lower part of this layer is loose, and fat is deposited in it - this is the so-called subcutaneous fatty tissue. The skin itself is especially strongly developed in aquatic animals - seals and whales, in which it plays a thermal insulating role and reduces body density. The overall thickness of the skin varies among different mammal species. As a rule, terrestrial inhabitants of cold countries with luxuriant hair have less hair. There is also a difference in the strength of the leather. A kind of cutaneous tail autotomy occurs in mice, jerboas, and especially in dormouse. Their skin caudal sheath easily breaks off and slides off the caudal vertebrae, which allows the animal grabbed by the tail to escape from the enemy. The same biological significance The skin of hares is also very thin, fragile and poor in blood vessels. The skin of mammals has significant thermoregulatory significance. The role of the fur is clear, but it is also necessary to point out the importance of the skin blood vessels. With the expansion of their lumens, which are regulated by neuroreflex mechanisms, heat transfer increases sharply. In some species of mammals, the evaporation of sweat secreted by the glands of the same name from the surface of the skin is also essential. Skin glands in mammals, unlike reptiles and birds, are abundant and diverse. Sweat glands are tubular, their deep parts look like a ball. These glands secrete mainly water in which urea and salts are dissolved. Not all mammalian species have the same development of sweat glands. There are few of them in dogs and cats; many rodents have them only on their paws, groin area and lips. There are no sweat glands at all in cetaceans, lizards and some others. The sebaceous glands are grape-shaped, and their ducts open into the hair follicle. The secretion of these glands lubricates the surface of the epidermis and hair, protecting it from wear and wetting. In addition, secretions of the sebaceous and sweat glands give the animal and its tracks a specific odor and thereby facilitate communication between individuals of the same species and between different species. The odorant glands of mammals are a modification of the sebaceous or sweat glands, and sometimes a combination of both. The significance of the glands is varied. Their secretions help to recognize individuals of different sexes, serve to mark occupied territory, promote sexual arousal, and serve as a means of protection from enemies. These are the musk glands of musk deer, muskrats, shrews, muskrats, the anal glands of carnivores, the ungulate and horn glands of goats, chamois and other artiodactyls. The anal glands of the skunk are well known, the secretion of which is extremely caustic and serves to protect against enemies. The mammary glands arose as a modification of the sweat glands. In lower monotreme mammals, they retain a simple tubular structure, and their ducts open on a certain area of ​​the skin of the abdominal surface. In this case there are no nipples. In marsupials and placentals, the mammary glands are cluster-shaped, and their ducts open on the nipples. The location of the glands and nipples varies. U bats and in monkeys they are located on the chest, and there is one pair of nipples. In most ungulates, the nipples, like the glands themselves, are located in the groin area. In other animals, the mammary glands and nipples are located on the belly and chest. The number of nipples is to a certain extent related to the fertility of the species. The maximum number of them is 24 (possums from marsupials, tenrecs from insectivores).

Hair is the most characteristic epidermal formation of mammals. Its absence in some species (for example, cetaceans) is a secondary phenomenon. Although hair is a derivative of the epidermis, during development its rudiment - the hair follicle - penetrates deeply into the thickness of the skin itself, forming a hair follicle. The corium papilla with blood vessels and nerves protrudes into the bottom of the hair follicle. This is the so-called hair papilla. The formation and growth of hair occurs due to the reproduction and modification of cells of the bulb, and the hair shaft is already a dead formation, incapable of growth. There are three layers in the hair shaft: the outer skin, the cortex and the core. The top two layers consist of flat keratinized cells and, as a rule, contain a coloring pigment. The core consists of dried cells filled with air, which gives the wool low thermal conductivity. The hairline of mammals consists of different types of hair. Their main categories will be downy hair, awn and sensory hair, or vibrissae. In most species, downy hairs develop predominantly, forming the undercoat, or down. However, in some animals, such as deer, wild boars, and many seals, the undercoat is reduced, and the hair coat consists mainly of awns. On the contrary, underground mammals (mole, mole rat, zokor, etc.) have almost no guard hairs. In most species, the hair on the surface of the skin is distributed unevenly, collected in tufts consisting of guard hairs, around which there are several downy hairs (from two to two hundred). There is a periodic change of hair coat, or molting. In some species it occurs twice a year - in autumn and spring; such are squirrels, some hares, arctic foxes, and foxes. Moles also have a third, summer moult. Gophers and marmots molt once a year, in spring and summer. In northern mammals, the thickness of their fur changes with the seasons, and in some, their color. So, a squirrel has an average of 4200 hairs per 1 cm2 on its rump in summer, and 8100 in winter. For the winter, ermines, weasels, arctic foxes, white hares and some others turn white. A special category of hair is represented by vibrissae - very long, coarse hair that performs a tactile function. They are located on the head, lower part of the neck, chest, and in some climbers (for example, squirrels) - on the belly. Modifications of hair are bristles and needles.

