Placental birds. Placental, like higher mammals

The vast majority of modern mammals, which fall into numerous and extremely diverse orders, belong to this subclass. However, all of them, unlike marsupials: 1) are deprived of a bag and marsupial bones; 2) the embryo develops, being connected with the mother using a real placenta, the cubs are always born more or less developed and can suck milk; 3) the brain has a highly developed secondary cerebral arch - neopallium, both halves of which are connected by the corpus callosum; 4) the body temperature in adults is high and constant; 5) as a rule, milk and constant tooth changes are well defined.

Due to the height of organization and the perfect psyche, the placental ones were able to spread not only throughout the land of the globe, but also throughout the oceans (cetaceans and pinnipeds), having successfully survived the struggle for existence with animals such as fish perfectly adapted to life in water and penetrated into air environment where they withstand competition with birds (bats).

The ancestors of placental mammals were the so-called pantotherium - small animals with three tubercle teeth that existed in the Triassic of the Jurassic period. The first placental mammals appeared at the end of the Cretaceous. These were primitive insectivorous animals, and from them, in turn, various orders of the considered subclass originated.

Detachment Insectivorous.This is the most primitive detachment of placental mammals. It includes small or small animals, characterized by continuous rows of pointed, poorly differentiated into groups of teeth, a small forebrain lacking in convolutions, a two-horned or two-parted uterus. Of the external signs of insectivores, a small mobile proboscis, with which the muzzle ends, is characteristic.

The limbs, as a rule, are five-fingered, armed with small claws and almost always stop-moving. The way of life is terrestrial (often digging), less often semi-aquatic, and in one group ( dull) - half-wood.

Insectivores are widespread in all parts of the world, excluding Australia and South America.

In the fossil state, insectivores are known from the Upper Cretaceous, i.e., they are the oldest of placental mammals. Currently, this detachment is represented by disparate, far-spaced groups, of which only shrews are widespread throughout the globe.

Within Europe and Siberia, numerous shrews  belonging to two main genera - shrew  and shrews; four species of hedgehogs, of which the most widespread common hedgehog; moles of which the most famous common mole, and muskrat.

Shrews resemble mice in appearance, but easily differ from them in the shape and arrangement of teeth, velvety fur and a sharp muzzle. They lead a very mobile lifestyle, living mainly in moist and humid places. Sometimes they run into houses. They are very predatory, they even attack small rodents that exceed their own size, although the main food of shrews is insects and worms, which bring significant benefits. However, in forestry, they can also be harmful by eating a lot of seeds of spruce, pine, birch that have fallen on the ground, which complicates the natural regeneration of the forest. In addition, shrews serve as hosts for the larvae and nymphs of ticks that store viruses that are dangerous to humans, support the existence of natural foci of a number of vector-borne diseases.

Most widely distributed common shrew  and water shrew,  or bill, which lives near the water and swims superbly with the help of its hind legs, trimmed with a fringe of coarse hair, and a tail pinched from the sides. To obtain relatively large prey (frogs, mammals), the bill helps with the toxicity of saliva, which, when bitten, gets into the victim’s wounds, weakens or even kills her. The American short tail shrew  the secret of the submandibular glands is poisonous, the duct of which opens at the base of the anterior incisors.

Distributed in the south of Western Europe and the Caucasus and Central Asia baby shrew  and taiga little shrewhaving a body length of about 4 cm -   the smallest mammals.

Hedgehogspossessing a peculiar ability to defend themselves by curling up, turning into a prickly ball, they are useful, destroying insects, rodents; they also catch lizards, snakes, frogs, ruin land nests of birds. These are the only ones of our insectivores that fall into hibernation.

Mole, widespread in the forest and forest-steppe strips of the European part of Russia and the Caucasus, is a burrowing underground animal, the whole structure of which is remarkably adapted for such a life: its body is bar-shaped, with a pointed wedge head, short but powerful front legs armed with strong claws, thick velvety fur without lint; tiny eyes have underdeveloped optic nerves, and the auricles are completely absent.

