Their natural habitat. The buildings look like rock formations with numerous burrows and crevices. Therefore, bats can find shelter in basements and attics, foxes are able to dig a hole under a fence, raccoons like to settle in ventilation ducts (moreover, both foxes and raccoons look for food in garbage cans).

A golf course resembles a clearing in a forest, steppe or meadow. Here you can look for signs of the habitation of skunks, deer, moles and rabbits. There are usually not too many trees in the suburbs, but birdhouses and special houses for bats can be inhabited by forest inhabitants: flying squirrels, mice, bats.

Forests and groves

Forests once covered much of America east of the Appalachian Range, but by 1900 settlers had cleared as far as New England. The forests now growing on this land have recently been planted. Many mammals characteristic of these places depended on the composition forest species. Some disappeared completely, while others, such as bats, became much less common. Similar changes have taken place in Europe and Russia.

Seals, sea lions and walruses during the period of the appearance of offspring crawl out onto land, forming large colonies and returning every year to the same place. If you see them, then try not to disturb them. Seals sometimes come out on land and just to relax in the sun.

Many mammals are partially aquatic, living near lakes, streams, or ocean shorelines (eg seals, sea lions, walruses, otters, muskrats, and many others). Whales and dolphins () are completely aquatic and can be found in all and some rivers. Whales can be found in polar, temperate and tropical waters, both near shore and in the open ocean, and from the surface of the water to depths of more than 1 kilometer.

The habitat of mammals is also characterized by different climatic conditions. For example, the polar bear lives calmly at sub-zero temperatures, while lions and giraffes need a warm climate.

Mammal groups

Baby kangaroo in mother's pouch

There are three main groups of mammals, each of which is characterized by one of the main features of embryonic development.

  • Monotremes or oviparous (Monotremata) lay eggs, which is the most primitive reproductive feature in mammals.
  • marsupials (Metatheria) are characterized by the birth of underdeveloped young after a very short gestation period (8 to 43 days). Offspring are born at a relatively early stage of morphological development. The cubs are attached to the mother's nipple and sit in the bag, where their subsequent development takes place.
  • Placental (Placentalia) are characterized by long gestation (pregnancy), during which the embryo interacts with its mother through a complex embryonic organ - the placenta. After birth, all mammals depend on the milk of their mothers.

Lifespan

Just as mammals vary greatly in size, so does their lifespan. As a rule, small mammals live less than larger ones. Bats ( Chiroptera) are an exception to this rule - these relatively small animals can live for one or more decades in natural conditions, which is significantly longer than the lifespan of some larger mammals. Life expectancy ranges from 1 year or less to 70 years or more in the wild. Bowhead whales can live for over 200 years.

Behavior

The behavior of mammals varies significantly among species. Since mammals are warm-blooded animals, they require more energy than cold-blooded animals of the same size. Activity indicators of mammals reflect their high energy requirements. For example, thermoregulation plays an important role in the behavior of mammals. Those animals that live in colder climates need to keep their bodies warm, while mammals that live in hot and dry climates need to cool down to keep their bodies hydrated. Behavior is an important way for mammals to maintain physiological balance.

There are species of mammals that exhibit almost every type of lifestyle, including vegetative, aquatic, terrestrial, and arboreal. Their ways of moving around their habitat are varied: mammals can swim, run, fly, glide, and so on.

Social behavior also varies considerably. Some species can live in groups of 10, 100, 1000 or more individuals. Other mammals are generally solitary except when mating or rearing offspring.

The nature of activity among mammals also covers the full range of possibilities. Mammals can be nocturnal, diurnal, or crepuscular.

Nutrition

Most mammals have teeth, although some animals, such as baleen whales, have lost them during evolution. Because mammals are widely distributed in a variety of habitats, they have a wide range of feeding habits and preferences.

Marine mammals feed on a variety of prey including small fish, crustaceans, and sometimes other marine mammals.

Among land mammals there are herbivores, omnivores and carnivores. Each individual takes its place in.

Being warm-blooded, mammals require much more food than cold-blooded animals of the same size. Thus, relatively a large number of mammals can have a large impact on populations of their food preferences.

reproduction

Mammals tend to reproduce sexually and have internal fertilization. Almost all mammals are placental (with the exception of oviparous and marsupials), that is, they give birth to live and developed young.

Generally, most mammalian species are either polygynous (one male mating with multiple females) or promiscuous (both males and females have multiple matings in a given breeding season). Since females carry and nurse their offspring, it often happens that male mammals can produce many more offspring during the mating season than females. As a consequence, the most common mating system in mammals is polygyny, with relatively few males fertilizing many females. At the same time, a large number of males do not participate in reproduction at all. This scenario sets the stage for intense competition between males among many species, and also allows females to choose a stronger mating partner.

Many mammalian species are characterized by sexual dimorphism, whereby males are better able to compete for access to females. Only about 3% of mammals are monogamous and only mate with the same female each season. In these cases, males may even participate in the upbringing of offspring.

As a rule, the reproduction of mammals depends on their habitat. For example, when resources are scarce, males spend their energy breeding with a single female and provide food and protection for the young. If, however, resources are plentiful and the female can ensure the well-being of her offspring, the male goes to other females. In some mammals, polyandry is also common, when a female has bonds with several males.

In most mammals, the embryo develops in the uterus of the female until it is fully formed. The born cub is fed with mother's milk. In marsupials, the embryo is born underdeveloped, and its further development takes place in the mother's pouch, as well as feeding with mother's milk. When the calf reaches full development, it leaves the mother's pouch, but can still spend the night in it.

Five species of mammals that belong to the order Monotremes actually lay eggs. Like birds, representatives of this group have a cloaca, which is a single opening that serves for emptying and reproduction. The eggs develop inside the female and receive the necessary nutrients for several weeks before laying. Like other mammals, monotremes have mammary glands and females feed their offspring with milk.

Offspring need to grow, develop and maintain optimal temperature body, but feeding the young with nutrient-rich milk takes a lot of energy from the female. In addition to producing nutritious milk, the female is forced to protect her offspring from all sorts of threats.

In some species, the cubs stay with their mother for a long time and learn the necessary skills. Other species of mammals (such as artiodactyls) are already born quite independent and do not need excessive care.

Role in the ecosystem

The ecological roles or niches filled by more than 5,000 mammal species are varied. Each mammal takes its place in the food chain: there are omnivores, carnivores and their victims - herbivorous mammals. Each species, in turn, affects. Due in part to their high metabolic rates, the impact that mammals have on nature is often disproportionate to their abundance. Thus, many mammals may be carnivores or herbivores in their communities, or play an important role in seed dispersal or pollination. Their role in the ecosystem is so diverse that it is difficult to generalize. Despite their low species diversity, compared to other groups of animals, mammals have a significant impact on the global.

Significance for a person: positive

Mammals are important to mankind. Many mammals have been domesticated to provide humankind with foods such as meat and milk (such as cows and goats) or wool (sheep and alpacas). Some animals are kept as service or pets (eg dogs, cats, ferrets). Mammals are also important to the ecotourism industry. Think of the many people who go to zoos or all over the world to see animals such as whales or whales. Mammals (eg bats) often control pest populations. Some animals, such as rats and mice, are vital to medical and other scientific research, while other mammals can serve as models in human medicine and research.

Significance for a person: negative

plague epidemic

Some species of mammals are believed to have a detrimental effect on human interests. Many species that eat fruits, seeds, and other types of vegetation are crop pests. Carnivores are often considered a threat to livestock or even human life. Mammals common in urban or suburban areas can become a problem if they cause damage to cars when they get on the road or become household pests.

Several species coexist well with humans, including domesticated mammals (eg, rats, house mice, pigs, cats, and dogs). However, as a result of the intentional or unintentional introduction of invasive (non-native) species into ecosystems, they have adversely affected the local biodiversity of many regions of the world, especially the endemic island biota.

Many mammals can transmit diseases to humans or livestock. The bubonic plague is considered the most famous example. This disease is spread by fleas carried by rodents. Rabies is also a significant threat to livestock and can also kill people.

Security

Overexploitation, habitat destruction and fragmentation, the introduction of invasive species and other anthropogenic factors threaten the mammals of our planet. Over the past 500 years, at least 82 species of mammals are considered extinct. About 25% (1,000) of mammal species are currently listed on the IUCN Red List, as they are at various risks of extinction.

Species that are rare or require large ranges are often at risk due to habitat loss and fragmentation. Animals known to threaten people, livestock or crops may die at the hands of humans. Those species that are exploited by humans for quality (for example, for meat or fur), but not domesticated, are often depleted to critically low levels.

Finally, it negatively affects flora and fauna. The geographic ranges of many mammals change due to changes in temperature. As temperatures rise, which is especially noticeable in the polar regions, some animals are unable to adapt to new conditions, and therefore may disappear.

Protective measures include tracking habitats and carrying out a set of measures to protect mammals.

MAMMALS
animals (Mammalia), a class of vertebrates, the most famous group of animals, including more than 4600 species of the world fauna. It includes cats, dogs, cows, elephants, mice, whales, people, etc. In the course of evolution, mammals have carried out the widest adaptive radiation, i.e. adapted to a variety of ecological niches. They inhabit the polar ice, forests of temperate and tropical latitudes, steppes, savannahs, deserts and reservoirs. With a few exceptions (such as anteaters), their jaws are armed with teeth, and mammals can feed on meat, plants, invertebrates, and even blood. They range in size from the tiny pig-bearing bat (Craseonycteris thonglongyai), which is only approx. 29 mm and weighing 1.7 g, to the largest animal known to science - the blue whale (Balaenoptera musculus), reaching a length of approx. 30 m with a mass of 190 tons. Only two fossil brontosaur-like dinosaurs could compete with him. The length of one of them - Seismosaurus - is at least 40 m from the nose to the tip of the tail, but it weighed, according to some experts, approx. 55 tons, i.e. three times smaller than the blue whale. The second dinosaur, Ultrasaurus, is known from a single pelvic bone, but is thought to have been both longer and heavier than the blue whale. However, until this is confirmed by additional fossil remains, the blue whale remains the champion among all animals that have ever inhabited the Earth. All mammals have a series characteristic features their class. Name class Mammalia comes from lat. mamma- female breast, and is associated with the presence in all animals of glands that secrete milk. The term was first used in 1758 by the Swedish botanist Linnaeus in the 10th edition of his book The System of Nature. but scientific definition mammals as a separate group was given even earlier (1693) by the English botanist and zoologist J. Ray in his work Methodological review of the origin of quadrupeds and snakes, and the everyday view of animals as a group of closely related creatures was formed at the dawn of human history.
Origin. The basic plan of the structure of modern mammals was inherited by them from their reptile ancestors, the so-called. synapsids, or animal-like lizards. The age of their oldest known remains is approximately 315 million years, which corresponds to the Pennsylvanian (Upper Carboniferous) period. It is believed that synapsids appeared soon after the appearance of the very first reptiles (anapsids), in the Mississippian (Lower Carboniferous) period, i.e. OK. 340 million years ago, and died out approx. 165 million years ago, in the middle of the Jurassic. The name "synapsids" indicates the presence of a pair of holes in the skull, one on each side behind the orbit. It is believed that they made it possible to increase the mass of the jaw muscles, and, consequently, their power in comparison with animals without such temporal fenestrae (anapsids). Synapsids (class Synapsida) are divided into two orders - pelycosaurs (Pelycosauria) and therapsids (Therapsida). The direct ancestors of mammals was one of the suborders of therapsids - small predatory reptiles cynodonts (Cynodontia). In their various families and genera, in one way or another, the signs of both reptiles and mammals were combined. It is assumed that at least the most evolutionarily advanced representatives of cynodonts possessed such features of animals as the presence of wool, warm-bloodedness, and the production of milk to feed the young. However, paleontologists do not build their theories on assumptions that are not supported by facts, in particular fossilized bones and teeth, which mainly remain from extinct vertebrates. Therefore, in order to distinguish reptiles from mammals, they use several key skeletal features, namely the structure of the jaws, the structure of the jaw joint (i.e., the type of articulation of the lower jaw to the skull), and the osseous system of the middle ear. In mammals, each branch of the lower jaw consists of a single bone - the dentary, and in reptiles it includes several more, including the so-called. articular. In mammals, the jaw joint is formed by the dentary of the lower jaw and the squamous bone of the cranium, while in reptiles it is formed by the articular and quadrate bones, respectively. Mammals have three bones in the middle ear (hammer, anvil, and stirrup), while reptiles have only one (the homologue of the stirrup called the style). Two additional ear bones arose from the quadrate and articular bones, which became the anvil and malleus, respectively. Although it is possible to build a whole sequence of synapsids, increasingly approaching mammals, up to almost complete resemblance to them in appearance and biology, the emergence of animals as a separate group is considered associated with the transformation of the reptilian type of the jaw joint, which moves from an articular-square position to an articulation between dentary and squamosal bones. Apparently, this happened in the middle of the Triassic period, approximately 235 million years ago, however, the earliest fossil remains of true mammals are known only from the end of the Triassic, i.e. im ok. 220 million years.
GENERAL CHARACTERISTICS OF MAMMALS
Some parts of the mammalian skeleton, especially the skull, are simpler than those of their reptile ancestors. For example, as already mentioned, each branch (right and left) of their lower jaw consists of one bone, and in reptiles - of several. In animals, the upper jaw (the intermaxillary bone in front and the maxillary bone in the back) is completely fused with the cranium, while in some reptiles it is connected to it by movable elastic ligaments. In mammals, the upper teeth are found only on the premaxillary and maxillary bones, while in primitive vertebrates they may also be on other bony elements of the roof of the oral cavity, including the vomers (near the nasal passages) and the palatine bones (near the maxillary). Mammals usually have two pairs of functional limbs, but some aquatic forms, such as whales (Cetacea) and sirens (Sirenia), have retained only the front. All animals are warm-blooded and breathe atmospheric air. From all other vertebrates, with the exception of birds and crocodiles, they differ in a four-chambered heart and a complete separation of arterial and venous blood in it. However, unlike birds and crocodiles, mammalian mature red blood cells (erythrocytes) lack nuclei. With the exception of the most primitive members of the class, all mammals are viviparous and feed their young with milk produced by the mammary glands of the mother. Primitive animals, or monotremes, such as the platypus, lay eggs, but the young that hatch from them also feed on milk. In some species they are born, although fully formed, but naked (without hair) and helpless, and their eyes remain closed for some time. In other animals, especially ungulates (goats, horses, deer, etc.), cubs are born completely dressed in wool, with open eyes, and almost immediately able to stand and move. In marsupials, such as kangaroos, cubs are born underdeveloped and endured for some time in a pocket on the mother's stomach.
Wool. The presence of wool covering the body - hallmark animals: only they form hair, i.e. filamentous keratinized outgrowths of the skin (epidermis). The main function of the coat is to insulate the body, facilitating thermoregulation, but it also serves many other purposes, in particular, it protects the skin from damage, can mask the animal due to its color or configuration, or demonstrate its gender. In many mammals, the hair in certain parts of the body has changed significantly and specialized in the course of evolution, turning, for example, into protective quills of a porcupine, rhinoceros horn, vibrissae (sensitive "whiskers") of cats and winter "snowshoes" (leg trim) of a hare. Individual hairs are in most cases cylindrical or oval in cross section, although in some species they are practically flat. Microscopic examination reveals that the hair shaft (above and just below the skin) is a compact, flexible rod composed of hardened dead cells. A typical trunk consists of three concentric layers: a central spongy core formed by loosely lying rectangular cells, often with small layers of air between them, a middle cortical layer that makes up the main part of the hair and is formed by spindle-shaped cells longitudinally located close to each other, and a thin outer skin ( cuticle) of scaly, overlapping cells, the free edges of which are directed towards the free end of the hair. Delicate primary hairs of a human fetus (lanugo), and sometimes a small fluff on the body of an adult, are devoid of a core. Hair cells form under the skin inside the hair follicle (follicle) and are pushed outward by new cells that form underneath. As you move away from the root, i.e. source of nutrition, the cells die and are enriched with keratin - an insoluble protein in the form of long thin fibers. Keratin fibers are chemically bonded to each other, which gives the hair strength. Hair color depends on several factors. One of them is the presence of pigments (coloring substances) called melanins. Despite the fact that the name of these pigments comes from the word "black", their color varies from yellow to red, brown and black. Melanins can appear in individual hair cells as they grow and move away from the follicle. The presence or absence of melanin, its color and quantity, as well as the proportion of air layers between the cells of the stem together determine the whole variety of hair colors. In principle, we can say that its color depends on the absorption and reflection of light by melanin (mainly the cortical layer) and its scattering by the walls of the air layers of the core. For example, black hair contains optically dense, very dark melanin both in the cortex and in the core, so it reflects only a very small part of the light rays. In contrast, the polar bear's fur is completely devoid of pigment, and its color is determined by the uniform scattering of light. The diversity of the hair structure is primarily associated with the shape of the cuticular cells and the location of the core cells. Specific animal species tend to be characterized by a particular coat structure, so a microscope can usually determine its taxonomic nature. A notable exception to this rule is the 150 species of shrews of the genus Crocidura with virtually identical hair. Species determination by microscopic features of hair is currently being replaced by more accurate methods based on the study of DNA and karyotypes (chromosome sets). Hair covering the body is generally divided into two types based on length and texture. Some of them are guard - long, shiny, relatively coarse. They are usually surrounded by one and a half to two times shorter undercoat hair. True seals (family Phocidae), also called earless seals, are covered mainly with coarse outer hair with a sparse undercoat. At fur seals on the contrary, the undercoat is very thick. They belong to the family of eared seals (Otariidae), which also includes sea lions with the same skin as real seals.