In addition to hair, there are horny scales on the skin of mammals. They are most strongly developed in lizards. Horny scales are also observed on the paws (mouse-like rodents) and on the tail (mouse-like rodents, beavers, muskrats, and some marsupials). The horny formations will be the hollow horns of ungulates, nails, claws, and hooves. Deer antlers are also skin appendages, but they develop from the cutis and consist of bone material.

The muscular system of mammals is highly differentiated due to the variety of body movements. There is a diaphragm - a dome-shaped muscle that separates the abdominal cavity from the chest cavity and has important during ventilation of the lungs. The subcutaneous muscles are well developed. In hedgehogs, lizards and some armadillos, it ensures the body curls into a ball. The same muscles determine the bristling of animals, the raising of quills in hedgehogs and porcupines, and the movement of whiskers. On the face these are facial muscles.

The skull is characterized by a relatively large braincase, which is naturally associated with a large brain volume. The bones of the skull in mammals fuse late, allowing the brain to grow larger as the animal grows. Characteristic is the fusion of a number of bones into complexes. Thus, the four occipital bones form one; fusion of the ear bones leads to the formation of a single petrous bone; The temporal and sphenoid bones have a complex origin. Specific feature is the structure of the lower jaw, consisting only of the dentary bone. The angular bone gives rise to the tympanic bone, characteristic only of mammals, located in the form of an ovoid swelling at the bottom of the brain part of the skull. The articular bone, which in reptiles was also part of the lower jaw, turns into one of the auditory ossicles of the middle ear - the malleus. The lower jaw is attached to the skull (to the temporal bone) directly, since the quadrate bone, to which the lower jaw is attached in reptiles and birds, has also been modified into the auditory ossicle - the anvil. The structure of the spinal column in mammals is characterized by flat articulating surfaces of the vertebrae and a clearly defined division of the spine into sections: cervical, thoracic, lumbar, sacral and caudal. First two cervical vertebrae transformed into the atlas and epistropheus, and the total number of cervical vertebrae is seven. Thus, the length of the neck in mammals, unlike birds, is determined not by the number of vertebrae, but by their length. The only exceptions are sloths and manatees, in which the number of cervical vertebrae varies from six to ten. There are two true sacral vertebrae, but usually two more caudal vertebrae are fused to them. The basis of the shoulder girdle is the scapula, to which a rudimentary coracoid grows, and only in monotremes the coracoid is represented by an independent bone. The clavicle is present in species whose forelimbs move in different planes, such as monkeys. Species that move these limbs in one plane, such as ungulates, do not have clavicles. The limbs of mammals are quite typical of terrestrial vertebrates, but the number of fingers varies from five to one. A reduction in the number of fingers or rudimentation of the outermost ones is observed in fast running species, such as ungulates and jerboas. Relatively slow-moving animals, such as bears and monkeys, rely on their entire palm and foot when walking (plantigrade species); fast runners, such as dogs, ungulates, rely only on their fingers (digitate species). The digestive tract is characterized by a large length and well-defined division into sections. It begins with the vestibule of the mouth, located between the fleshy lips (characteristic only of mammals) and the jaws. In some animals, expansion of the vestibule leads to the formation of large cheek pouches (hamsters, chipmunks, ground squirrels, and some monkeys). Monotremes and cetaceans do not have fleshy lips. The ducts of the salivary glands open into the oral cavity, the secretion of which not only moistens food, but also chemically acts (the enzyme ptyalin) on starch, converting it into sugar. The saliva of desmodes that feed on blood has an anticoagulant property, i.e. prevents blood clotting. In some insectivores, saliva is poisonous and is used to kill prey. The teeth of