Muskratliving only in our Volga and Don basin is an aquatic animal. Its thick fur does not allow water to pass through, large hind limbs framed by a brush made of elastic hair, and a tail compressed from the sides and a scaled tail serve as organs for quick, agile swimming. Lives in deep holes, the outlet of which is located under water. It is highly regarded as a furry animal, but prey is now prohibited.

Certain groups of insectivores exhibit remarkable convergence with rodents; So, shrews  look like mice moles -  on mole rats hedgehogs  - partly on porcupine, African jumpers  galloping on one hind legs, on jerboas, and arboreal South Asian dull  - for protein. I must say that according to a different classification dull  - This is a family of semi-monkeys. However, new data confirm the close relationship of these animals with neither insectivores nor semi-monkeys. Therefore, it was proposed to separate them into a separate unit of Tupaya.

Sherstokryly detachment.This applies only wool wing, which surprisingly combines the features of insectivorous, bats and semi-monkeys and is thus a good example of a “prefab type”. It has the size of a winged wing with a cat and is distinguished by a wide hairy membrane covered with all four limbs and a tail. Woolwing is a real tree animal, which, thanks to the membrane, can make long gliding jumps, as if flying from tree to tree. It feeds on plant foods. Lives in the tropical forests of Southeast Asia and its neighboring islands. Fossil woolly wings are known only from the Upper Paleocene and Lower Eocene of North America.

Order Bats, or Bats.Bats have much in common with insectivores and can be considered as a special branch of the latter, adapted to flight. The forelimbs of bats are modified into true, but distinctive wings are perfect: all the fingers of the forelimbs, except for I, are very elongated, and between them, the sides of the body and hind limbs a thin, hairless membrane is stretched, which usually extends between the hind legs limbs, turn on the tail. In connection with the development of powerful muscles that lower their wings, a short keel is formed on the sternum, which serves to attach these muscles, and the clavicles achieve strong development.

They conduct nightlife and are guided on the fly by mainly reflected ultrasounds. By experiments, set at the level of modern technology, it was found that bats make not only ordinary sounds we hear - a squeak, but also ultrasounds with a frequency of 30,000 to 70,000 Hz in the form of individual pulses. The pulse frequency in this case varies depending on the distance between the animal and the subject. The reflected wave of these ultrasounds is also perceived by the hearing aid bats, i.e. they have a thin ultrasonic locator. They live more often in colonies, sometimes reaching enormous sizes.

This detachment, containing about 1 thousand species, splits into two well-separated suborders: winged  and real bats.

Suborder is the fruit-eating bats, or winged bats.Suborder contains one family krylans  about 250, for the most part, are very large species (up to 1.5 m wide) distributed in tropical regions of Africa, Asia and Australia. They are characterized, on the one hand, by a number of primitive features (not only the I, but also the II finger of the forelimbs is equipped with a claw, the ears have a structure typical of mammals); on the other, specialization traits: their molars, with flattened crowns, are adapted to nourish plant foods consisting of juicy fruits. In some places, winged birds are very serious pests of fruit stands.

Suborder real bats.The suborder includes all other types of order, comprising 16 families. These animals are characterized by small size, sharp teeth, adapted for feeding insects in a large number of species. The ears are large, peculiarly modified. In terms of speed and maneuverability of flight, many insectivorous bats are not inferior to swallows and swifts. Widely distributed throughout the world, but are especially numerous in the tropics and subtropics. Adaptive divergence due to food specialization is well expressed in these outwardly very similar animals. Many small species feed on nectar and pollen of flowering plants and insects found in cups of the same flowers. These are bilingual batsNew World (16 births), flower bats  West Indies and others. A number of plant species are adapted for pollination by bats. Soft juicy fruits eat many species. leaf-bearing bats. There are species that prey at low tide on marine mollusks inhabiting the littoral, species that grab insects and small mammals from the water (bulldog mouse); some other than insects eat frogs, lizards, small birds and mammals. Vampires  feed on the blood of large mammals, causing them small wounds. This is done so imperceptibly that animals usually do not wake up, as vampire incisors are extremely sharp, and saliva has anesthetizing (analgesic) and anticoagulating (anti-clotting) properties. Leaking blood vampires lick. Vampires are the keepers of the rabies virus. In some years, vampires infect tens of thousands of cattle and horses, which must be destroyed in order to eliminate epizootics.