Teeth , present in the vast majority of mammals, are solid structures that develop from special connective tissue (mesoderm) cells - odontoblasts and consist mainly of calcium phosphate (apatite), i.e. chemically very similar to bones. However, calcium phosphate crystallizes and combines with other substances in different ways, so that various dental tissues are formed as a result - dentin, enamel and cementum. Basically, a tooth is made up of dentin. (Elephant tusks and, accordingly, ivory are solid dentin; a small amount of enamel that first covers the end of the tusk is quickly erased.) The cavity in the center of the tooth contains the “pulp” that feeds it from soft connective tissue, blood vessels and nerves. Usually, the protruding surface of the tooth is at least partially covered with a thin, but extremely hard layer of enamel (the hardest substance in the body), which is formed by special cells - ameloblasts (adamantoblasts). The teeth of sloths and armadillos are deprived of it; on the teeth of the sea otter (sea otter) and spotted hyena, which have to regularly gnaw hard shells of mollusks or bones, its layer, on the contrary, is very thick. The tooth is fixed in a cell on the jaw with cement, which is intermediate in hardness between enamel and dentin. It may also be present within the tooth itself and on its chewing surface, for example in horses. Mammalian teeth are generally divided into four groups according to their function and location: incisors, canines, premolars (minor molars, pseudomolars, or premolars) and molars (molars). The incisors are located in the front of the mouth (on the premaxillary bones of the upper jaw and, like all teeth of the lower jaw, on the dentary bones). They have cutting edges and simple conical roots. They serve mainly to hold food and bite off parts of it. Fangs (who have them) are usually long rods pointed at the end. There are usually four of them (2 upper and lower), and they are located behind the incisors: the upper ones are in front of the maxillary bones. Fangs are used mainly for inflicting penetrating wounds in attack and defense, holding and carrying food. The premolars are located between the canines and molars. Some primitive mammals have four of them on each side of the upper and lower jaws (16 in total), but most groups have lost some of the false-rooted teeth during evolution, and in humans, for example, there are only 8 of them. The molars located at the back of the jaws, along with premolars are combined into a group of cheek teeth. Its elements may vary in size and shape depending on the nature of the feeding of the species, but usually have a wide, ribbed or tuberculate chewing surface for crushing and grinding food. In fish-eating mammals, such as toothed whales, all teeth are almost the same, approaching a simple cone in shape. They are used only to catch and hold prey, which is either swallowed whole or pre-torn into pieces, but not chewed. Some mammals, notably sloths, toothed whales, and platypuses, develop only one set of teeth throughout their lives (in the platypus, it is present only at the embryonic stage) and are called monophyodonts. However, most of the animals are diphyodont, i.e. they have two changes of teeth - the first, temporary, called milk, and permanent, characteristic of adult animals. Their incisors, canines and premolars are completely replaced once in a lifetime, and molars grow without milk predecessors, i.e. in fact, they are a late developing part of the first change of teeth. Marsupials occupy an intermediate position between monophyodonts and diphyodonts, since they retain all milk teeth, except for the changing fourth premolar. (In many of them, it corresponds to the third cheek tooth, since one premolar has been lost in the course of evolution.) Since teeth are homologous in different mammalian species, i.e. are identical in evolutionary origin (with rare exceptions, for example, river dolphins have more than a hundred teeth), each of them occupies a strictly defined position relative to the others and can be indicated by a serial number. As a result, it is not difficult to write down the set of teeth characteristic of the species in the form of a formula. Since mammals are bilaterally symmetrical animals, such a formula is compiled only for one side of the upper and lower jaws, remembering that to calculate the total number of teeth, it is necessary to multiply the corresponding numbers by two. An expanded formula (I - incisors, C - canines, P - premolars and M - molars, upper and lower jaws - numerator and denominator of a fraction) for a primitive set of six incisors, two canines, eight false-rooted and six molars is as follows:



However, an abbreviated formula is usually used, where only the total number of teeth of each type is indicated. For the above primitive tooth set, it looks like this:


For domestic cow, which does not have upper incisors and canines, the entry takes the following form:


and the person looks like this:


Since all types of teeth are arranged in the same order - I, C, P, M - dental formulas are often further simplified by omitting these letters. Then for a person we get:

Some teeth that perform special functions in the course of evolution can undergo very strong changes. For example, in the carnivore order (Carnivora), i.e. in cats, dogs, etc., the fourth upper premolar (denoted P4) and the first lower molar (M1) are larger than all other cheek teeth and are equipped with sharp blades, cutting edges. These teeth, called predatory teeth, are located opposite each other and act like scissors, cutting the meat into pieces that are more convenient for the animal to swallow. The P4/M1 system is a distinguishing feature of the order Carnivora, although other teeth may also perform its function. For example, the Carnivora milk set does not contain molars, and only premolars (dP3/dP4) are used as predatory ones, and in some representatives of the extinct order Creodonta, two pairs of molars, M1+2/M2+3, served the same purpose.













Skeleton. In mammals, as in all vertebrates, the skeleton consists of a large number of bones that develop independently and are interconnected by ligaments and connective tissue. In some species, it is deeply specialized, but the principle of its structure is the same for all representatives of the class. This fundamental similarity is clearly seen when comparing extreme variants, such as dolphins with a virtually absent neck, whose vertebrae are paper-thin, and giraffes with the same number, but very elongated cervical vertebrae. The skull of mammals is articulated with the vertebral column by two rounded bony protrusions in its back - the occipital condyles. For comparison, the reptilian skull has only one occipital condyle, i.e. only one point of articulation with the spine. The first two vertebrae are called the atlas and the epistrophy. Together with the next five, they make up the seven cervical vertebrae. This number is typical for all mammals, except for sloths (from six to nine) and, possibly, manatees (according to some experts - six cervical vertebrae). Then comes the largest, thoracic spine; ribs are attached to its vertebrae. This is followed by the lumbar (between the chest and pelvis) and sacral vertebrae. The latter are fused together and articulated with the pelvic bones. The number of caudal vertebrae varies greatly depending on the type of animal and reaches several tens. In different mammals, the number of ribs surrounding many vital organs is not the same. They are usually flat and curved. Each rib is movably articulated at one end (proximal) with the dorsal vertebra, and at the other end (distal), the anterior ribs (upper in humans) are attached to the sternum with cartilage. They are called true in contrast to the back (in humans - lower), not connected to the sternum and called false. The distal end of these ribs is either attached to the cartilaginous part of the last true rib, or remains free, in which case they are called oscillating. The sternum consists of a series of more or less flattened bones fused together and is connected by cartilage to the ribs on each side. In bats, it carries a protruding keel for attaching powerful flight muscles. A similar keel on the sternum is found in flying birds and penguins (which "fly" under water), while flightless birds like the ostrich lack it. The shoulder blade is a wide flat bone with a median ridge (awn) on the outer surface. The clavicle is connected at one end to the upper edge of the sternum, and at the other - to the shoulder process (acromion) of the spine of the scapula. The clavicle strengthens the shoulder, so it is primarily characteristic of those mammals (for example, primates) that intensively use their forelimbs for grasping. She is also present in primitive species, in particular, single pass, since it is part of the ancestral (reptilian) shoulder girdle, a skeletal formation that connects the forelimb to the axis of the body. The clavicle has been reduced or lost in the course of the evolution of such groups of mammals that do not need it. For example, it is rudimentary in a horse, since it would only interfere with the lengthening of its stride (only a small strip surrounded by muscles remained), and it is absent in whales. The pelvis (pelvic girdle) serves to attach the hind limbs to the spine.