mammals are differentiated into groups, depending on the type of food. Weak differentiation is characteristic of poorly specialized insectivores (shrews). In toothed whales, differentiation of teeth disappeared for the second time. The stomach, which has numerous glands, has different volumes and internal structure. The stomach of ruminant ungulates is the most complex, absorbing a huge mass of low-calorie and indigestible feed. Lizards and anteaters have no teeth, and the stomach, like that of birds, consists of two sections: glandular and muscular. The similarity is strengthened by the fact that in the second, deliberately swallowed pebbles are found, which ensure the grinding of food. In addition to the small, large and rectal sections of the intestine, some mammals also have a blind section, in which food is subjected to bacterial fermentation. The cecum is especially strongly developed in those feeding on rough plant foods; its length reaches a third of the length of the intestine. The ducts of the liver and pancreas empty into the anterior part of the small intestines. The lungs have a complex cellular structure. The smallest pulmonary passages - bronchioles - end in vesicles - alveoli, in the walls of which the thinnest blood vessels branch. The number of alveoli even in sedentary animals (for example, sloths) is 6 million, and in very active carnivores it reaches 300–500 million. The breathing mechanism is determined by a change in the volume of the chest as a result of the movement of the intercostal muscles and the diaphragm. The number of respiratory movements in mammals depends on the size of the animal, which determines the different metabolic rates. It is (per 1 minute): for a horse – 8–16, for a black bear – 15–25, for a fox – 25–40, for a rat – 100–150, for a mouse – about 200. Ventilation of the lungs not only ensures gas exchange, but it also has thermoregulatory significance. As the temperature rises, the number of respirations increases, and at the same time the amount of heat removed from the body also increases. Thus, in a dog, the ratio of heat transfer during breathing to the total heat loss at an air temperature of 8 ° C is (in percent) 14, at 15 ° C - 22, at 30 ° C - 46. Circulatory system mammals are similar to those of birds. The heart is completely divided into two atria and two ventricles; One aortic arch departs from the left ventricle (but not the right one, like in birds, but the left one). The aortic arch sends the carotid arteries to the head and, bending around the heart, stretches under the spinal column, along the way directing branched vessels to the organ systems. The venous system is characterized by the absence of portal circulation in the kidneys, which is well developed in the liver, as in other vertebrates. The liver neutralizes toxic products of protein metabolism. The size of the heart varies depending on the size of the body, lifestyle, and ultimately due to the intensity of metabolism. The weight of the heart, expressed as a percentage of the total body weight, is: in toothless whales –0.6–1.0, in a wild rabbit –3.0, in a mole –6.0–7.0, in bats –9, 0–15.0. All these features provide mammals with a higher level of metabolism and general vital activity.

Mammals are distributed almost throughout our planet, they are not found only on Antarctic continent, although seals and whales are also known to be mammals off its coast. Polar bears, pinnipeds, and cetaceans (narwhals) live in the North Pole region.

Mammals are a class of vertebrates. The first mammals descended from mammal-toothed reptiles (theriodonts) in the Triassic, reaching their greatest diversity in the Oligocene. Mammals are characterized by mammary glands that produce milk for feeding their young, hair, a more or less constant body temperature (on average about 30 °C), pulmonary respiration, and a 4-chambered heart. Mammals include proto-beasts, or cloacals (order 1 - monotremes), and viviparous animals (marsupials and placentals).

Mammals are widely distributed in their living environments. Along with terrestrial species, which are the majority, a number of species are more or less associated with the aquatic environment; many actively fly through the air; In addition, a significant number of animals live in the soil, where all or most of their lives pass.