Insectivorous bats are mostly useful, as they destroy many harmful insects, including vectors of infections. In large caves, which provide shelter to huge colonies of insectivorous species, for many centuries, whole deposits of guano accumulate - a very valuable fertilizer. Narrow gauge railways are laid to some caves for the convenience of exporting guano.

In our country, there are about 40 species belonging to 3 families (smooth-nosed, folded, horseshoes  and many other births). The bulk - 32 species - belongs to the family smooth-nosed, several types horseshoe found in the south of our country. Most bats from the northern regions fly away for the winter. Part spends the winter in deep hibernation. Mating occurs both in spring and autumn, before hibernation. In the latter case, spermatozoa remain in the genital tract of the females until spring, when they fertilize the eggs.

A typical representative of smooth-nosed - ushana, widespread throughout the territory and characterized by extremely large ears.

Detachment Toothless.This small but extremely peculiar unit includes sloths, anteaters  and armadillos.  They are characterized either by a complete absence of teeth (anteaters), or by their simplified structure: the enamel on the teeth is absent, the roots are undeveloped, the shape of all teeth is more or less homogeneous, and usually there is only one change of teeth. On the last thoracic and lumbar vertebrae there are completely peculiar accessory joints. The number of fingers reveals a tendency to contract, but some of them are extremely developed and armed with powerful claws. Along with extreme specialization, tootheds possess a number of very primitive features. The main ones are the weak development of the hemispheres of the forebrain, which are almost devoid of grooves, and the large coracoid, which only in the late stages of development merges with the scapula. All non-tootheds are very characteristic of the fauna of South America.

Sloths  - purely woody animals that feed on leaves and spend their whole lives on trees in a suspended position with their backs down. In this regard, the fingers, together with the claws, form hooks, as it were, with the help of which the animal hangs or moves slowly. The ribs supporting the insides are widened, and the hair on the body, and the opposite of all other animals, has a pile directed not to the abdomen, but to the ridge. The only way of self-defense of these harmless animals is to go unnoticed, which is facilitated by lower algae that settle in their long coarse fur and give it a green color.

Anteatersreferred to as great anteaterreaching 1.3m length ,   leading a terrestrial life, as well as small tree forms with a tenacious tail, are characterized by a long tube-shaped muzzle, a toothless mouth and a very long sticky tongue, which adhere to the ants and termites that make up the main food of these animals.

Armadillos- the only large group of modern edentulous. These are terrestrial, well-digging animals, the upper side of the body of which is covered with bony and overlying horn shields. The shields are movably connected to each other so that the animal can curl up in a ball. The teeth are numerous, more or less homogeneous and have the shape of sharp cones. They feed on a variety of animal and plant foods.

Although these three modern families are very different from each other, in the fossil state there, in America, numerous non-toothed ones were found, in particular slow movingconnecting sloths with anteaters, on the one hand, and with armadillos, on the other. Of them megaterium  reached the size of an elephant and ate, like modern sloths, leaves, but, of course, could not climb trees, and, using its great strength and weight, apparently bent them to the ground. This animal survived to the beginning of the modern geological period, and, according to all reports, it was still found by a primitive man. Also noteworthy fluterterium  growing from a bull, from which even pieces of skin covered with hair were preserved, with traces of cuts made by a person. It is possible that a man kept him domesticated for the sake of meat. Finally, the fifth family of edentulous - giant armadillos, or glyptodontsreaching almost 4 m in length. They differed from modern armadillos along with other signs in that the bony shields of their carapace fused immobile, forming something similar to the back shield of turtles.