Limbs. The uppermost bone of the forelimb (human arm) is the humerus. It is attached to the scapula with the help of a spherical joint, and the lower end is connected with two bones of the forearm (underarm) - the radius and the ulna. The wrist usually consists of six to eight small bones (humans have eight) that connect to the bones of the metacarpus, forming the "palm" of the hand. The bones of the fingers are called phalanges. The femur of the hind limb (human leg) is articulated with a spherical joint with the pelvis. The skeleton of the lower leg consists of two bones - the tibia and the tibia. Then comes the foot, i.e. a tarsus of several bones (in humans - seven), connected to the bones of the metatarsus, to which the phalanges of the fingers are attached. The number of toes and hands depends on the type of mammal - from one to five. Five is a primitive (ancestral) state, and, for example, a horse belonging to evolutionarily advanced forms has only one finger on both the front and hind limbs (anatomically, this is a greatly enlarged middle, i.e. third, finger, and the rest are lost during specialization). The deer has functional large third and fourth fingers, forming a cloven hoof; the second and fifth are small, not reaching the ground, and the first ("big") is missing. In most mammals, the ends of the fingers are protected by claws, nails, or hooves, which are keratinized derivatives of the epidermis (the outer layer of the skin). The appearance and function of these structures vary greatly, but their general structure is the same. Mammals that rely on the entire sole when walking, i.e. on the metacarpus and metatarsus, as, for example, bears and people, are called plantigrade, moving relying only on fingers (for example, cats and dogs) - digitigrade, and hoofed forms (cow, horse, deer) - phalangeal. The body cavity of all animals is divided in two by a muscular partition called the diaphragm. In front (in a person - from above) is the chest cavity, which contains the lungs and heart, and behind (in a person - from below) - the abdominal cavity with the rest internal organs except for the kidneys. Only mammals have a diaphragm: it is involved in lung ventilation. The mammalian heart is divided into four chambers - two atria and two ventricles. Each atrium communicates with a ventricle on the same side of the body, but this opening is provided with a valve that allows blood to flow in only one direction. Oxygen-depleted blood, returning to the heart from the organs of the body, enters the right atrium through large veins called hollow. It then pushes into the right ventricle, which pumps it to the lungs via the pulmonary arteries. In the lungs, the blood is saturated with oxygen and releases carbon dioxide. Oxygen-rich blood then enters the pulmonary veins, and from them into the left atrium. Then she pushes from it into the left ventricle, which pumps it through the largest artery - the aorta - to all organs of the body. The lungs are a spongy mass made up of numerous air-filled passageways and chambers surrounded by a network of capillaries. Passing through this network, the blood absorbs oxygen from the air pumped into the lungs and at the same time releases carbon dioxide into it.
Normal blood temperature in different
species of mammals is not the same, and in many bats, rodents and a number of other species it drops noticeably during sleep and seasonal hibernation. Usually close to 38°C, in the latter case it can approach the freezing point. The "warm-bloodedness" characteristic of mammals, i.e. the ability to maintain a constant body temperature is a relative concept. In many species, diurnal fluctuations in this temperature are known; in humans, for example, during the day it rises from the morning low (approx. 36.7 ° C) to about 37.5 ° C in the evening. Desert animals are exposed to intense heat every day, which also affects their body temperature; in camels, for example, it can change during the day by almost 6 ° C. And in a rodent of a naked mole rat living in relatively stable microclimatic conditions of a hole, the latter directly affect body temperature. The stomach of most mammals consists of one section, but in some species there are several, for example, four in ruminants, i.e. artiodactyl animals such as cows, deer and giraffes that chew their cud. Camels and deer are called "false-ruminants" because, although they chew the cud, they differ from the "true" ruminants in having a three-chambered stomach and some signs of teeth, legs and other organs. A number of whales have a long tubular stomach divided into several successive chambers. The lower end of the stomach opens into the small intestine, which, in turn, leads to the large intestine, which leads to the rectum. At the border of the small and large intestines, the caecum branches off from the digestive tract. In humans and some other animals, it ends in a small rudiment - the appendix (appendix). The structure and role of the cecum varies greatly depending on the type of animal. For example, in ruminants and horses, it performs the important function of a fermentation chamber for the digestion of plant fibers and is exceptionally long, while in other mammals it is relatively small, although it takes an active part in digestion. The mammary glands produce milk to feed the young. These structures are laid in representatives of both sexes, but in males they are underdeveloped. In all mammals, except for the platypus and other monotremes, the ducts of the mammary glands open on fleshy outgrowths - nipples, which the young, feeding, capture by mouth. In some species, such as cows, the ducts of the mammary gland first flow into a chamber called a cistern, where milk accumulates, which then flows out through long tubular nipples. Single-pass nipples do not, and the milk ducts open as porous holes in the skin.
NERVOUS SYSTEM
The nervous system functions as an integral whole with the sense organs, such as the eyes, and is controlled in mammals by the brain. The largest part of the latter is called the cerebral hemispheres (in the occipital region of the skull there are two smaller hemispheres of the cerebellum). The brain is connected to the spinal cord. In all mammals, with the exception of monotremes and marsupials, unlike other vertebrates, the right and left cerebral hemispheres are interconnected by a compact bundle of nerve fibers called the corpus callosum. There is no corpus callosum in the brain of monotremes and marsupials, but the corresponding areas of the hemispheres are also connected by nerve bundles; for example, the anterior commissure connects the right and left olfactory regions with each other. The spinal cord - the main nerve trunk of the body - passes through a canal formed by the openings of the vertebrae and stretches from the brain to the lumbar or sacral spine, depending on the type of animal. From each side of the spinal cord, nerves depart symmetrically to different parts of the body. Touch in general terms is provided by certain nerve fibers, the innumerable endings of which are located in the skin. This system is usually supplemented by hairs that act as levers to press on nerve-riddled areas. Vision is more or less developed in all mammals, although some mole rats have small, underdeveloped eyes covered with skin and are hardly even capable of distinguishing light from darkness. The animal sees the light reflected from objects, absorbed by the eye, which transmits the appropriate signals to the brain for recognition. In other words, the eyes themselves do not "see", but only act as transducers of light energy. One of the problems of obtaining a clear visual image is overcoming chromatic aberration, i.e. a fuzzy colored border that appears at the edges of an image formed by a simple lens (a non-composite transparent object with two opposite surfaces, of which at least one is curved). Chromatic aberration is an inherent property of the lens of the eye and occurs because, like a simple lens, it refracts shorter wavelength light (such as violet) more strongly than long wavelength light (such as red). Thus, the rays of all wavelengths are not focused at one point, giving a clear image, but some are closer, others are farther, and the image is blurry. In a mechanical system such as a camera, chromatic aberration is corrected by gluing lenses with different mutually compensating refractive powers. The mammalian eye solves this problem by "cutting off" most of the shortwave light. The yellowish lens acts as a yellow filter: it absorbs almost all ultraviolet (which is partly why a person does not perceive it) and part of the blue-violet part of the spectrum. Not all of the light that enters the pupil and reaches the light-sensitive retina is used for vision. Some of it passes through the retina and is absorbed by the underlying pigment layer. For nocturnal animals, this would mean too much loss of the small amount of available light, so in many such species the bottom of the eye is mirrored: it reflects unused light back to the retina for additional stimulation of its receptors. It is this reflected light that causes the eyes of some mammals to "glow" in the dark. The mirror layer is called the tapetum lucidum (mirror). Mammals have two main types of areolet. The first is fibrous, characteristic of ungulates. Their areolet mainly consists of a shiny layer of connective tissue fibers. The second type is cellular, for example, in carnivores. In this case, it consists of several layers of flattened cells containing fibrous crystals. The mirror is usually located in the choroid behind the retina, but, for example, in some bats and in the Virginia opossum it is embedded in the retina itself. The color that the eyes shine with depends on the amount of blood in the capillaries of the choroid and the content of rhodopsin (purple light-sensitive pigment) in the rod-shaped elements of the retina through which the reflected light passes. Despite the widespread belief that color vision is uncommon in mammals, most of which supposedly see only shades of gray, evidence is accumulating that many species, including domestic cats and dogs, do, at least to some extent, see colors. Color vision is probably most developed in primates, but is also known in the horse, giraffe, opossum, several species of squirrels, and many other animals. Hearing is well developed in many mammals, and for 20% of their species, it largely replaces vision. The hearing aid consists of three main parts. Mammals are the only group of animals with a well-developed outer ear. The auricle picks up sound waves and sends them to the eardrum. On the inner side of it is the next section - the middle ear, an air-filled chamber with three bones (hammer, anvil and stirrup), which mechanically transmit vibrations from the eardrum to the inner ear. It includes the cochlea, a spirally coiled, fluid-filled tube with hair-like outgrowths inside. Sound waves cause fluid vibrations and, indirectly, the movement of hairs, which serves as a stimulation of nerve cells at their base. The frequency range of perceived sounds depends on the type of animal. Many small mammals hear "ultrasound" at frequencies that are too high for human hearing. Ultrasound is especially important for species that use echolocation - the capture of reflected sound waves (echoes) to recognize objects in the environment. This way of orientation is typical for bats and toothed whales. On the other hand, many large mammals can pick up low-frequency "infrasound" that humans also cannot hear. The sense of smell is associated with thin sensory membranes (olfactory mucosa) at the back of the nasal cavity. They capture the molecules of odorous substances present in the inhaled air. The olfactory mucosa consists of nerve and supporting cells covered with a layer of mucus. The endings of its nerve cells carry bundles of olfactory "cilia" up to 20 in number, which together form a kind of fleecy carpet. Cilia serve as odor receptors, and the density of their "carpet" depends on the type of animal. In a person, for example, there are up to 20 million of them on an area of ​​5 cm2, and in a dog - more than 200 million. Odorous molecules dissolve in mucus and enter special sensitive pits on the cilia, stimulating nerve cells that send impulses to the brain for analysis and recognition.
COMMUNICATION
Sound. Mammals use sounds to communicate, such as alarms, threats, or calls to mate (some animals, particularly certain species of deer, only speak during the breeding season). A number of species, including rabbits, have well-developed vocal cords but use them only when under extreme stress. Non-vocal sound communication is known in many mammals: rabbits, for example, knock on the ground with their paws, white-footed hamsters drum with their front paws on hollow objects, and male deer crack their horns on branches. Sound communication plays an important role in the social interactions of animals, since in general they can express all basic emotions with sounds. Bats and toothed whales make sounds for echolocation, allowing them to navigate in the dark or in murky water, where vision would be clearly insufficient for this.
Visual. Mammals communicate with more than just sounds. For example, in some species, the white underside of the tail, if necessary, is shown to relatives as a visual signal. The "stockings" and "masks" of certain antelopes are also widely used to display their condition. A particular example of visual communication is observed in the American pronghorn, which sends messages to other members of its species within a 6.5 km radius using a patch of long white hair on the rump. The frightened animal fluffs up these hairs, which seem to flare up in the sunlight, becoming clearly visible at a great distance.
Chemical. Odors, which are determined by various chemicals in urine, feces, and glandular secretions, are widely used by mammals in social interactions, for example, to mark territory or recognize suitable mating partners. In the latter case, the smell makes it possible not only to distinguish males from females, but also to determine the stage of the reproductive cycle of a particular individual. Chemical signals used for intraspecific communication are called pheromones (from the Greek pherein - to carry and hormon - to excite, i.e. pheromones "transfer excitement" from one individual to another). They are divided into two functional types: signaling and motivating. Signal pheromones (releasers) cause specific behavioral responses of another animal, for example, they attract individuals of the opposite sex, make them follow an odorous trail, flee, or attack an enemy. Motivating pheromones (primers) lead to physiological changes in relatives. For example, the achievement of sexual maturity in house mice is accelerated by the smell of substances contained in the urine of adult males, and slowed down by pheromones in the urine of adult females.
See also ANIMAL COMMUNICATION.
BREEDING
Fish and amphibians usually lay their eggs (eggs) in the water. Their eggs are equipped with membranes that help the developing embryos shed waste and absorb nutrients, primarily from the calorie-rich yolk. The yolk sac and other membranes of this type are located outside the embryo, therefore they are called extraembryonic membranes. Reptiles were the first vertebrates to acquire three additional extraembryonic membranes, allowing them to lay eggs on land and ensure development without an aquatic environment. These shells made it possible for the embryo to receive nutrients, water and oxygen, as well as to excrete metabolic products, being in a non-aqueous environment. The innermost of them - the amnion - forms a bag filled with a brackish liquid. It surrounds the embryo, providing it with a liquid environment similar to that in which the embryos of fish and amphibians are immersed in water, and the animals that possess it are called amniotes. The outermost shell - the chorion - together with the middle one (allantois) performs other important functions. The shell surrounding the fish egg is also called the chorion, but this structure in them is functionally comparable to the so-called. the shiny shell (zona pellucida) of a mammalian egg, which is present even before its fertilization. Animals inherited extraembryonic membranes from reptiles. In oviparous monotremes, these membranes still perform their ancestral functions, since the energy requirements of the embryo are met by the rich reserves of yolk in large shelled eggs. In marsupial and placental embryos, which receive most of the energy necessary for development from the mother, the eggs contain little yolk, and the embryo soon attaches to the wall of the uterus with the help of outgrowths of the chorion penetrating into it. In most marsupials and some placentals, it fuses with the yolk sac to form a primitive placenta called the yolk. The placenta (also called the placenta or placenta) is a formation that provides a two-way exchange of substances between the embryo and the mother's body. Through it, nutrients enter the embryo, its respiration and removal of metabolic products. In most placental mammals, the chorion forms it together with the allantois, and it is called the allantoid. The duration of the period from fertilization of the egg to the birth of the cub varies from 12 days in some marsupials to about 22 months in the African elephant. The number of newborns in a litter usually does not exceed the number of nipples in the mother and, as a rule, is less than 14. However, some mammals have very large litters, for example, a Madagascar tenrec female from the order of insectivores with 12 pairs of mammary glands sometimes gives birth to more than 25 cubs. Usually one embryo develops from a fertilized egg, but polyembryony is also found, i.e. it gives rise to several embryos that separate at the earliest stages of development. Occasionally, this occurs in many species, including completely identical identical twins in humans, but in the nine-banded armadillo, polyembryony is a common occurrence, and the litter, as a rule, consists of "quadruplets". In marsupials, young are born underdeveloped and complete development in the mother's pouch. See also marsupials. Immediately after birth (or, in the case of monotremes, after hatching from eggs), mammals feed on mother's milk. The mammary glands are usually arranged in pairs, which range from one (for example, in primates) to 12, as in tenrecs. At the same time, many marsupials have an odd number of mammary glands and only one nipple is developed in the middle of the abdomen.


KOALA takes care of her "bear" for almost four years.






locomotion
In general, the mechanism of movement (locomotion) is the same in all mammals, but its specific methods developed in many divergent directions. When the animals' ancestors first crawled onto land, their fore and hind limbs were short and widely spaced, making movement on land slow and clumsy. The evolution of mammalian locomotion has been directed mainly towards increasing speed by lengthening and straightening the legs and lifting the torso off the ground. This process required certain changes in the skeleton, including the loss of a number of elements of the reptilian shoulder girdle. Due to the diversity of specialization, the animals have mastered all possible ecological niches. In modern mammals, modes of locomotion include digging, walking, running, jumping, climbing, gliding, flapping flight, and swimming. Burrowing forms such as moles and gophers move below the soil surface. The powerful forelimbs of these mammals are pushed forward so that the paws can work in front of the head, and the shoulder muscles are very strongly developed. At the same time, their hind limbs are weak and unspecialized. The brushes of such animals can be very large, adapted for raking soft soil, or armed with powerful claws for "drilling" hard ground. Many other mammals dig holes in the ground, but digging, strictly speaking, does not apply to their methods of locomotion.