No class of vertebrates has produced such a wide variety of forms as mammals, often completely different from each other.

The class of mammals includes 20 modern orders and 12-14 extinct ones. Mammals (order primates) also include humans or hominids. Mammals approx. 4000 species; warm-bloodedness, care for offspring, high organization of the nervous system allowed mammals to populate all areas of the earth from the North. poles to the shores of Antarctica. Many mammals are hunted; some are the ancestors of farm animals. Mammals (sometimes only carnivores) are also called animals.

The branch of zoology that studies mammals is called teriology. The numbers and ranges of many mammals are declining: 230 species and 91 subspecies are on the Red List of the International Union for Conservation of Nature and Natural Resources.

The fauna, being an integral part of the natural environment, acts as an integral link in the chain of ecological systems, a necessary component in the process of the cycle of matter and energy of nature, actively influencing the functioning of natural communities, the structure and natural fertility of soils, the formation of vegetation, the biological properties of water and the quality of the environment as a whole. At the same time, the animal world is of great economic importance as a source of food products, industrial, technical, medicinal raw materials and other material assets and therefore acts as natural resource for hunting, whaling, fishing and other types of fishing. Certain species of animals have great cultural, scientific, aesthetic, educational, and medicinal significance.

PRIMARY BEASTS (cloacae)- a subclass of the most primitive modern mammals. The only order is monotremes. MONTREME (oviparous)- the only detachment of the subclass of primal beasts. They have retained a number of archaic features inherited from reptiles - laying eggs, etc. The mammary glands are primitive and similar to the sweat glands. The intestines, reproductive ducts and bladder open into the cloaca (hence the name - monotreme). 2 families: echidnas and platypuses; 3 types.

HOMINIDS(from Latin homo - man) - a family of the order of primates. Includes a person modern type(Homo sapiens) and fossil people: Pithecanthropus, Neanderthals and, probably, some fossil higher primates such as Australopithecus.

In the photo there is a kitten in flowers(I really love beautiful photos of animals - I collect them and, whenever possible, post them here on the site).

Forests, steppes

Some animals live in very diverse environments. Common fox distributed in forests, steppes, deserts and mountainous areas. Wolves live in even more diverse conditions (in addition to the indicated zones for foxes, wolves are also found in the tundra). Such animals do not have clearly defined adaptations to life in any particular environment.

The specific habitat determines many of the characteristics of animals. Among the inhabitants tropical forests stand out, for example, are South American sloths, spider monkeys, and some South Asian bears, whose entire or almost entire life is spent in the crowns of trees. Here they feed, rest and reproduce. In connection with this way of life, species of this group have developed various adaptations.

Bears and martens climb with sharp claws, lemurs and monkeys have grasping paws. Some South American monkeys, arboreal anteaters and opossums have developed prehensile tails. Finally, gibbon monkeys make jumps, first swinging pendulum-like on their forelimbs. A peculiar adaptation to passive gliding flight is developed in flying squirrels and South Asian woolly wings.

Among the inhabitants of the forests there are animals that lead a strictly terrestrial lifestyle (elk, true deer, roe deer, African okapi). The forest serves as shelter for them, and the branches and leaves of trees serve partly as food.

Animals of open spaces

Animals living in open spaces have different forms and degrees of specialization. Ungulates and some predators have relatively sharp eyesight; their fast running helps during long journeys in search of food and water, and during pursuit. The running speed of some animals is as follows (in km/h): bison - 40-45, giraffe - 45-50, wild ass - 50-55, zebra - 60-65, Thomson's gazelle - 75 - 80, and among carnivores : lion - 75-80, cheetah - 105-115. Ungulates do not make homes or temporary shelters and give birth to developed young on the surface of the earth, capable of moving with their mother in the first days.