Squad of the Lizards.Pangolins  characterized by a horny scaly cover, individual scales of which overlap each other, like the scales of a fir cone. They feed mainly on ants and termites. There are no teeth, the tongue is very long and sticky; the stomach, into which the pebbles are swallowed, is lined with a horn-like shell, and food is crushed in it (analogy to the muscular stomach of birds). Thus, the dinosaurs show a great resemblance to anteaters. However, the similarity is purely convergent, due to the same food - ants and termites - and the method of its extraction - by digging up the solid structures of these insects. As recent studies have shown, there are no signs that indicate a kinship between the dinosaurs and American edentulous.

The origin of the lizards is completely unclear, since the forms found so far belong to the only modern genus. Several closely related species of dinosaurs are found in Africa and South Asia. Among them are both terrestrial and woody forms.

Squad Rodents.Rodents form the richest order of mammals: the total number of modern species exceeds 2800, they are combined into 30 families - which is about 1/3 of all living species of mammals. They are characterized mainly by the structure of the teeth. Incisors, which on each side of the upper and lower jaws are only one each, achieve extreme development, are devoid of roots and grow throughout life. There are no fangs, and the incisors are separated from the indigenous by a wide toothless gap - diastema. Molar teeth used to grind solid plant foods have a wide chewing surface; it is covered with blunt tubercles or low ridges of enamel, or, finally, completely smooth. The muzzle, unlike the insectivores, is blunt. The hemispheres of the forebrain are relatively small and devoid of convolutions. The sizes are small or medium. The way of life is terrestrial, burrowing or arboreal, less often - aquatic. Food is predominantly or exclusively vegetable.

With the exception of the extreme polar regions, rodents are distributed over the land of the globe.

The biological feature of rodents is their ability to breed rapidly, which is due to the large number of cubs in the litter, a significant number of litters per year and early maturity. Due to this feature, in favorable years, many rodents extremely increase in number, after which mass death usually follows.

The large number of rodents determines their great importance in nature (in three directions): 1) due to burrowing activity they play a significant role in soil formation; 2) destroy a huge amount of plant feed; 3) serve as a very important food base for carnivorous mammals and birds. Rodents are very important in the human economy. Many of them, for example voles, mice, hamsters,  most gophers  are the most serious pests of crops and food stocks - mice, rats.Some like marmots, gophers, gerbils, rats, serve  custodians and carriers of infectious diseases, in particular the plague. Individual species, primarily squirrel, beaver, muskrat,  belong to the most important hunting animals.

Rodents, according to the latest systematics, are divided into 3 suborders: squirrel-shaped, porcupine  and mouse-like.

The suborder is squirrel-shaped.Representatives of this huge suborder have only one incisor in each half of both the lower and upper jaw. The suborder includes a number of families, the most important of which are squirrel and beavers. The squirrel family includes squirrel, chipmunks, gophers, groundhogs.  The flying squirrel family adjoins here. Squirrels, which include about 200 species, are typical forest animals adapted for climbing trees (tenacious claws, vibrissae located on the chest, which is associated with their manner of “hugging” the trunk when climbing) and jumping from branch to branch (long , fluffy, combed on two sides tail serves to control flight when jumping).

Common squirrel  It is distributed throughout the forest and forest-steppe zones of Europe and Siberia and forms the basis of our fur trade. Its main food is coniferous seeds and nuts. In addition, it feeds on tree buds, berries and mushrooms, which it dries by bumping into a branch. Only in the most severe frosts does a squirrel not leave its nest for several days - a “guy”, which is usually placed high on a tree, woven from branches, equipped with two outlet openings and has a spherical shape.