Many small species, such as rats, mice and shrews, are characterized by a relatively massive body with short limbs and usually move in dashes. It is hardly worth talking about some kind of their locomotor specialization. Some mammals, such as bears, are best suited for walking. They belong to the plantigrade type and rely on the feet and palms when walking. If necessary, they can switch to hard running, but they do it clumsily and cannot maintain high speed for a long time. Very large animals are also adapted for walking, such as elephants, in which there is a tendency to elongate and strengthen the upper leg bones while shortening and expanding the lower ones. This turns the limbs into massive columns supporting the enormous mass of the body. Conversely, in fast-running animals such as horses and deer, the lower segments of the legs are rod-shaped, capable of moving quickly back and forth. At the same time, the muscles of the limbs are concentrated in their upper part, leaving mainly powerful tendons below, sliding, as if in blocks, along the smooth surfaces of the cartilage and stretching to the places of attachment to the bones of the feet and hands. Additional adaptations for fast running include the reduction or loss of the outer fingers and the convergence of the remaining ones. The need to catch up with agile prey and to cover long distances in the shortest possible time, searching for it, led to the appearance in cats and dogs of another method of locomotion - on the fingers. At the same time, the metacarpus and metatarsus lengthened, which made it possible to increase the speed of running. Her record for mammals is recorded in cheetahs: approximately 112 km / h. Another main direction in the evolution of rapid movement on the ground was the development of the ability to jump. Most animals, whose life is in direct proportion to the speed of their locomotion, move forward using mainly the pushes of their hind legs. The extreme development of this mode of movement, combined with a change in lifestyle, has led to profound structural transformations of jumping species. Their main morphological change was the elongation of the hind limbs, primarily their lower parts, which led to an increase in the push and the ability to soften the blow upon landing. To provide the strength needed for long successive jumps, the muscles of these limbs have grown strongly in the transverse direction. At the same time, their outer fingers were reduced or disappeared altogether. The limbs themselves spread widely to increase stability, and the animal as a whole became digitigrade. In most cases, the forelimbs have greatly decreased, and the neck has shortened. The tail of such species is very long, like a jerboa, or relatively short and thick, like a kangaroo. It serves as a balancer and to some extent as a steering device. The hopping method of locomotion allows you to achieve maximum acceleration. Calculations show that the longest jump is possible at a take-off angle of 40-44°. Rabbits use a mode of movement intermediate between running and jumping: powerful hind legs push the body forward, but the animal lands on its front paws and is ready to repeat the jump, only once again grouped in its original position. In order to lengthen the jumps and thus cover the distance more efficiently, some animals have acquired a parachute-like membrane that stretches along the body between the fore and hind limbs and is attached to the wrists and ankles. When spreading the limbs, it straightens out and provides sufficient lift for planning from top to bottom between branches located at different heights. The rodent American flying squirrel is a typical example of animals moving in this way. Similar gliding webs have independently evolved in other groups, including the African spinytail and the Australian glider (flying possum). The animal can start flying from almost any position. With its head extended forward, it glides through the air, picking up speed under the force of gravity, sufficient to turn the body upward before landing, so that it comes at her in an upright position. After that, the animal is ready to climb up the tree trunk and, having climbed to the required height, repeat the flight. Among mammals, the kaguans, or woolly wings, living in the Far East and the Philippine Islands, have the most perfect adaptation for planning. Their lateral membrane continues along the neck and tail, reaches the thumbs and connects the other four. The bones of the limbs are long and thin, which ensures maximum stretching of the membrane when the limbs are extended. With the exception of such gliding, which has evolved as a special type of locomotion, no transitions from ground to flapping flight have been observed in modern mammals. The only mammals that can actually fly are bats. The oldest known fossil representatives already had well-developed wings, the structure of which has hardly changed over 60 million years. These flying mammals are thought to have descended from some primitive group of insectivores. The forelimbs of bats are modified into wings. Their most notable feature is the strong elongation of the four fingers, with a flying web between them. However, the thumb protrudes beyond its front edge and is usually armed with a hook-shaped claw. The long bones of the limbs and their major joints have undergone significant changes. The humerus is distinguished by large outgrowths (skewers) to which muscles are attached. In some species, the skewers are long enough to form a secondary articulation with the scapula, which gives the shoulder joint unusual strength, but limits movement in it to one plane. The elbow joint is formed almost exclusively by the humerus and radius, while the ulna is reduced and practically non-functional. The flying membrane usually stretches between the ends of the 2nd-5th fingers and further along the sides of the body, reaching the legs at the feet or ankles. In some species, it continues between the legs from ankle to ankle, surrounding the tail. At the same time, a cartilaginous process (spur) departs from the inside of the ankle joint, which supports the back membrane. The nature of the flight of bats of different genera and species is not the same. Some of them, such as bats, flap their wings measuredly. Folded lips fly very fast, and the flight speed of, for example, bagpipes can change dramatically. Some fly as smoothly as night butterflies. Be that as it may, flight is the main mode of locomotion in bats, and it is known that some migratory species cover up to several hundred kilometers without rest. At least one representative of almost every order of mammals swims well. In fact, all animals, even bats, can, if necessary, stay on the water. Sloths move even faster in it than on land, and some rabbits have mastered this environment as well as muskrats. There are various levels of special adaptation of mammals to life in the water. For example, the mink does not have any special adaptations for this, with the exception of greased fur, and whales in body shape and behavior resemble fish rather than animals. In semi-aquatic forms, the hind feet are usually enlarged and provided with a web between the fingers or a fringe of coarse hair, like an otter. Their tail can be transformed into a paddle or rudder, becoming flattened vertically, like a muskrat, or horizontally, like a beaver. Sea lions have adapted to life in the water even better: their front and hind legs are extended and turned into flippers (the upper segments of the limbs are immersed in the fat layer of the body). At the same time, they still retain thick fur to keep them warm and are able to walk on land on all fours. Real seals went further along the path of specialization. For swimming, they use only their hind limbs, which can no longer turn forward to move on land, and thermal insulation is provided mainly by a layer of subcutaneous fat (blubber). Complete adaptation to life in the water is demonstrated by cetaceans and sirens. It is accompanied by profound morphological changes, including the complete disappearance of the external hind limbs, the acquisition of a streamlined, fish-like body shape, and the disappearance of the hairline. To keep whales warm, like real seals, a thick layer of blubber surrounding the body helps. Translational movement in the water is provided by horizontal fins with a cartilaginous frame located at the back of the tail.
SELF PRESERVATION
All mammals have evolved certain mechanisms of self-preservation, and many have acquired special protective adaptations in the course of evolution.




The African Crested Porcupine is protected by a mane ("comb") of flexible spikes and sharp needles. Spreading them, he turns to the enemy with his tail and makes a sharp movement back, trying to prick the aggressor.








Protective covers. Some animals, such as a hedgehog, are covered with needles and, in case of danger, curl up into a ball, exposing them in all directions. A similar method of protection is used by armadillos, which are able to completely fence themselves off from the outside world with a horny shell, which also protects the body from the sharp spines of cacti, which are the most common vegetation in the habitats of these animals. The North American porcupine went even further in the development of protective covers. It is not only covered with jagged needles, which, stuck in the body of the enemy, can lead to his death, but also very deftly wields a prickly tail, inflicting quick and accurate blows on the enemy.
glands. Mammals also use chemical weapons for protection. This method is most mastered by the skunk, which produces a caustic and very smelly liquid in the paired anal glands at the base of the tail. By contracting the muscles surrounding the glands, it can throw out its thin stream at a distance of up to 3 m, aiming at the most vulnerabilities enemy - eyes, nose and mouth. Keratin is an important component of the outer layer of the skin (epidermis) of mammals. It is a strong, elastic and water-insoluble protein. It is essential for the protection of animals, since it protects the underlying tissues from chemical irritants, moisture and mechanical damage. Areas of the skin that are particularly exposed to the aggressive action of the external environment are protected by a thickened epidermis with an increased content of keratin. An example is calloused growths on the soles. Claws, nails, hooves and horns are all specialized keratin formations. Claws, nails and hooves consist of the same structural elements, but differ in their location and degree of development. The claw consists of two parts - the upper plate, called the claw, and the lower plantar. In reptiles, they usually form two halves of a conical cap enclosing the fleshy end of the finger. In the claws of mammals, the lower plate is reduced and practically does not cover the finger. The upper plate of the nail is wide and flat, and the narrow remnant of the lower one is hidden between its edge and the fingertip. In the hoof, both plates are enlarged, thickened and curved, with the upper one (hoof wall) surrounding the lower one (its sole). The fleshy end of the finger, called the arrow in horses, is thus pushed back and up. Claws are used primarily for digging, climbing and attacking. The beaver combs the fur with a forked claw of the hind paw. Cats usually keep their claws retracted into special cases so as not to dull their ends. Deer often defend themselves with ax-sharp hooves and can kill snakes with them. The horse is famous for its powerful kick of the hind legs, and is able to kick with each leg individually and both at once. Defensively, it can also rear up and sharply strike the enemy from top to bottom with its front hooves.
Horns. In the process of evolution, mammals very early acquired outgrowths of the skull used as weapons. Some species had them already in the Eocene (about 50 million years ago) and have since become more and more characteristic of many ungulates. In the Pleistocene (began about 1.6 million years ago), these outgrowths reached fantastic sizes. In many cases, they are more important for fights with relatives, for example, when males compete for a female, than as a means of protection from predators. In principle, all horns are solid outgrowths on the head. However, they developed and specialized in two different directions. One type can be called true horns. They consist of a usually unbranched bone core extending from the frontal bones, covered with a sheath of hard keratinized horny tissue. This hollow sheath removed from the cranial outgrowths is used to make various "horns" into which they blow, pour wine, etc. True horns are usually present in animals of both sexes and are not shed during their entire lives. The exception is the horns of the American pronghorn. Their horny sheath, like that of real horns, not only bears a small process (sometimes more than one), forming a "fork", but is shed (replaced) every year. The second type is the antlers of deer, which, in their fully developed form, consist only of bone without a horn covering, i.e. actually "horns" they are called incorrectly. These are also processes of the frontal bones of the skull, usually branched. Deer-type antlers are present only in males, although here the caribou is an exception ( reindeer). Unlike real ones, these horns are shed every year and grow back. Rhino horn is also not real: it consists of hardened keratinized fibers (“hair”) glued together. Giraffe horns are not horny structures, but bone processes covered with skin and with normal hair. Real horns are characteristic of the group of bovids - cattle, sheep, goats and antelopes. In wild buffalo-like mammals, they are often strongly thickened at the base and form, as it were, a helmet, for example, in the musk ox and black African buffalo. In most types of cattle, they are only slightly curved. The ends of the horns of all species point upwards to some extent, which increases their effectiveness as a weapon. The horns of the bighorn sheep are the heaviest and largest in relation to the overall size of the animal. In males, they are massive and twisted into a spiral that changes its shape during growth, so that their ends can eventually describe more than one full circle. In combat, these horns are used as a battering ram rather than as a stabbing weapon. In females, they are smaller and almost straight. The horns of wild goats specialized differently. The length gives them an impression. Arcuate, widely diverging in the mountain goat and straight, twisted with a corkscrew in the markhor goat, they are very different from sheep, which, even with a greater overall length, seem smaller, since their ends are closer to the base due to the spiral bend. Horns appear at an early stage in the development of an individual. In very young animals, their rudiments are loosely attached to the frontal bones, can be separated from the skull, and even more or less successfully transplanted onto the head of another animal. The practice of transplanting horns originated in India or the Far East and may have been linked to the origin of the legends of unicorns.
Teeth. In most hornless mammals, the main weapon is the teeth. However, some species, such as anteaters, are deprived of them, and, say, rabbits with perfectly developed teeth, never use them for protection, no matter how great the danger. Most rodents put their chisels to good use when threatened. Bats can bite, but in most cases their teeth are too small to inflict serious wounds. Predators use in battle mainly sharp, long fangs, which are vital to them. Cat fangs are dangerous, but the bite of dogs is more powerful, because in a duel these animals are not able to help themselves with their claws. Some mammals have evolved highly specialized teeth called tusks. They are used primarily for food, but can also serve as weapons. Most wild pigs, such as the European wild boar, dig up edible roots with their long tusks, but they can also inflict a serious wound on the enemy with these teeth. The tusks of the walrus are used to rip up the seabed in search of bivalves. They are well developed in both sexes, although the females are usually thinner. Such a tooth can reach a length of 96 cm with a mass of more than 5 kg. The narwhal is the only cetacean with a tusk. It is usually developed only in males and arises from the left side of the upper jaw. It is a forward-protruding straight, spirally twisted rod that can exceed 2.7 m in length and weigh more than 9 kg. Since it is normally present only in males, one of its uses is probably in fights for females. African elephants are the owners of the largest tusks among living mammals. They use them in combat, for digging and marking territory. A pair of such tusks can reach a total length of 3 m, yielding over 140 kg of ivory.
AGGRESSIVE BEHAVIOR
According to the aggressive behavior of mammals, mammals can be divided into three main groups: harmless (never attacking warm-blooded animals for the purpose of killing), indifferent (capable of provoked attack and killing), and aggressive (killing regularly).
Harmless. Rabbits are perhaps the most harmless of all mammals: they do not even try to pretend that they are fighting, no matter how desperate their situation may be. Rodents are generally harmless, although some species, such as the American red squirrel, can kill and eat a small animal on occasion. The blue whale is the largest and strongest mammal that has ever lived, but it feeds on small crustaceans and fish, thus being among the most harmless creatures.
Indifferent. Large herbivores fall into this category, which are aware of their strength and can attack in case of provocation or danger threatening the young. Male deer are harmless for nine months of the year, but become extremely unpredictable and dangerous during the rutting season. In a group of cattle, the bulls are ready to fight at any time. The fact that the red color infuriates them is a delusion: the bull attacks any object moving in front of its nose, even white. An Indian buffalo may attack a tiger without provocation, perhaps following the instinct to protect its young. An injured or cornered African buffalo is considered one of the most dangerous animals. Elephants, except for individual evil individuals, are harmless outside the mating period. Oddly enough, the passion for killing can develop in donkeys, and it acquires in them the character of a purely sports passion. For example, on the island of Mona off the coast of Puerto Rico lived a donkey who spent his free time hunting wild pigs.
Aggressive. Representatives of the order of carnivores belong to typical aggressive animals. They kill to get food, and normally do not go beyond purely nutritional needs. However, a dog that loves to hunt can kill more game than it can eat at one time. Weasel tends to strangle all the mice in the colony or chickens in the chicken coop and only then take a "break for lunch". The shrew, for all its small size, is extremely pugnacious and is capable of killing a mouse twice its size. Among cetaceans, the killer whale is not without reason called the killer whale. This marine predator can literally attack any animal it encounters. Killer whales are the only whales that regularly feed on other warm-blooded whales. Even huge smooth whales, faced with a flock of these killers, take flight.
SPREAD
The areas of distribution (ranges) of individual species of mammals are extremely diverse and are determined both by climatic conditions and by the isolation from each other of large land masses caused by tectonic processes and continental drift.
North America. Since the isthmus between North America and Eurasia disappeared relatively recently (rising sea levels flooded the land bridge on the site of the Bering Strait that existed 35,000-20,000 years ago), and both regions are located in the Northern Hemisphere, between their faunas, including mammals, there is great similarity. Characteristic animals include moose, reindeer and red deer, mountain sheep, wolves, bears, foxes, wolverines, lynxes, beavers, marmots, hares. Large bulls (bison and bison, respectively) and tapirs live in Eurasia and North America. However, only in North America are species such as pronghorn and bighorn goat, puma, jaguar, black-tailed and white-tailed (Virginian) deer and gray fox.
South America. This continent is very peculiar in terms of the fauna of mammals, although many forms migrated from here through the Isthmus of Panama to North America. One of the features of many local tree animals is the presence of a tenacious tail. Only in South America live rodents of the mumps family (Caviidae), including, in particular, the Patagonian mara, which looks more like a hare than a species close to it - a guinea pig. The capybara is also found here - the largest modern rodent, reaching a mass of 79 kg. Guanaco, vicuña, alpaca and llama, characteristic only of the Andes, are South American representatives of the camelid family (Camelidae). Anteaters, armadillos and sloths come from South America. There are no local species of cattle and horses, but there are many deer and a species of bears - spectacled. Pig-like forms are represented by peculiar bakers. Opossums, some felines (including the jaguar and puma), canines (including the large red wolf), rabbits and broad-nosed monkeys (which differ from the Old World species in a number of significant features) are found here, squirrels are well represented. The mammals of Central America are mostly of South American origin, although some species, such as large climbing hamsters, are unique to this region.
Asia. Large mammals are especially diverse in Asia, including elephants, rhinos, tapirs, horses, deer, antelopes, wild bulls, goats, rams, pigs, felines, canines, bears, and primates, including gibbons and orangutans.
Europe. In terms of fauna, Europe is part of Eurasia, but large mammals are almost extinct here. Deer and fallow deer are still found in protected forests, and wild boars and chamois still live in the Pyrenees, the Alps and the Carpathians. Mouflon - supposedly a close relative of domestic sheep - is known in Sardinia and Corsica. The wild bison virtually disappeared from Europe during World War II. From small mammals in limited quantities, for example, the otter, badger, fox, forest cat, ferret, weasel are still preserved; squirrels and other rodents, hares and rabbits are quite common.
Africa. A very spectacular mammalian fauna still inhabits Africa, where antelopes are especially diverse. Zebras still form large herds; there are many elephants, hippos and rhinos. Most mammal groups are represented in Africa, although such northern forms as deer, rams, goats and bears are either absent or very few in number. The giraffe, okapi, African buffalo, aardvark, gorilla, chimpanzee and warthog are unique to this continent. Most "African" lemurs live on the island of Madagascar.
Australia. australian area long time(perhaps at least 60 million years) was isolated from the rest of the continents and, of course, in terms of the fauna of mammals it is strikingly different from them. Animals characteristic of this region are monotremes (echidna, prochidna and platypus) and marsupials (kangaroos, bandicoots, possums, koalas, wombats, etc.). The wild dingo dog appeared in Australia relatively recently: it was probably brought here by primitive people. Local rodents and bats are found here, but there are no wild ungulates. Distribution across climatic zones. The habitats of wild animals are largely determined by climate. The Arctic and Subarctic are characterized by musk ox, caribou, polar bear, walrus and lemmings. In the northern regions temperate climate inhabited by most deer, bears, rams, goats, bison and horses. Cats and dogs also have a northern origin, but they have spread almost all over the world. Antelopes, tapirs, zebras, elephants, rhinos, feral pigs, peccaries, hippos and primates are typical of the tropics. The southern temperate regions are small in area and are characterized by only a few specialized forms.
CLASSIFICATION
The class of mammals (Mammalia) is divided into two subclasses - the first animals (Prototheria), i.e. monotremes, or oviparous, and real animals (Theria), which include all other modern orders. Marsupials and placental mammals have much in common and are closer in origin to each other than each of these groups is to monotremes. All these animals are viviparous and have a simplified shoulder girdle that is not rigidly attached to the axial skeleton. The subclass is divided into two modern infraclasses - Metatheria (lower animals, i.e. marsupials) and Eutheria (higher animals, i.e. placentals). In the latter, babies are born at relatively late stages of development, the placenta is allantoid type, the teeth and general structure are usually highly specialized, and the brain, as a rule, is rather complex. The orders of living mammals are listed below. SUBCLASS PROTOTHERIA - FIRST BEASTS
Order Monotremata (single pass) includes two families - platypuses (Ornithorhynchidae) and echidnas (Tachyglossidae). These animals reproduce in the same way as their reptilian ancestors, i.e. laying eggs. They combine the characteristics of mammals (wool, mammary glands, three ear bones, diaphragm, warm-bloodedness) with some features of reptiles, for example, the presence of a coracoid (a bone that strengthens the shoulder between the shoulder blade and the sternum) in the shoulder girdle. Modern monotremes are common only in New Guinea and Australia, but the remains of a 63 million year old fossil platypus have been found in Patagonia (South America). Echidnas lead a terrestrial lifestyle and feed on ants and termites, while the platypus is a semi-aquatic animal that eats earthworms and crustaceans.
INFRACLASS METATHERIA - LOWER Beasts
Marsupials have long been attributed to a single order Marsupialia, however, modern studies have shown that within this group there are seven distinct evolutionary lines, which are sometimes distinguished as independent orders. In some classifications, the term "marsupials" refers to the infraclass as a whole, the name of which has been changed from Metatheria to Marsupialia. The order Didelphimorphia (American opossums) includes the most ancient and least specialized marsupials, probably originating in North America in the middle of the Cretaceous, i.e. almost 90 million years ago. Modern forms , such as the Virginian opossum, are promiscuous in their diet and live in a wide variety of conditions. Most of them are omnivorous (some eat mainly fruits or insects) and inhabit tropical latitudes from southern Mexico to northern Argentina (some reach Canada and Chile). A few species carry their young in a pouch, but most do not. The order Paucituberculata (small tuberculate) was the richest in forms in the Tertiary period (about 65-2 million years ago), but now it is represented by only one family Caenolestidae, the species of which are devoid of a real bag. Caenoles are small animals that live on the ground, feed exclusively on insects and live in the temperate forests of the South American Andes. The Microbiotheria order is represented by the only living species, the Chilean opossum from the Microbiotheriidae family, limited in its distribution by the southern beech (notophagus) forests of southern Chile and Argentina. Its relationship with the rest of the marsupials of the New World and Australia, as well as placental mammals, is completely unclear. This is a small animal with a real bag, feeding on insects and building nests on branches in the bamboo undergrowth. The order Dasyuromorphia (predatory marsupials) includes the least specialized Australian marsupials and consists of three families, two of which have only one species. Talitsin, or Tasmanian wolf, from the family of marsupial wolves (Thylacinidae) is a large predator that used to live in Tasmania. Nambat, or marsupial anteater (family Myrmecobiidae), feeds on ants and termites and lives in woodlands in southern Australia. The Dasyuridae family, which includes marsupial mice, marsupial rats, marsupial martens, and marsupial (Tasmanian) devil, unites a wide range of insectivorous and predatory forms inhabiting New Guinea, Australia and Tasmania. All of them are devoid of a bag. The order Peramelemorphia (bandicoots) includes the families of bandicoots (Peramelidae) and rabbit bandicoots (Thylacomyidae). These are the only marsupials that have acquired a chorioallantoic placenta, which, however, does not form the fingerlike villi that characterize the placenta of the same type in higher animals. These small or medium-sized animals with an elongated snout move on four legs and feed mainly on insects and other small animals. They live in Australia and New Zealand. The order Notoryctemorphia (marsupial moles) includes a single representative, the marsupial mole (family Notoryctidae), which resembles real moles in size and body proportions. This insectivorous animal inhabits the sand dunes of the interior of Australia and literally swims in the thickness of the sand, which is facilitated by the large claws of its forelimbs and a hard leathery shield on the nose. The order Diprotodontia unites most of the mammals characteristic of Australia. The families of koalas (Phascolarctidae), wombats (Vombatidae), climbing marsupials (Phalangeridae), marsupial flying squirrels (Petauridae) and kangaroos (Macropodidae) include mainly herbivorous forms, while pygmy possums (Burramyidae) and some marsupial flying squirrels prefer insects, and possums Honey badgers (Tarsipedidae) specialize in pollen and nectar. SUBCLASS THERIA - REAL Beasts.
INFRACLASS EUTHERIA - HIGHER Beasts
As already noted, the higher animals are placental mammals. The order Xenarthra (semi-toothed), formerly called Edentata, is one of the most recent placental evolutionary lineages. It radiated during the Tertiary period (65 - about 2 million years ago) in South America, occupying very peculiar ecological niches. Anteaters (Myrmecophagidae), herbivorous sloths (families Megalonychidae and Bradypodiidae), and mainly insectivorous armadillos (Dasypodidae), which specialize in feeding on ants and termites, belong to the edentulous. In these animals, the spine is strengthened in a special way (vertebrae with additional joints), the skin is reinforced with bone shields or additional layers of connective tissue, and the teeth are without enamel and roots. The distribution of the group is mainly limited to the New World tropics; only armadillos penetrated the temperate zone.