Jumping

There are various types of jumping animals, which are found in various systematic groups and in different countries. These are the Asian desert jerboas (rodents), American kangaroo rats (rodents), African jumpers (insectivores), and Australian kangaroos (marsupials). Feature These animals have a “ricocheting” run: jumping forward and from side to side, as if bouncing due to uneven ground. The long tail plays the role of a balancer and rudder. They reach running speeds of up to 20 km/h. They differ significantly from the species of the previous group in that, in addition to kangaroos, they construct permanent shelters in the form of burrows. Newborns are all blind and naked.

"Gopher Type"

There is another type of animal in open spaces - the “gopher type”. These are small or medium-sized animals that inhabit steppes and mountain meadows with relatively dense grass, so they do not have the need, and at the same time, the ability to move quickly in search of food. They construct permanent burrows in which they breed and rest; In addition, they build temporary holes in which they only hide when in danger. These animals have a squat body, short legs, and run slowly. Due to the presence of burrows, they give birth to helpless, naked young. In addition to gophers, this group includes marmots, hamsters, and steppe species of pikas.

Underground

Underground beasts are highly specialized, relatively large group. There are representatives of it among different groups and in many countries. These are Eurasian and North American moles (insectivores), Eurasian mole rats and mole rats (rodents), African mole rats (rodents), and Australian marsupial moles. Their body is bar-shaped, without a clearly defined neck. The fur is low and velvety. The eyes are small, and in some they are hidden under the skin. There are no auricles. The tail is vestigial. The method of making underground passages varies among different species. Moles dig with large, outward-turned front paws, rotating around the axis of the body. Mole rats and mole rats have weak paws; they dig with the incisors of the lower jaw, and only throw out the earth with their paws. The system of burrows in these animals is very complex, but only a small part of them serves as the actual dwelling, and the rest are passages formed when searching for food.

Water

Aquatic animals have varying degrees of adaptation to life in water. One of the types of ferrets, the mink, always settles along the banks of reservoirs, where it makes burrows, but obtains food both in the water (fish, amphibians) and on land (small rodents). There are no significant changes in its organization compared to terrestrial ferrets. The river otter is more closely associated with water, foraging mainly in water (fish, amphibians); terrestrial rodents play a small role in its diet. It swims and dives well, and at the same time one can note such adaptive features as reduction of the ears, shortening of the limbs, and the presence of membranes between the fingers.

The sea otter, or sea otter, incorrectly called the sea beaver, lives in the northern part of the Pacific Ocean and feeds only in the sea (mainly sea ​​urchins). Animals come ashore to breed, sometimes to rest and during strong storms. The sea otter's limbs are like flippers, and all the fingers are united by a thick leathery membrane.

Semi-aquatic

Semi-aquatic rodents are well known: beaver, muskrat, nutria.

Pinnipeds are true aquatic animals, but they only breed outside aquatic environment- on the ice or on the shore.

Completely aquatic animals are cetaceans and sirenids, capable of reproducing in water. Their characteristics are given in the appropriate places in the volume. Here it is important to emphasize that among modern animals one can find a whole series of transitions from terrestrial, through semi-aquatic and semi-aquatic to completely aquatic forms.

Air

Finally, we must mention the species of mammals that move through the air. And in this case, it is possible to identify a number of animals from those jumping from tree to tree to those capable of active flight. In squirrels, to some extent, the role of a parachute, which determines the initial elements of gliding, is played by the body spread out during the jump with outstretched limbs and the pubescence of the tail combed in two. Flying squirrels and woolly wings are more specialized, having leathery folds between the front and hind legs; in the woolly wing, folds are also located between the hind legs and tail. Such a device not only allows you to glide when descending along a sloping line, but also serves for turns in the air and even for a slight rise. Flying squirrels can glide at a distance of 30-60 le, and woolly wings - at 130-140 m.

Among mammals, only chiropterans are capable of active flight (with the help of wings). They are described in detail in the relevant part of the volume. Here it is important to emphasize the amazing variety of adaptations of mammals to life in different environments and to different forms of behavior. All this undoubtedly expanded the possibility of their adaptive divergence, which led to an amazing diversity of animal forms.