Chipmunk  - a striped small animal, smaller than a squirrel, it leads a land-woody lifestyle and is widespread in the Siberian taiga. This is partly a pest, partly a low-value commercial form.

Gophers, of which there are many species within the former USSR, are mostly steppe, partly mountain animals. They live in colonies in burrows, hibernate for an unfavorable time. Many gophers are serious pests of crops. But the largest of them is yellow gopher, living in the Volga, Kazakhstan and Central Asian steppes and semi-deserts, does little harm, as it avoids cultivated land, and at the same time it belongs to important commercial species. It is interesting in that when the vegetation burns out, it falls into summer hibernation, passing without interruption into winter hibernation, so that only in the year it is awake in places for 3.5-4 months.

Systematically close to gophers groundhogs, differing from them mainly in large sizes (with a cat) and underdeveloped cheek bags. They live in our colonies in the mountains of Central Asia and Siberia right up to Kamchatka and in the steppes of Kazakhstan and Transbaikalia. These are important game animals caught for the sake of fur and fat, which are accumulated in large quantities before hibernation. So-called slender gopherliving in the deserts of Central Asia, is the closest relative of African ground squirrels and, although, in general, similar to real gophers, it differs from them in that it does not fall into hibernation completely, puts on long fur for this time of year and leads a solitary lifestyle. Eating cereals, it contributes to the dispersal of sand, which does significant harm in some places, but at the same time it belongs to fur animals, the fishing of which begins to develop.

Our flying squirrel, whose numerous relatives inhabit tropical forests, is widespread in the forests of the European part and throughout Siberia. Due to the wide fold of skin stretched between the front and rear legs and sides of the body, she can make long jumps while planning. The fur is of high quality, but the skin is so thin that it depreciates the skin. Leads a nocturnal lifestyle; feeds on tree buds, bark and seeds.

The beaver family includes only 1 species - river beaver. This is a large rodent, having a flat tail, covered with scales, a thick fur, impervious to water and hind legs equipped with swimming membranes. He lives families in burrows or arranges special constructions from branches and silt - the so-called "huts". Together, beavers make dams from branches and tree trunks, blocking them with rivers and, thus, keeping water at a constant level, and also break long channels through which trunks are fused. All these actions are carried out by them, as thorough research has found out, instinctively. Once a beaver was widespread in Ancient Russia and was harvested in large quantities for valuable fur and even more valuable before the “beaver stream", which is produced by the musk glands at the root of the tail. Currently, the beaver has been preserved mainly in Belarus, in the vicinity of Voronezh and in the Northern Urals. Thanks to the adopted measures of protection and artificial resettlement, the beaver is now rapidly increasing in number. Outside of Russia, beavers in significant numbers are found only in Canada and in the northern part of the USA, where they live close to ours. canadian beaver.

Suborder porcupine.Families of porcupines and igloshersts close to them are distinguished by the presence of long, sharp needles covering the upper body of the animal. While porcupines are terrestrial animals with a short tail, igloosers lead an arboreal life and are equipped with a long, tenacious tail. We have only 1 species of porcupine, which lives in the southeastern part of Transcaucasia and in the foothills of Central Asia and in some places causes serious harm to agricultural, mainly melon, crops. Contrary to popular belief, a porcupine cannot throw out its needles, but, defending itself, with sharp movements backwards, tries to stick them into the enemy, and, resting on the ground, the needles often fall out and bounce to a considerable distance.

The guinea pig family, which belongs exclusively to South and Central America, contains the largest rodent - capybara, with a medium-sized dog, and a pet guinea pig, as well as a number of other rodents. The guinea pig (its original name was an “overseas” pig) was domesticated by the ancient Peruvians and is now kept everywhere as a laboratory animal.

The eight-tooth family is also South American. Refers to him nutria,  or beaver rat, - a large water rodent with valuable fur. It is acclimatized in places in Western Europe, the Caucasus, and Central Asia; recently divorced in the middle lane; her fur is often known as “monkey”.