The order Insectivora (insectivora) now occupies the ecological niches of the oldest Mesozoic mammals. In most cases, these are small terrestrial nocturnal animals that feed on insects, other arthropods, and various soil invertebrates. Their eyes, as a rule, are quite small, as are the visual regions of the brain, the hemispheres of which are poorly developed and do not cover the cerebellum. At the same time, the olfactory lobes, responsible for the perception of smells, are longer than the rest of the brain. Systematists are still arguing about the number of families in this order, but six are most often distinguished (for modern species). Shrews (Soricidae) are extremely small mammals; in some of them the metabolic rate reaches the highest level known to animals. Other insectivorous families are moles (Talpidae), golden moles (Chrysochloridae), hedgehogs (Erinaceidae), tenrecs (Tenrecidae) and slittooths (Solenodontidae). Representatives of the detachment live on all continents except Australia and Antarctica. The order Scandentia (tupai) with one family of the same name was not singled out for a long time as a separate group, referring its representatives to primitive primates, to which they are really closely related, as well as to bats and woolly wings. Tupai are similar in size and appearance to squirrels, live only in the forests of East Asia and feed mainly on fruits and insects. The order Dermoptera (woolly wings) includes only two species, also called kaguans. They live in rain forests South-East Asia and are characterized by a broad gliding web that extends from their neck to the fingertips of all four limbs and the end of the tail. The ridge-like, serrated lower incisors are used as scrapers, and the diet of coleopters consists mainly of fruits, buds, and leaves. Order Chiroptera (bats) is the only group of mammals capable of active flight. By diversity, i.e. number of species, it is second only to rodents. The order includes two suborders: fruit bats (Megachiroptera) with one family of fruit bats (Pteropodidae), uniting fruit-eating bats of the Old World, and bats (Microchiroptera), modern representatives of which are usually divided into 17 families. Fruit bats navigate mainly by sight, while bats make extensive use of echolocation. The latter are distributed throughout the world, most of them catch insects, but some are specialized in feeding on fruits, nectar, terrestrial vertebrates, fish, or bloodsucking. The order Primates (primates) includes humans, monkeys and prosimians. Primates have free-rotating arms at the shoulders, well-developed clavicles, usually opposable thumbs (a climbing aid), one pair of mammary glands, and a well-developed brain. The suborder of semi-monkeys includes the armlet, lemurs and lorises, living mainly in Madagascar, galagos from the African continent, tarsiers from the East Indies and the Philippines, etc. The group of broad-nosed monkeys living in the New World includes howler monkeys, capuchins, squirrel monkeys (saimiri), spider monkeys (koats), marmosets, etc. The group of narrow-nosed monkeys of the Old World includes monkeys (macaques, mangabeys, baboons, thin-bodied, proboscis, etc.), anthropoids (gibbons from Southeast Asia, gorillas and chimpanzees from equatorial Africa and orangutans from the islands of Borneo and Sumatra) and you and me. The order Carnivora (carnivores) are carnivorous mammals of various sizes with teeth adapted for feeding on meat. Their fangs are especially long and sharp, their fingers are armed with claws, and the brain is quite well developed. Most are terrestrial, but semi-aquatic, aquatic, semi-arboreal, and underground species are also known. This order includes bears, raccoons, martens, mongooses, civets, foxes, dogs, cats, hyenas, seals, and others. Pinnipeds are sometimes isolated in an independent order Pinnipedia. These are predatory animals, highly specialized for life in the water, but still forced to come to land to breed. Their limbs resemble fins, and their fingers are connected by a swimming membrane. Their normal position on land is recumbent; external ears may be absent, the dental system is simplified (they do not survive food), the hairline is often reduced. Pinnipeds are found in all oceans, but dominate in cold areas. There are three modern families: Otariidae (eared seals, i.e. fur seals, sea lions, etc.), Odobenidae (walruses) and Phocidae (true seals).









Order Cetacea (cetaceans) - these are whales, porpoises, dolphins and animals close to them. They are mammals highly adapted to an aquatic lifestyle. The shape of the body is similar to that of a fish, the tail carries horizontal fins that serve to move in the water, the forelimbs are transformed into flippers, no external traces remain of the hind limbs, and the body is normally hairless. The detachment is divided into two suborders: toothed whales (Odontoceti), i.e. sperm whales, beluga whales, porpoises, dolphins, etc., and baleen whales (Mysticeti), whose teeth are replaced by baleen plates hanging from the sides of the upper jaw. Representatives of the second suborder are very large: they are smooth, gray, blue whales , minke whales, humpback whales, etc. Although it has long been believed that cetaceans are descended from four-legged land mammals, until very recently there was no paleontological evidence for this: all known ancient forms already resembled modern ones and had no hind limbs. However, in 1993 a small fossil whale named Ambulocetus was discovered in Pakistan. He lived in the Eocene, i.e. OK. 52 million years ago, and possessed four functional limbs, representing an important link between modern cetaceans and their four-legged terrestrial ancestors. Most likely Ambulocetus came out on land, like modern pinnipeds. Its legs are quite developed, but, apparently, were rather weak, and this ancient whale moved on them in the same way as sea lions and walruses do. Order Sirenia (sirens) are highly specialized aquatic mammals that are not able to live on land. They are large, with heavy bones, a tail-fin flattened in a horizontal plane, and forelimbs transformed into flippers. No traces of the hind limbs are visible. Modern representatives of the detachment are found in warm coastal waters and rivers. The genus Hydrodamalis (sea, or Steller's, cows) is extinct, but relatively recently met in the northern part of the Pacific Ocean. Today living forms are represented by manatees (Trichechidae), living in the coastal waters of the Atlantic Ocean, and dugongs (Dugongidae), found mainly in quiet bays of the Red Sea, Indian and South Pacific Oceans. The order Proboscidea (proboscis) now includes only elephants, but it also includes extinct mammoths and mastodons. Modern representatives of the order are characterized by a nose extended into a long, muscular grasping trunk; greatly enlarged second upper incisors forming tusks; powerful columnar limbs with five fingers, which (especially the outer ones) are more or less rudimentary and surrounded by a common cover; very large molars, of which only one is used at a time on each side of the upper and lower jaws. Two types of elephants are common in the tropics of Asia and Africa. The order Perissodactyla (equids) unites ungulates, leaning on a greatly enlarged middle (third) toe. False-rooted and molars in them gradually pass into each other, although the latter are distinguished by massive crowns square in plan. The stomach is simple, the caecum is very large, the gallbladder is absent. This order includes tapirs, rhinos, horses, zebras and donkeys. The order Hyracoidea (hyraxes) includes the only family distributed in Western Asia and Africa. Hyraxes, or zhiryaks, are relatively small animals in which the upper incisors grow constantly and are slightly longitudinally curved, like in rodents. Molar and false-root teeth gradually pass into each other; on the front feet, the three middle fingers are more or less the same, the fifth is smaller, and the first is rudimentary; hind legs with three well-developed toes, the first is absent, the fifth is rudimentary. There are three genera: Procavia (rocky or desert hyraxes), Heterohyrax (mountain or gray hyraxes) and Dendrohyrax (tree hyraxes).