Mammal Reproduction

Mammalian reproduction, characterized by great diversity, still has common features: internal fertilization, viviparity (with rare and incomplete exceptions), feeding newborns with milk, as well as the construction of special nests for childbirth in most types.

Monotremes

In the simplest case, in monotremes, there is no true viviparity and females lay eggs. However, they lay eggs after quite a long development in the female genital tract, and the duration of incubation of the eggs after their laying is less than half the period that passes from the time of their fertilization to laying. Thus, monotremes experience “premature” birth or incomplete ovoviviparity.

Marsupials

In marsupials, the gestation period is short and without the formation of a true placenta. Small marsupial species (such as opossums) carry their young for only 8–13 days, and newborns have a mass of only 0.003% of their mother's mass. For comparison, we point out that in hares the weight of a newborn is 3% of the mother’s weight. Underdeveloped marsupial cubs complete their development by being attached to the nipples, which often open into the cavity of the leathery bursa.

Placental

The duration of pregnancy, and in this regard the development of newborns, differs significantly among different species of placental animals. The minimum duration of pregnancy is typical for the gray hamster (11-13 days), the maximum for the Indian elephant (more than 500 days). The duration of intrauterine development depends on the combined effect of three circumstances.

Firstly, this is due to the size of the animal. Thus, a tiny bank vole (its body length is about 10 cm) carries cubs for only 18 days, a larger common gray vole (body length up to 13 cm) - 20 days, an even larger pasyuk rat - 22 days, a hamster (body length up to 35 cm) - 30 days, marmot boibak (body length up to 59 cm) - 40 days, fox (body length up to 90 cm) - 52 days.

Secondly, the conditions of childbirth, or more precisely, the conditions in which newborns find themselves, matter. All the mammals mentioned above give birth in securely constructed burrows, and their newborns are naked, blind, and helpless.

Wild rabbits also kitten in burrows; their pregnancy lasts only 30 days, and the young are just as blind and naked. Hares of similar size (small races of hare and sandhills), which do not make burrows or nests, carry for about 50 days, and they give birth to sighted hares, covered with hair and capable of running in the first days. Nutria, close in size to the marmot (body length up to 60 cm), gives birth to its young in a very primitively constructed burrow or in a ground nest. Her pregnancy is three times longer than that of a marmot (about 130 days), and the newborns are as well developed as those of hares.

Ungulates, mustelids

The duration of pregnancy is long in ungulates that do not have any shelters. In mountain sheep it reaches 150 days, in deer and elk - 240-250 days, in zebra - 340-365 days. Newborns in these species are well developed and can already follow their mothers in the first days after birth.

Thirdly, the duration of pregnancy depends on the duration of the interval between the fertilization of the egg and the attachment of the embryo to the wall of the uterus, i.e., the formation of the placenta. There are species in which this gap is very large, and it mainly affects the gestational age. Thus, in sable and marten, the beginning of egg development is interrupted by a resting phase, when development almost completely stops (latent phase of pregnancy). This period lasts several months, and as a result, in these relatively small animals (body length about 50 cm), giving birth in well-protected nests, pregnancy lasts for 230-280 days. In this case, the cubs are born blind and helpless.

The latent phase of pregnancy is also characteristic of other mustelids (ermine), as well as wolverine, badger, seals, roe deer, etc. It also happens that difficult pregnancy observed only in some individuals of this species. For example, in badgers that mate in autumn, pregnancy lasts 150 days, and in badgers that mate in summer, gestation lasts 220-240 days. In stoats, pregnancy usually lasts 300-320 days and most of this period falls in the latent phase. But there are cases when the latent phase almost or completely disappears and the period of intrauterine development lasts only 42-70 days.

Due to the conditions of childbirth, the varying duration of pregnancy and, mainly, the presence or absence of a latent phase, the timing of mating does not have the same uniformity as, for example, in birds. Wolves and foxes mate at the end of winter, ferrets and hares in the spring, sables and martens in the summer, and deer in the fall. But it is remarkable that the vast majority of births are timed to coincide with the most favorable time for raising young animals - the end of spring and the beginning of summer.