Suborder mice-like.The suborder mice are 3 very numerous superfamilies: 1) mouse-like, 2) jerboa  and 3) dormouse.

Family jerboas  combines quite a few desert-steppe and desert animals, leading a strictly nocturnal lifestyle. They have very short front and very long hind limbs and a tail, usually ending with a flattened brush. Thanks to their strong hind legs, they can jump extremely fast, adjusting their tail movement, and cover large spaces in search of food, which is very important in the desert with its sparse vegetation. About 16 species of jerboas live in our steppes and deserts. Their significance for the national economy is small.

Family mole rats characterized by a number of features associated with digging life. In mole rats, the embryonic eyes are hidden under the skin, the auricles have atrophied, the body is squamous, the fur is short, velvety, the head is wide, spade-flattened, the nose has keratinized skin forming a pointed rib. In contrast to the mole digging with its front paws, mole rats dig the ground with their very large wide incisors, which, thanks to the ability of the lower jaw to move to the additional posterior articulated surface, act like a hoe (in this regard, their limbs are not very developed), and throw the earth out with their heads. In our country, mole rats are found mainly in the Black Sea-Azov steppes, where they are pests of agriculture.

Family mouseto which the mouse, rats, hamsters, voles, gerbils  and others are the most extensive family of rodents. Due to the large number of individuals, this family plays a large role in biocenoses and is of great economic importance, since it includes the main agricultural pests, which multiply in huge numbers during the years of “mouse adversity”. The most famous representatives: house mouse, forest  and field mouse  and pasyuk rat, settled after a man around the globe; common hamsterinhabiting the steppes and fields of Europe, the north of Kazakhstan and Western Siberia, and common vole, which, like all voles, has a blunt muzzle, short ears, small eyes and a relatively short tail, close to Arctic voles lemmings; muskrat  - a fairly large rodent, leading a semi-aquatic lifestyle and is the main commercial species of North America. The muskrat is currently successfully acclimatized in Eurasia.

Detachment Hare.It is characterized by the presence in the upper jaw behind large incisors of a pair of small additional incisors. Recently, double-incisors are singled out in a special detachment. Only 2 families belong to hare-like: pika  or senostavok, and hares.

The family of pikas combines small, larger rats, tailless animals with rounded ears and hind limbs, somewhat longer than the front ones. Mountain and steppe animals of the northern hemisphere. We live in the Urals, in the mountains of Central Asia and Siberia, as well as in the Volga, Kazakhstan and Transbaikal steppes. They don’t hibernate for the winter. Gained widespread fame for gathering stocks of dried grass for the winter.

The hare family includes both rabbits and rabbits. We have 4 species of hare: harecommon in the tundra and forest belt, hareinhabiting the steppes of Europe, from where it somewhat enters Western Siberia and the Caucasus, tolaifound in Central and Central Asia, manchu harefound only in the South Ussuri Territory. For the winter, the hare becomes completely white, only the ends of his ears remain black all year round; the more southern grouse only partially whitens at this time of the year, while the last 2 species of hares retain a grayish-brown color for the winter. Roe is much larger than the white hare. The paws of the whale are wide and fluffy - an adaptation to running on loose forest snow, the paws of a brown grouse are narrow, knocked down - an adaptation to running on a solid snowy steppe infusion. Unlike rabbits, hares live alone, almost do not dig holes, arranging only digging, and their cubs are born fully developed, covered with thick fur. Hares are a brown hare, and especially a white hare - important game animals.

The squad is predatory.Predators are distinguished by large sharp fangs, tuberous, usually with sharp, cutting edges, molars and small weak incisors. The posterior pseudo-root maxilla and the first true-root lower jaw are usually distinguished by their size and are called predatory teeth. The claws are well developed, sometimes retractable, the collarbone is rudimentary. The hemispheres of the forebrain are highly developed and covered with convolutions.

This squad is divided into 7 families: wyverns, hyenas, cats, martens, bears, raccoons  and dogs.