The order Tubulidentata (aardvarks) is now represented by a single species, the aardvark, living in sub-Saharan Africa. This medium-sized mammal is covered with sparse coarse hair; its numerous teeth are highly specialized, its ears are large, the first toe on the front paws is absent, but the hind legs have five approximately equal fingers, the elongated muzzle is elongated into a tube, the lifestyle is terrestrial and burrowing. The aardvark feeds mainly on termites.



The order Artiodactyla (artiodactyls) unites animals resting on the phalanges of the third and fourth fingers. They are large, approximately equal to each other, and their ends are surrounded by a hoof. Pseudo-molar and molars are usually well distinguished; the latter - with wide crowns and sharp tubercles for grinding plant foods. The clavicle is missing. Terrestrial lifestyle. Many species belong to the group of ruminants. The living representatives of the order are pigs, hippos, camels, llamas and guanacos, deer, deer, buffaloes, sheep, goats, antelopes, etc.



The order Pholidota (lizards, or pangolins) includes animals that are probably closely related to the edentulous: they are devoid of teeth, and their body is covered with scales. The single genus Manis comprises seven well-separated species. The order Rodentia (rodents) is the richest in species and individuals, as well as the most common group of mammals. Most species are small; large forms include, for example, beaver and capybara (capybara). Rodents are easily recognizable by the nature of their teeth, which are adapted for cutting and grinding plant foods. The incisors of each jaw (two each above and below) are strongly protruding, chisel-shaped and constantly growing. Between them and the molars is a wide toothless gap - diastema; fangs are always absent. Different kinds rodents are terrestrial, semi-aquatic, burrowing or arboreal. This squad includes squirrels, gophers, mice, rats, beavers, porcupines, guinea pigs, chinchillas, hamsters, lemmings and many other animals. The order Lagomorpha (lagomorphs) includes pikas, hares and rabbits. Its representatives are most numerous in the Northern Hemisphere, although they are distributed more or less everywhere. They were absent in the Australian region, where they were brought by white colonists. Like rodents, they have two pairs of large, protruding, chisel-shaped incisors, but there is an additional pair on top, located directly behind the front. Most species are terrestrial, but some American forms are semi-aquatic. The order Macroscelidea (jumpers) includes animals that have long been classified as insectivorous (order Insectivora), but are now considered a completely separate line of evolution. Jumpers are distinguished by well-developed eyes and ears, as well as an elongated muzzle, forming a flexible, but not able to fold proboscis. These features help them find food - various insects. Jumpers live in African semi-deserts and bushes.
Scientific and technical encyclopedic dictionary - (animals), class of vertebrates. Includes oviparous, or cloacal, mammals (first animals) and viviparous mammals (true animals). The first mammals descended from animal-like reptiles, apparently at the beginning of the Triassic or ... Modern Encyclopedia

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Class characteristic.mammals- warm-blooded (homeothermic) amniotes; the body is covered with hair; viviparous; babies are fed with milk. Have a large brain; its anterior section (hemisphere) has a "new cortex" - neopallium - from the gray medulla; it provides a high level of nervous activity and complex adaptive behavior.

The organs of smell, sight, and hearing are well developed. There is an external ear; There are three bones in the middle ear: the hammer, anvil, and stirrup. Bats, dolphins, and some other mammals use ultrasonic echolocation to navigate. Skin with numerous sebaceous and sweat glands, some of which have been converted into lactiferous and odorous glands. The skull is synapsid, articulated with the spine by two condyles; heterodont teeth sit in the alveoli; the lower jaw is only dentary. They breathe with lungs having an alveolar structure. The body cavity is divided by the diaphragm into thoracic and abdominal sections. The intestinal tube becomes more complicated, sometimes a multi-chambered stomach is formed, the caecum increases. Herbivorous animals develop symbiotic digestion.


African elephant(Loxodonta africana)

The heart is four-chambered, two circles of blood circulation, only the left aortic arch is preserved; erythrocytes are non-nuclear. The kidneys are metanephric. Widespread throughout; inhabit all environments, including soil (soil), water bodies and surface layers of the atmosphere. Very influential members of almost all biocenoses. They are important for humans: farm animals, commercial species, keepers of human and domestic animal diseases, pests of agriculture and forestry, etc.

Origin and evolution of mammals. Mammals descended from theromorphic (animal-like) reptiles that appeared back in the Upper Carboniferous, which had a number of primitive features: amphicoelous vertebrae, movable cervical and lumbar ribs, and small brain sizes. At the same time, their teeth sat in the alveoli and began to differentiate into incisors, canines, and molars. Many animal-like reptiles had a secondary bony palate, and the occipital condyle was two or three-parted; they formed a double articulation of the lower jaw with the skull: through the articular and square and through the dentary and squamous bones. In this regard, the dentary in the lower jaw increased, while the square and articular, on the contrary, decreased; while the latter did not grow to the lower jaw. Theromorphic reptiles differed little from their ancestors - the cotylosaurs that lived in humid biotopes - and retained many features of the organization of amphibians. This may explain the presence of skin with numerous glands and other features in mammals.

For a long time during the Permian and most of the Triassic periods, theromorphic reptiles, having formed a number of groups of herbivorous, predatory and omnivorous species, flourished in land biocenoses and died out only in the Jurassic period, unable to withstand competition with progressive archosaurs that had appeared by that time (see above the origin of reptiles ). Relatively small theromorphs, apparently, were pushed back by competitors and enemies to less favorable biotopes (swamps, thickets, etc.). Life in such conditions required the development of sensory organs and the complication of behavior, the strengthening of communication between individuals. In these groups of medium-sized and less specialized animal-toothed (theriodont) reptiles, a new line of development began. the upper olfactory shell, which provided heating and humidification of the inhaled air; the appearance of three-cusp teeth; an increase in the cerebral hemispheres of the forebrain, the formation of soft lips, which opened up the possibility of sucking milk by the cubs; the appearance of an additional articulation of the lower jaw with the skull, accompanied by a reduction of the quadrate and articular bones, etc. However, the assumptions of G. Simpson (1945, 1969) about the polyphyletic (from different groups of theromorphic reptiles) origin of individual subclasses of mammals were not justified.



Cheetah(Acinonyx jubatus)

It can be considered proven that both subclasses of mammals arose in the Triassic period from one initial group of animal-like reptiles with primitive three-tuberculate teeth - carnivorous cynodonts (Tatarinov, 1975). By this time, they had acquired a secondary palate, which strengthened the jaw apparatus, differentiated dental system and a physique that resembled mammals (in particular, the setting of paired limbs under the body). Apparently, they had a diaphragm separating the body cavity, and other signs of mammals. The oldest known mammal - erythrotherium - was small, smaller than a rat. The ways and time of the further formation and evolution of the two subclasses of mammals remain unclear.

Upper Triassic mammals are already divided into two branches (subclasses), in each of which a double articulation of the jaws arose and the formation of the dental system and the formation of "occlusion" - a close closure of the teeth of the upper jaw with the lower, increasing the possibility of mechanical processing of food. The first branch - a subclass of the first beasts - Prototheria known from the sediments of the Triassic period by the remains of small animals with three-pointed molars - Triconodontia. From them originated multituberous - Multituberculata(died out at the end of the Cretaceous) and monotremes - Monotremata, currently represented by the platypus and echidnas. The second branch - real animals - Theria- gave rise to the vast majority of modern mammals (infraclasses - marsupials - Metatheria and placental - Eutheria).

It took a long time for the formation of a new class - mammals. Brain development also progressed slowly.

In theromorphic reptiles, the most developed part of the brain was the cerebellum. On this basis, cynodonts (as well as all animal-like reptiles) should be called "metencephalic animals". On the way to mammals, there was a gradual increase in the forebrain. In this, mammals differ sharply from theromorphic reptiles, earning the name telencephalic group.

For two thirds of its geological history mammals remained small creatures that looked like rats and did not play a significant role in nature. Their rapid progress in the Cenozoic, obviously, was associated not only with the successive accumulation of many adaptations that led to the formation of warm-bloodedness and an increase in the energy level (energy of vital activity, according to A. N. Severtsov), live birth and feeding of young with milk, but especially with the development of organs the senses, the central nervous system (cerebral cortex), and the hormonal system. Taken together, this led not only to the improvement of the organism as an integral system, but also ensured the complication of behavior. The consequence was the development of connections between individuals and the formation of complex dynamic groupings. Such "socialization" of relationships in mammalian populations (as in birds) has created new opportunities in the struggle for existence and position in biocenoses.

The Alpine cycle of mountain building at the end of the Mesozoic and at the beginning of the Cenozoic era changed the face of the Earth; high ridges rose, the climate became more continental, its seasonal contrasts increased, and it became colder on a significant part of the Earth's surface. Under these conditions, the modern flora was formed with the dominance of angiosperms, especially dicotyledonous plants, while the flora of cycads and gymnosperms became poorer. All this put large and infertile herbivorous and predatory reptiles in a difficult position, while smaller warm-blooded birds and mammals more easily adapted to change. Switching to feeding on small animals and high-calorie fruits, seeds and vegetative parts of angiosperms, they multiplied intensively, successfully competing with reptiles. The result was the extinction of the reptiles discussed above; it ended the Mesozoic era, and the wide adaptive radiation of mammals and birds opened the Cenozoic era.



bottlenose dolphin or bottlenose dolphin(Tursiops truncatus)

In the Jurassic period, 6 orders of mammals were formed, and in the Paleocene (60 million years ago) there were already at least 16 orders, 9 of which - Monotremata, Marsupialia, Insectivora, Dermoptera, Primates, Edentata, Lagomorpha, Rodentia, Carnivora- have survived to the present day. The first marsupials were found in the Upper Cretaceous deposits of North America and the Lower Tertiary layers of America and Eurasia; some species live in America and in our time. The preservation of a variety of marsupials in Australia is explained by the fact that it separated from other continents even before the placental settlement. Emerging, apparently, not later than marsupials, placental mammals at first developed slowly. But their main advantage - the birth of more formed cubs, which reduced infant mortality, made it possible to displace marsupials almost everywhere. In our time, they form the core of the mammalian fauna and are represented by a wide variety of life forms that have occupied almost all landscapes of the Earth.

A variety of adaptations of mammals contributed to the development of not only land, but also fresh and marine waters, soil, and air. They ensured an unusually wide use of food resources compared to other vertebrates - the range of nutrition of mammals is more diverse than the composition of the food of other terrestrial and aquatic vertebrates, which increases the importance of mammals in the biosphere and their role in the life of various biocenoses.

Mammal class system and review of modern groups. The class Mammals is divided into two subclasses and includes 19 modern and 12-14 extinct orders. There are 257 families (139 extinct) and about 3000 genera (about 3/4 extinct); about 6,000 species have been described, of which 3,700-4,000 are living. In the modern fauna, there are approximately 2 times less species of mammals than birds (8600). At the same time, a more significant role of mammals (besides humans) in the life of the biosphere is obvious. This can be explained by the fact that the ecological niches of mammalian species are, on average, wider than those of birds.

Accordingly, their biomass (the total mass of all individuals in a given biocenosis) is usually higher than that for birds.

Relationships between orders of placental mammals have not been sufficiently clarified. Undoubtedly, the order of insectivores (remains from the Cretaceous period) is close to the ancestral forms; it has survived to the present day and, in addition, gave rise to woolly wings,

Mammals are the most highly organized and youngest class of animals, which are characterized by the following features:

  • hairline
  • skin glands
  • warm-bloodedness
  • constant body temperature
  • developed cerebral cortex
  • live birth
  • care of offspring
  • complex behavior.

All this allowed mammals to win a dominant position in the animal kingdom. They live in all environments: on land, in soil, in water, in the air, on trees, in all natural areas.

The ecological types of mammals (life forms) are determined by their habitat: aquatic and semi-aquatic have a streamlined fish-like body shape, flippers or membranes on their paws; ungulates living in open areas have high slender legs, a dense body, and a long movable neck. Therefore, among representatives of different subclasses, orders, families, there may be similar life forms due to the same living conditions. This phenomenon of nature is called convergence, and signs of similarity are called homologous.

A highly developed nervous system allows mammals to better adapt to environmental conditions and more fully use Natural resources when obtaining food, when protecting from enemies, when arranging holes, shelters.

The transfer of experience, the training of young animals, and the foresight of the course of many events made it possible for animals to better preserve their offspring and occupy new territories.

Their population structure is different: some consist of living alone or in families in a permanent place, others roam in a herd or flock. A rather complex system of subordination plays an important role when there is a selection for the best organization of a herd or pack.

In food chains, mammals also occupy different positions: some are primary consumers of plant foods (consumers of the 1st order), others are carnivorous, peaceful (insect- and plankton-eating - consumers of the 2nd order), others are predatory (attacking large active prey - consumers of the 2nd and III order). Mixed nutrition is characteristic of primates, predators and rodents. The relationship of animals with plants is very close, which, on the one hand, are an object of eating (in this case, fruits and seeds often spread), and on the other hand, they protect themselves from them with the help of thorns, thorns, unpleasant odor, bitter taste.