Reproduction rate and litter size

The reproduction rate of different species varies significantly. This difference is determined by three circumstances: the time of puberty, the length of the interval between births, and the number of cubs in the litter.

The variation in the rate of puberty is very large, as can be seen from the following examples. Bank voles reach sexual maturity at the age of about one month, muskrats - no earlier than three months, hares, foxes - about a year, sables, wolves - about two years, brown bears - about 3-4 years, walruses - at 3-6 years, bison - 5-6 years, elephants - 10-15 years, rhinoceroses - about 20 years. Thus, this indicator varies within several hundred times.

The frequency of births also varies greatly. Small rodents, such as the house mouse and the common vole, under favorable temperature and food conditions, can produce up to 6-8 litters during the year. Brown hares are breeding in the south all year round and bring up to 4 litters, white hares - up to 3 litters. Ferrets, martens, sables, foxes, wolves, deer and many others breed only once a year. Brown bears and camels give birth, as a rule, once every two years. Walruses, polar bears, tigers, some baleen whales, and bison usually give birth once every two to three years. This rate of reproduction varies tens of times.

The size of the brood also varies significantly, varying from 1 to 20 cubs, more often up to 12-15. The least fertile species are those that are characterized by constant and sometimes long-term movements and that do not even suit primitive temporary dwellings. These are elephants, horses, zebras, donkeys, llamas, camels, giraffes, deer, seals, whales, sirens.

The largest brood size is characteristic of small burrowing rodents: voles, mice, and some ground squirrels. It is not uncommon for these species to have 10 or more young. In some cases, even up to 20 embryos were noted. The fertility of some hares (up to 12 cubs), wild boars (up to 12) and burrowing predators of small and medium size (fox - up to 12, arctic fox - up to 18, ermine - up to 18) is significant. The large size of the brood in these species is ensured by the reliability of the dwellings in which newborns are sheltered, as well as by the abundance and availability of food (at least in some years).

An intermediate position is occupied by large predators and some large rodents. Lions, pumas, tigers, lynxes, and brown bears bring 2-3 cubs each.

It is more difficult for these animals to obtain food for their young than for the previous ones; most of them do not build reliable homes when raising their young.

Species that mature slowly have long intervals between births and smallest number cubs. On the contrary, species of mammals in which puberty occurs early breed frequently and have large broods.

The rate of reproduction is quite closely dependent on life expectancy: those who reproduce slowly live much longer than those who are highly fertile. The approximate life expectancy in a natural environment is as follows: Indian elephant - 70-80 years, bison - up to 50 years, red deer - up to 25 years, baleen whales - about 20 years, brown bear - 30-50 years, wolf - about 15 years, fox - 10-12 years, sable - 7-8 years, hares - 5-7 years, voles - 14-18 months. As a result, the rate of population renewal varies greatly among different species.

Adaptation to difficult climatic conditions and migration

The adaptations of mammals to surviving periods of the year that are unfavorable in terms of food and weather are more diverse and advanced than those of lower classes. By winter or dry summer, reserve energy substances accumulate in the body, helping to survive the difficult season. In addition to the accumulation of glycogen in the liver, many species become fatter to one degree or another. For example, the small gopher has a mass of about 100-150 g in the spring, and up to 400 g in mid-summer. In the bobak marmot, the subcutaneous and internal fat in June is 10-15 g, in July - 250-300 g, in August - 750 -800 g. In some individuals, up to 25% of the total body weight is fat.

Seasonal adaptations are also expressed in migrations. In autumn, as feeding conditions worsen, the bulk of arctic foxes and reindeer migrate from the tundra to the south, into the forest-tundra and even into the taiga, where it is easier to obtain food from under the snow. Following the deer they migrate south and tundra wolves. In the northern regions of the tundra, white hares undertake mass migrations to the south at the beginning of winter, and in the opposite direction in the spring. By summer, mountain ungulates rise to the upper belts of the mountains with their rich grass stand, but in winter, as the depth of the snow cover increases, they descend. And in this case, migrations of some predators, such as wolves, combined with ungulates are observed.