The Viverra family unites the most primitive modern predators. The sizes are small or medium. The body is slender, elongated, with relatively short legs and a long tail. Distributed in South Asia, southern Europe and Africa. In our fauna are absent. Typical representatives: african wiverra  and mongooses.

The hyena family includes typical scavengers with weak legs (they do not pursue prey), extremely strong jaws and powerful predatory teeth, which easily bite bones (if they find their rare food - carrion, they need to use it as fully as possible). Hyenas, of which there are only 3 species, are common in South Asia and throughout Africa. In the countries of the former USSR, only   striped hyenafound in Transcaucasia and in southern Central Asia.

The cat family is the most specialized predator with retractable claws (i.e., the final phalanges on which the claws sit, bend upward when walking), a short muzzle and extremely strong predatory teeth. Vision is especially well developed. A characteristic way of hunting is to sneak up and then a sudden jump. Distributed throughout the continent, excluding Australia.

Within the former USSR there are several large cats and a number of small ones. The largest cats are tiger, which we meet in places in Central Asia and the Far East, a typical beast of South Asia and the African a lionpenetrating only into South-West Asia.

The commercial value of cats is small; comparatively more important lynx, which is widespread in all forest areas, but everywhere is quite rare. The wild ancestor of a domestic cat is considered bulan catliving in Egypt. It was tamed by the ancient Egyptians, but only in the Middle Ages came to Europe.

The family of cunyas is very diverse, moderate or small sizes and relatively short finger-extending limbs are typical for individuals. Distributed throughout the continent, excluding Australia. The most important representatives: pine marten  and stone, sable, ferrets, mink, ermine, affection, otter, badger, wolverine. These are fur trade animals. Ermine and weasel are of general biological interest in that for the winter they change their summer brown fur to white, under the color of snow.

The family of bears is characterized by the fact that these are animals of heavy build, usually very large in size, when moving they are reared on the whole foot (stop-walking), the tail is very short. Within Russia there are 3 types: brown bearcommon in all forest areas; relatively close to him the black,  or himalayan bearfound in our Ussuri region, and polar bear  - A resident of the floating ice of the Arctic Ocean. Brown bear is a land animal that feeds mainly on invertebrate animals and plant foods, although in some places it seriously harms cattle breeding. A lair is arranged on the ground, usually under a fallen tree. European individuals rarely exceed 300 kg, but huge Kamchatka ones weigh up to 600 kg or more. A black bear is a more arboreal animal that arranges its den in hollows. The polar bear, which feeds mainly on seals, is the largest of modern predators; its individual individuals reach a weight of almost 1000 kg. It is exterminated off the European coast, but not infrequently off the coast of Siberia.

The raccoon family is close to bears. Typical Representative - american raccoonhaving very valuable fur. It differs from bears in smaller size, long tail, even more omnivorous and more arboreal way of life. Currently, it is being acclimatized in our country in Central Asia (forests of eastern Ferghana) and Azerbaijan.

The canine family unites numerous representatives characterized by medium sizes, strongly developed long legs, adapted for running. The sense of smell is especially well developed. The main way of hunting is to drive prey. Distributed across all continents. Of those living in Russia, foxes, arctic foxes, and raccoon dogs deserve special attention. Fox  distributed throughout the European part of our country and in Siberia and together with the squirrel forms the basis of our fur trade; forms many geographical races (subspecies). Valuable silver-black foxes do not represent a particular geographical race, but are found as a rare exception; Now they are bred on farms. Arctic fox  - a typical resident of the tundra, wearing fluffy white fur for the winter (some individuals with a gray color in winter fur are known as “blue” Arctic foxes and are especially highly valued). This is the main fishing animal of our Far North. Raccoon dog, which received its Russian name for its external resemblance to the American raccoon, is found in our Ussuri Territory. This is the only representative of the canine, falling into a winter dream. It has not bad fur and is now acclimatized in many areas of the CIS. Wolf  widespread throughout Eurasia, the terrible pest of livestock (a controversial issue), subject to complete destruction. Domestic dogs originated from the wolf.