Of the entire animal kingdom, man is more closely related to mammals: 15 species are domestic animals, in addition, 20 species are bred in cages. fur animals, as well as laboratory animals (mice, rats, guinea pigs, etc.). Domestication continues at the present time: new breeds are bred and old ones are improved by hybridization with wild animals.

An important role in the human economy is played by hunting and sea fishing, acclimatization of animals from other continents.

At the same time, there are harmful animals that attack humans and domestic animals, carriers of diseases, pests of crops, gardens, and food supplies. To reduce the negative impact of these animals on nature and human economy, they study the structure of their populations, population dynamics, food resources - all these data are entered into a computer, as a result of which they receive a forecast for the future, develop recommendations that determine ways and means of influencing the population in order to limit her harmfulness.

The number of mammal species under the influence of human activity is constantly declining as a result of hunting, the destruction of predators, the destruction of habitats for wild animals, the protection of agricultural plants from rodents (treatment of fields with pesticides), forest and steppe fires, etc.

The Red Book of the USSR (1984) lists 54 species and 40 subspecies of animals. For their protection, reserves, wildlife sanctuaries, national parks are organized, their breeding is organized, hunting and fishing are prohibited. Thanks to these measures, bison, kulan, Bukhara deer, tiger, eastern leopard, goral were saved from extinction; the number of saiga, sable, and beaver has been restored.

In the modern fauna there are 4000-4500 species of mammals, including within Russia - 359 species, in Ukraine - 101. Mammals are common on all continents, with the exception of Antarctica, in terrestrial, marine and freshwater biocenoses. Some species actively fly in the air, others live in the soil. Most species live in various terrestrial biocenoses. In connection with adaptation to life in different conditions, the external appearance of these animals is very different, but they differ sharply from all other features of the internal and external structure.

Class characteristic

Mammals, or animals, are top class vertebrates, whose organs, especially the forebrain cortex, have reached the highest differentiation at the present stage of development.

Thanks to the progressive development of the central nervous system, warm-bloodedness, the presence of hair, bearing cubs in the mother's body and feeding them with milk, mammals won the competition with reptiles and other vertebrates and firmly conquered not only land, but also other habitats.

body integuments. Like all vertebrates, mammalian skin consists of a multi-layered epidermis and corium. Outside, the body is covered with the epidermis, the upper stratum corneum in the form of separate dead cells constantly disappears. The renewal of the epidermis occurs due to cell division of the Malpighian layer. The corium is built from fibrous connective tissue, the deep layers of which (the so-called subcutaneous tissue) contain fat cells. In addition, mammalian skin is rich in sweat glands, and many species have scent glands.

All mammals are characterized by the presence of mammary glands, which are modified sweat glands. The ducts of the mammary glands open in certain areas of the skin of the abdominal side. With the exception of monotremes, all mammalian mammary glands are equipped with nipples. Their number varies from 1 to 14 pairs. The mammary glands secrete milk, which is fed to newborns (hence the name of the class).

Of the horny formations of the skin (hair, nails, claws, hooves), hair is the most typical of mammals. In most animals, the hairline is developed on the entire surface of the body (absent on the lips, in some - on the soles). Mammalian hair is heterogeneous. Large, long, hard, protruding hairs are called vibrissae, they are located at the end of the muzzle, belly, limbs, serve as organs of touch, their bases are connected with nerve endings.

The hair consists of a trunk and a root. The trunk is built of a heart-shaped substance, covered with a cortical layer and outside with a skin. There is air in the cavity of the hair. The hair root ends with a bulb, at the base of which the hair papilla enters. It is rich in blood vessels and serves to nourish the hair. The hair papilla is located in the hair bag, into which the ducts of the sebaceous glands open, secreting a fatty substance that lubricates the hair. The skin of mammals is rich in sebaceous and sweat glands. The latter secrete sweat, due to which thermoregulation is carried out. In temperate and northern latitudes, most species change their hairline twice a year, molting occurs in autumn and spring.

Mammals, like birds, are warm-blooded animals. Their body temperature is constant (in different species it ranges from 37 to 40 ° C), only in oviparous body temperature largely depends on the ambient temperature and ranges from 25-36 ° C. Perfect thermoregulation of most mammals is ensured by the presence of sweat glands, hairline, fatty subcutaneous tissue, and breathing also takes part in thermoregulation.

Skeleton. The skeleton consists of a skull, spine, limb girdles, and bones of paired limbs. The skull of mammals is characterized by a large volume of the cranial, or brain, box. Its bones grow together at the seams quite late, therefore, during the growth of the animal, the brain can increase in volume. The lower jaw consists of only one (dentary) bone and is attached to the paired temporal bone. The other two bones of the jaw became the auditory ossicles, the hammer and anvil. Thus, mammals have three auditory ossicles - the stirrup, hammer and anvil, while amphibians, reptiles and birds have only one - the stirrup (see Table 18).

In the skeleton of mammals, there is a clear division of the spine into five sections: cervical, thoracic, lumbar, sacral and caudal. A constant number of cervical vertebrae (7) is characteristic. On the front side of one of the two cervical vertebrae - the atlas - there are two articular surfaces, like in amphibians. The ribs are attached to the vertebrae of the thoracic region, with their cartilaginous part they are connected to the sternum, or sternum, forming the chest. The sacral vertebrae fuse together and are connected to the bones of the pelvic girdle. The number of tail vertebrae ranges from 3 (in the gibbon) to 49 (in the long-tailed pangolin). The degree of mobility of individual vertebrae is different. The most mobile vertebrae are in small running and climbing animals, so their body can bend in different directions, curl up into a ball, etc. The mobility of the vertebrae is due to the articulation of their flat surfaces with cartilaginous discs (menisci) located between the vertebrae.

The forelimb belt consists of paired shoulder blades and clavicles (the latter are not developed in many species). The composition of the forelimb includes the shoulder, two bones of the forearm (ulna and radius) and a hand with phalanges of the fingers.

The hind limb girdle consists of three paired large bones, which in most mammals fuse with the sacral vertebrae. The composition of the hind limb includes the femur, two bones of the lower leg (large and small) and the foot with the phalanges of the fingers. As a result of adaptation to a different type of movement, the skeleton of the limbs in different mammals has changed greatly. In bats, very long phalanges of fingers support a stretched membrane-wing plane, one-toed horse legs are adapted for fast running, cetacean flippers for swimming, hind legs of kangaroos and jerboas for jumping, etc.

Muscular system. In mammals, it is exceptionally developed, complex and has several hundred individual specialized muscles. Chewing and mimic muscles, especially in monkeys and humans, as well as subcutaneous muscles, reach high development. A typical muscular formation of mammals is the abdominal obstruction, or diaphragm (the muscular septum separating the chest cavity from the abdominal cavity). The diaphragm plays a big role in breathing. When lowering and raising the diaphragm, the volume of the chest changes and intensive ventilation of the lungs is carried out.

Digestive system. The digestive organs begin with a preoral cavity located between the fleshy lips (they are developed only in mammals) and the jaws. On the upper and lower jaws there are teeth differentiated into certain groups depending on the type of nutrition. There are incisors, canines and molars. These groups of teeth perform various functions: biting off and grinding food, capturing and killing prey, etc. The structure of the teeth is associated with the lifestyle of the animal. The tooth consists of 1-2 roots and a crown. Teeth are built from dentine, cementum and enamel, located in the sockets of the jaw bones. The echidna, anteater, and some cetaceans have no teeth. During the development of the animal, two changes of teeth occur - milk and permanent.

At the bottom of the mouth is the tongue, it is involved in chewing and swallowing food. The surface of the tongue is covered with numerous taste buds. The ducts of three pairs of large salivary glands open into the oral cavity. Saliva not only moisturizes food - it contains enzymes that break down starch into glucose during chewing. Thus, food processing begins already in the oral cavity.

Further, food enters the pharynx, esophagus, and from it into the stomach. The structure of the stomach, consisting of cardiac and pyloric sections, is diverse, which is associated with the nature of food. There are many glands in the walls of the stomach. The gastric juice secreted by the glands contains hydrochloric acid and enzymes (pepsin, lipase, etc.). In the stomach, the process of digestion continues. The stomach of ruminant ungulates, which eat a large amount of hard-to-digest coarse plant food, has a particularly complex structure. Digestion of food continues in the duodenum, where the ducts of the liver and pancreas flow. In the small intestines, the breakdown of proteins, fats and carbohydrates is completed and the absorption of essential nutrients occurs. On the border between the small and large intestines in some mammals is the caecum and appendix. Undigested food remains enter the large intestine and are expelled through the rectum.

Respiratory system. The respiratory organs in all mammals begin with the nasal cavity, which has respiratory and olfactory sections. When breathing, air from the nasal cavity enters the larynx, which is supported by several laryngeal cartilages formed by the second and third gill arches. The vocal cords are stretched between the thyroid and arytenoid cartilages. From the larynx, air enters the trachea, which divides into two bronchi. Each of the bronchi enters one of the lungs, branches there, forming a dense network. The smallest pulmonary passages - bronchioles - open into dilated pulmonary vesicles, or alveoli. In the walls of the alveoli, the thinnest blood vessels branch - capillaries, in which gas exchange occurs. The lungs have a complex cellular structure, their respiratory surface is 50-100 times the surface of the body. Contractions of the diaphragm and intercostal muscles increase the volume of the chest cavity, air is pumped into the lungs, and inhalation occurs. When the muscles relax, the volume of the chest cavity decreases, exhalation occurs.

excretory system. The excretory organs are characterized by the fact that the bladder does not open into the cloaca, but into the urethra. Paired ureters open into the bladder, originating from paired bean-shaped secondary kidneys located in the lumbar region under the spine.

Circulatory system mammals is close to the circulatory system of birds: the heart is four-chambered, the large and small circles of blood circulation are completely separated, but there is not a right, but a left aortic arch (in birds, a right aortic arch). Red blood cells in the formed state are devoid of nuclei.

Nervous system and sense organs. The nervous system has the same sections as in other vertebrates (anterior, interstitial, midbrain, cerebellum and medulla oblongata), but its level of development is much higher. The forebrain, which covers the midbrain and cerebellum, reaches the greatest size and complexity. The surface of the cerebral cortex increases due to convolutions and furrows, the number of which is especially large in higher mammals. In the cerebral cortex there are centers of higher nervous activity that coordinate the work of other parts of the brain and determine the complex behavior of mammals. The cerebellum also progresses strongly, with which the maintenance of muscle tone, balance and proportionality of movements is associated.

The level of development of the sense organs depends on the way of life of animals and obtaining food. For the inhabitants of open spaces, vision is of paramount importance, for nocturnal and twilight animals, inhabitants of forests and thickets of shrubs, reservoirs and burrows, smell and hearing.

The sense of smell in mammals is more developed than in other groups of terrestrial vertebrates. In the upper posterior part of the nasal cavity, a complex system of olfactory turbinates is developed, their surface is covered with a mucous membrane of the olfactory epithelium. The complexity of the structure of the olfactory shells corresponds to the sharpness of the sense of smell. Taste organs are taste buds in the mucous membrane of the mouth and tongue.

The organs of hearing are well developed in the vast majority of mammals. The organ of hearing consists of three sections: the outer, middle and inner ear. The outer ear (pinna) and the external auditory meatus are a kind of filter antenna that amplifies sounds important to the animal and attenuates constant noise. At aquatic mammals and inhabitants of the soil, the auricle is reduced. The middle ear contains three auditory ossicles, which ensure the perfect transmission of sound waves to the inner ear. The inner ear consists of the auditory and vestibular sections.

In the auditory region, a spirally twisted cochlea is very developed with several thousand of the finest fibers that resonate when sound is perceived. The vestibular region includes three semicircular canals and an oval sac, it serves as an organ of balance and perception of the spatial position of the body. The hearing range of mammals is much wider than that of birds and reptiles, the cochlea allows mammals to distinguish the highest frequencies.

The eye of mammals is covered with a fibrous tissue - the sclera, which in front passes into a transparent cornea. Under the sclera there is a choroid with blood vessels supplying the eye, in front it thickens and forms the iris. The iris is located directly in front of the lens, plays the role of a diaphragm, regulates the illumination of the retina by changing the size of the pupil. The lens has a lenticular shape, it is enlarged in nocturnal and crepuscular animals. Accommodation is achieved only as a result of a change in the shape of the lens. The retina is adjacent to the inner side of the choroid - a light-sensitive layer consisting of receptors (rods and cones) and several types of neurons. Many mammals have the ability to distinguish colors; color vision is well developed in humans and higher primates. Horses, for example, distinguish four colors. Vision is well developed in nocturnal animals, in particular, cats distinguish six primary colors and 25 shades of gray. In animals that lead an underground lifestyle, vision is reduced (some moles, mole rats, etc.).

reproduction. The reproductive organs in the male are represented by paired testes, in the female - by paired ovaries. Fertilization is internal. The fertilized egg begins to divide and descends through the oviduct into the uterus, where the intrauterine development of the embryo occurs. In most mammals, during the development of the embryo, the placenta is formed in the uterus, gas exchange occurs through it, the embryo is nourished and the metabolic products are excreted. At oviparous mammals the placenta is absent, in marsupials it is rudimentary. The vast majority of mammals are characterized by live birth, and only oviparous ones lay large, yolk-rich eggs. All mammals feed their young with milk. They are distinguished by a high degree of care for offspring. Most mammals build special nests, even after milk feeding is completed, they take care of their young for a long time and diligently, train them.

Systematics. According to the characteristics of reproduction and organization, modern mammals are divided into three subclasses: cloacal (Monotremata), marsupials (Marsupialia) and placental (Placentalia) (Table 20).