Regular seasonal migrations of desert ungulates also depend on seasonal changes in vegetation cover, and in some places, on the nature of the snow cover. In Kazakhstan, saigas often live in the northern clayey semi-desert steppes in the summer; in winter they migrate south, to the area of ​​less snowy wormwood-fescue and wormwood-hodgepodge semi-deserts.

Seasonal migrations are observed in bats, cetaceans and pinnipeds.

In general, migration is characteristic of a relatively smaller number of species among mammals than among birds and fish. They are most developed in sea animals, bats and ungulates, while among the species of the most numerous groups - rodents, insectivores and small predators - they are practically absent.

Scientific definition. Mammals- these are representatives of a monophyletic taxon of endothermic amniotes, which differ from reptiles in the presence of hair, three middle auditory ossicles, a mammary gland and a neocortex. The mammalian brain regulates body temperature and the cardiovascular system, including the four-chambered heart.

general information

Mammals are not the most numerous group, but they are surprisingly easy to adapt to environmental conditions. They live in a variety of natural environments. The brain volume of mammals is larger than that of representatives of other classes of animals. The largest land and sea animals are mammals - elephants on land and whales in the ocean.

There are about 4,500 species of mammals, including giant whales, tiny shrews, and the bats. The largest mammal in the world is, growing up to 30 meters in length and weighing up to 200 tons. The largest ungulates are the giraffe (height 5.5 meters, weight 1.5 tons) and the white rhinoceros (height 1.8 meters, weight more than two tons). The smartest animals are (starting with the smartest mammal): chimpanzee, gorilla, orangutan, baboon and dolphin.

What mammals lay eggs

Platypuses And echidnas They are the only mammals that lay eggs. These amazing animals live only in Australia, more precisely in its eastern part. Platypuses live in rivers and have webbed feet and a flat, paddle-like tail adapted for swimming. The female platypus lays one or two eggs in a burrow, and feeds the hatched offspring with milk. Female echidnas bury their eggs in a hole, but carry their young in a pouch - where they grow and feed, licking milk from her fur.

Are marsupials the only animals that live in Australia?

No, some species live in New Guinea and the Solomon Islands in Pacific Ocean, and two species, the American opossum and the Chilean opossum, live in Northern and South America respectively. Mammals that have a pouch for carrying their young are called marsupials. This order includes kangaroos, koalas, wallabies, opossums, wombats, and bandicoots.

How are mammals born?

Placental mammals (the largest group of mammals) give birth to live young. Inside the female's body, the developing embryo is nourished through a special organ called the placenta. Most mammalian babies go through all stages of development (except marsupials) by the time they are born, although they still require parental care after birth.

The largest group of mammals

Surprisingly, the largest group of mammals is bats. These are the only mammals that can fly and are represented by more than 970 species. Most bats are similar in size to the common mouse. The largest among bats are fruit bats And flying foxes. Many bats are nocturnal hunters of insects, rodents and frogs. To navigate well in space at night, bats use echolocation. They produce high-frequency squeaks that echo off nearby objects.

What animals are called carnivores?

For most animals, the most important activity is searching for food. Unlike plants, which need enough sunlight to produce their own food, animals must constantly search for food. Otherwise they simply will not survive. Different animals need different kinds food. Herbivores eat plants carnivores- other animals, and omnivores- both plants and animal meat.

Seals, dolphins and whales are marine mammals whose ancestors lived on land millions of years ago. Their apron limbs became pectoral fins, and their hind limbs became a tail with two horizontal blades. Seals and sea lions can move on land; whales and dolphins are only sea animals.

Leopards usually hunt at night. They drag their prey up a tree - away from other animals that feed on carrion, such as hyenas.

A baby kangaroo grows inside its mother's pouch. She protects him from danger until the bag becomes too small for the cub.

Many bats have large ears, which help them catch echoes. The bat pinpoints the location of its prey, e.g. moth. Bats roost for the night, hanging upside down and holding onto support with tenacious claws on their paws.