Table 20. The division of mammals according to the characteristics of reproduction and organization
Subclass Number of species) Spreading Characteristic features Lifestyle
Oviparous or cloacal 4 (platypus and 3 species of echidnas) Australia, New Guinea and Tasmania Primitive: in the shoulder girdle there are coracoids; there is a cloaca; lay eggs. Progressive: hairline, mammary glands (however, there are no nipples, the ducts of the glands open on the "milky" field of the mother's skin, the cubs lick it off). Body temperature is low (25-30 °C), largely dependent on the ambient temperature The platypus lives along the banks of water bodies, swims and dives well, feeds on aquatic invertebrates (insects, crustaceans, mollusks, worms). The cubs have milk teeth, in adults the jaws are toothless, flat. The paws have webs and claws. Eggs with a diameter of 15-20 mm, in a parchment-like shell, lay in a hole, incubate for 7-10 days
marsupials About 250 Australia, New Guinea, etc.; South and North America Primitive: the placenta is underdeveloped, the gestation period is very short, the presence of a bag on the stomach is characteristic, in which the development of the cubs ends. Progressive: live birth; mammary glands with nipples, coracoids fuse with shoulder blades. Body temperature around 36°C. Teeth are not interchangeable (corresponding to the milk teeth of higher mammals) There are insectivorous (marsupial mice, moles), predatory (marsupial wolves, marten), herbivorous (kangaroo, marsupial bear - koala)
Higher, or placental About 4000 All continents except Antarctica, as well as seas and oceans The embryo develops in the uterus, where, due to the fusion of two amniotic membranes, the placenta is formed, forming a spongy chorion; chorionic villi fuse with the epithelium of the uterus; give birth to well-formed cubs capable of feeding on mother's milk on their own. Have milk and permanent teeth There are insectivores, carnivores, herbivores; 17 orders in total (the main ones are insectivores, bats, rodents, hares, carnivores, pinnipeds, cetaceans, artiodactyls, equids, proboscis, primates)

Monotremes, or cloacals (platypus, echidna, prochidna), live only in Australia. They put aside quite large eggs with lots of nutrients. After fertilization, the egg stays in the mother's genital tract for a long time (16-27 days), at which time the embryo develops in it. The period of incubation or carrying the egg is short and does not exceed 10 days. Monotremes lack teeth. The intestines and urogenital organs open into the cloaca. There are no nipples. The shoulder girdle is similar to that of reptiles. Body temperature ranges from 24 to 34 °C. Paired oviducts (fallopian tubes) and the uterus pass into the urogenital sinus. The listed features indicate a significant primitiveness of the structure of cesspools and their proximity to ancestors common with reptiles.

Lower animals, or marsupials (kangaroo, marsupial wolf, marsupial mole, etc.), live in Australia and South America. They do not have a placenta (except for some species), the cubs are born underdeveloped and are born in a bag, hanging on the nipple (for example, a giant kangaroo weighing 60-70 kg gives birth to a cub weighing only 80 g the size of Walnut, other marsupials have even smaller newborns). Newborn marsupials independently crawl into the mother's pouch, where they find the nipple. As soon as the cub finds the nipple, the latter swells and fills the oral cavity of the newborn. The calf feeds on milk and lives in the mother's pouch from 60 days in small species to 250 days in large species. The brain of marsupials is primitive. There are two uteruses and two vaginas. Teeth, except for the front molar, are not replaced. Body temperature is not strictly constant, but higher than that of single passers.

The vast majority of modern mammals belong to the higher animals, or placentals. Their features are that the nutrition of the embryo occurs through the placenta. The cub is born more or less developed and can suck milk. The brain is well developed. There are two changes of teeth.

Modern placental are divided into 16 orders. The most important of them are: insectivores, bats, edentulous, rodents, carnivores, pinnipeds, cetaceans, ungulates, proboscis, primates. The order of insectivores, very ancient in origin, is distinguished by the greatest primitiveness of the structure. One of the most highly organized orders (although retaining many primitive structural features) are primates. Characteristic features of the main orders of mammals are given in table. 21.

There are suborders of lower primates, or semi-monkeys (tupai, lemurs, tarsiers), and higher primates. Among the latter, a group of broad-nosed (marmosets, howler monkeys, arachnids and woolly monkeys), narrow-nosed (monkeys, macaques and baboons) and anthropoid (orangutans, chimpanzees, gorillas) monkeys are distinguished. All groups of modern primates are characterized by a high level of specialization.

Apes are the most highly developed animals. They differ in the complex structure of the cerebral cortex, do not have cheek pouches, tail and ischial calluses. The appendix of the caecum is long (20-25 cm). They have four blood types, just like humans.

TO higher primates the family of people with the only modern species, Homo sapiens, also belongs. According to archaeologists, the region of human origin, apparently, was Africa. Morphologically, a person is characterized by an exceptional development of the brain, a weak development of the jaws and teeth, a strongly developed tongue and a chin protrusion. The hairline is reduced, the spine is straightened, the skull is on the spinal column from above, the legs end in an arched foot, the hand is a very perfect and versatile organ. A person owns articulate speech and is capable of very complex mental activity. The formation of Homo sapiens was associated with labor activity.

Table 21. Characteristics of the main orders of placental mammals
Detachment Number of species Main features Some representatives
in the world in the USSR
Insectivores About 370 38 The teeth are of the same type, sharply tuberculate. The anterior end of the head is extended into a proboscis. The olfactory region is best developed in the brain, the hemispheres are almost without convolutions Moles, hedgehogs, desmans, brown-toothed and common shrews
Bats About 850 39 The forelegs are modified into wings. The keel is developed on the sternum, the muscles that move the wings are attached to it. The auricles are large, complex; the auditory subcortical centers are very well developed. Many species navigate using ultrasonic echolocation Ushans, red vespers, flying dogs, flying foxes, vampires
rodents 2000 143 Strongly developed incisors do not have roots and constantly grow. There are no fangs. The molars have a large chewing surface covered with tubercles or ridges of enamel. There is usually a large caecum Squirrels, jerboas, beavers, marmots, muskrats, ground squirrels, mice, hamsters, rats
Lagomorphs About 60 12 They have two pairs of upper incisors, one of which is located behind the other Hares, rabbits, pikas
Predatory 240 45 The incisors are small, the fangs and carnassials are strongly developed - the last upper premolar and the first lower molar. In most species, the fingers are armed with sharp claws. Predominantly Carnivores Wolves, foxes, bears, arctic fox, sable, martens, raccoons, ermine, weasel, ferrets
pinnipeds 30 12 Both pairs of limbs are transformed into flippers, a thick leathery membrane is between the fingers. There is a thick layer of fat under the skin. Streamlined body, large Walrus, seals, fur seal, seals, sea lion
cetaceans 80 30 The forelimbs are transformed into flippers, the hind limbs are reduced. The body shape is torpedo-shaped. No hairline, ears. There is a caudal (in some species and dorsal) fin. Navigate with sound echolocation Dolphins, sperm whales, whales
artiodactyls 170 24 There are four toes on the feet, of which the second and third are well developed. On the fingers - horny hooves. There are no keys. The stomach in most species is complex - from several departments Pigs, elk, cows, deer, giraffes, antelopes, goats, sheep, bison, bison, yak, saiga, chamois, roe deer
Odd-toed ungulates 16 3 One (third) toe is well developed on the feet, usually with a hoof. There are no keys. simple stomach Zebras, tapirs, rhinos, donkeys, horses
proboscis 2 - Very large animals. The nose and upper lip form the trunk. Paired upper incisors form tusks Indian elephant, African elephant
Primates About 190 - Limbs of a grasping type, five-fingered, the thumb is mobile and in many can be opposed to the rest. Nails are developed on the fingers. There are teeth of all categories. The brain has a large volume and complex structure; eyes are directed forward. When walking, they rely on the entire foot Tupai, lemurs, tarsiers, marmosets, howler monkeys, monkeys, macaques, baboons, orangutans, chimpanzees, gorillas

Economic and medical importance of mammals

It is difficult to name any group of animals that would have such significance in the history of mankind and in the economy of the national economy as mammals. They were first domesticated by primitive man (he received from them food, raw materials for the production of clothing, shoes and draft power). Over time, hundreds of breeds of large and small cattle, pigs, horses were bred, which are of great economic importance.

Currently, there are various breeds of cows (dairy - Kholmogory, Dutch, Yaroslavl; meat and dairy - Kostroma, Simmental; meat - Kalmyk, Shorthorn) and sheep (Romanov, Karakul, Askanian and Caucasian fine-fleeced). One of the most important branches of agriculture is pig breeding. Especially valuable breed- steppe Ukrainian white pig, bred by the Soviet livestock breeder M.F. Ivanov. There are many breeds of domestic horses, in particular, Oryol trotters, Don, Arabian, English, Vladimir, etc.

Camels, buffaloes, yaks, donkeys, and deer are also used in the national economy. In the northern regions of Russia, reindeer breeding is an important branch of the economy; reindeer have long been domesticated there. Red deer are bred in park and hunting farms to obtain antlers - non-ossified horns containing pantocrine and other medicinal substances. For the same purpose, Far Eastern spotted deer and marals are bred. Deer and other wild ungulates are also a source of meat and skins.

Whales are important fish species. They produce margarine, lubricants, glycerin, gelatin, glue, soap, cosmetics and drugs (in particular, vitamin A from the liver). Meat, entrails and bones are used to make feed flour for pets, as well as fertilizers. A valuable product is sperm whale spermaceti. Marine whaling is regulated by international agreements, but the number of whales and sperm whales is noticeably declining. Currently, hunting for gray and blue whales, humpback whales and fin whales is prohibited by the International Convention. There is limited hunting for sperm whales, sei whales, bottlenose whales, pilot whales. Valuable objects of marine hunting are pinnipeds. Skins, seals, harp and Caspian seals are used as fur raw materials (young animals), as well as for the needs of the leather industry. The fur of fur seals is especially valued, which form large rookeries in Russia on the Komandorskie and Tyulenye Islands, in the USA - on the Pribylov Islands. Fat and meat of pinnipeds are also used.

The USSR ranks first in the world in the production of fur-bearing animals. The bulk of the fishery is made up of 20 species. The main commercial species of the forest zone are sable, squirrel, marten, ermine, foxes and hares, and the tundra - arctic fox and white hare, in the steppes and deserts - foxes, hares, ground squirrels, in river valleys - muskrat, water rat, otter, coypu (on South). About a third of furs are mined in the north of our country. Hunting for valuable fur animals is carefully regulated and carried out on a scientific basis, which also provides for the protection and breeding of animals. Particularly great successes have been achieved in increasing the number of sables and in the artificial resettlement of the beaver. The artificial resettlement of the sable to the forests of the Tien Shan, the Far Eastern raccoon dog and spotted deer to the European part of Russia has also been carried out. Some fur-bearing animals have been successfully acclimatized in our country, in particular, the North American muskrat, the South American nutria, and the American mink.

Some species of mammals (rats, mice, guinea pigs, etc.) are used as laboratory animals in biological and medical research and are bred in large numbers.

Many wild mammals are reservoirs for a number of vector-borne diseases. Ground squirrels, marmots, tarbagans and other rodents are a source of human infection with plague and tularemia, mouse-like rodents and rats with toxoplasmosis, epidemic typhus, plague, tularemia, trichinosis and other diseases.

Mammals also have great importance as consumers of harmful insects (for example, insectivores - shrews, moles, hedgehogs; bats - ears, red evening, etc.); some representatives of the predatory order - weasel, ermine, black polecat, pine marten, badger and others - feed on harmful rodents and insects. During the day, weasel gets 5-6 rodents, mainly red, gray and water voles, in summer it also feeds on click beetles. The badger feeds on mouse-like rodents and larvae of beetles, click beetles, weevils, and leaf beetles.

Some mammals bring great losses to the national economy. Many species of rodents (mice, voles, ground squirrels, rats) damage agricultural and forest crops, pastures, stocks in storages. Their harmfulness is increased by the fact that voles and mice are capable of mass reproduction. Marmots, ground squirrels, gerbils, some voles, mice and other rodents can store and spread pathogens of dangerous diseases in humans and domestic animals (plague, tularemia, foot-and-mouth disease, etc.), carriers of serious diseases feed on their blood - ticks, fleas, lice, mosquitoes, Some predatory mammals and bats store and transmit rabies pathogens. Many of these infections constantly exist in nature, that is, they have a natural focality. People and pets can get sick if they enter the territory of a natural focus and come into contact with sick animals or vectors. The theory of natural focality of diseases was developed by the outstanding Soviet zoologist Acad. E. N. Pavlovsky and his students. This theory has become the scientific basis for organizing the fight against these diseases.

Pests of agriculture and forestry are most often exterminated with the help of pesticides, but their use has Negative consequences- environmental poisoning, the death of many useful animals, etc. At present, in Russia, a bacterial preparation bactorodencid is produced in a semi-industrial way to control rodents. The drug is added to baits made from grain, chopped potatoes, bread crumbs.

Ferrets, foxes, jackals can cause some harm to poultry farming, however, in natural conditions they often feed on mouse-like rodents, and some also on carrion, etc. Wolves destroy many valuable wild and domestic animals, in some places it is necessary to limit their numbers, as well as the number of some others. predators, by shooting.

Fur farming

Fur farming in our country arose about 200 years ago, in the USSR this branch of animal husbandry began to develop intensively from 1928-1929, when the first specialized fur farms for the production of furs for export were created. Currently, fur farming is developing in three main areas: free, or island (this is how ungulates are mainly bred - deer, spotted deer, elk, which give antlers, skin and meat), semi-free (the main herd is kept in cages, young animals - in a limited area ) and cellular. The latter direction is the main form of modern industrial fur farming. On large fur farms they keep up to 100 thousand animals, and 85-90% of the total number of the main herd of females is mink of various colors. They also grow nutria, foxes, arctic foxes, sables, chinchillas, river beavers. As a result of the successful use of genetic breeding techniques, more than 30 types of colored minks, several types of colored foxes and blue foxes have been bred. In total, about 20 species of animals are bred in the world.

Mammal Conservation

Over the past century, more than 100 species of mammals have been completely destroyed on the globe; currently, about 120 species of mammals are under the threat of extinction. The problem of preserving and increasing the number of polar bears, tigers, snow leopard, bison, wild spotted deer, some species of whales and seals and other animals. For this purpose, back in the USSR, the Law "On the Protection and Use of the Wildlife" was adopted, in accordance with it, rare and endangered species of animals are entered in the Red Book of the USSR and the Red Books of the Union Republics. Shooting and trapping of rare and endangered species of animals is prohibited in our country, nature reserves, sanctuaries, and micro-reserves have been created where integral natural communities of animals are preserved.