Detachment Pinniped.Pinnipeds, which include eared seals  (eg, fur seal), walruses  and numerous earless  or real seals are predators adapted to aquatic life, with which they are sometimes combined into one squad. Pinnipeds are characterized mainly by an elongated, valky body, paired limbs are modified into swimming flippers, teeth have a more or less uniform conical shape (walruses are an exception), the auricles are underdeveloped, the tail is very small; under the skin, in which, as in a bag, the body is enclosed, lies a powerful layer of fat, which reduces heat transfer and facilitates the specific gravity of the body. The eyeball has a flattened outer surface, and the pupil is capable of very strong expansion (which is important for underwater vision - in an environment where there is little light). For weeks and months, pinnipeds live in the water, resting and getting enough sleep on its surface. Only in water do they feed, and swallow the whole food without chewing it (the uniformity of their teeth is associated with this), and only walruses crush the shells of the mollusks that make up their main food with their teeth. On land, pinnipeds are quite helpless and move along it with difficulty; but for the birth of calves, their milk feeding, for mating and molting, pinnipeds need to stay on a solid substrate in air: at this time, pinnipeds crawl out onto land or on ice (depending on the type of animal) and spend here weeks, sometimes months.

Pinnipeds are divided into 3 families: eared

General characteristics of the class mammals. Features of placental development.

Characteristic of the subclass higher animals. The main features of higher animals.

Characteristic of the subclass lower animals.

Includes one squad of marsupials (Marsupialia). These mammals in their organization are superior to cloacal. Nervous, muscular, circulatory and other systems in them are better developed. Body temperature is higher (up to 37 ° C) and is subject to less fluctuations than cloacal ones. The reproductive system, in connection with live birth (although primitive), has also become more complicated, and the genitourinary tract is separated from the posterior part of the intestine, i.e., they lack cloaca. Milk is secreted through the nipples.

The male reproductive system is close to that of higher mammals. The copulative organ serves not only to remove the seed, but also urine. The middle parts of the female reproductive tubes turned into the uterus, where the development of the embryo takes place, and the backs become vaginas. Consequently, in lower animals, in contrast to higher mammals, two vaginas (in some species, even a third is formed). Accordingly, the copulative organ of males is bifurcated at the end.

In most marsupials, the placenta does not develop, and in other species it is very primitive. Therefore, the embryos do not receive enough nutrition in the uterus and the cubs are born underdeveloped and very small. They are independently selected from the uterus and attached to the nipples, but for some time they can not suck on their own, milk enters their intestines due to the contraction of the muscles of the nipples. The mother has grown up the young, some time on the back. However, in most species, females have a bag on their belly where newborns move on their own and in which their gradual development to a fully formed state lasts much longer than in the uterus. So, for example, in a giant kangaroo, whose height is about 2 m, the embryo is in the uterus for 39 days, and in the bag for more than 7 months. The length of the embryo when it leaves the uterus is not more than 25 mm. The number of pups in different species ranges from one to 7-8 or more, but the number of nipples in multiple species is less than that of newborns, and those that do not have time to attach to the nipples die.

Marsupials cannot be considered as direct ancestors of the placental, but in their organization they are close to those extinct primary viviparous mammals that gave rise to placental.

Placental includes all domestic mammals. From the highest group of placental - monkeys - a man descended. In the infraclass 17-18 modern units.

In higher mammals, in comparison with the two previously considered groups - cloacal and marsupials - the whole organization became more complicated. It was in placental animals that the nervous system reached its highest development, especially the forebrain cortex and the associated high ability to adapt to changing environmental conditions and the beginnings of rational nervous activity. The same should be said about the system of organs of movement, about the respiratory, circulatory, digestive and other systems. The body temperature of the placental is significantly higher than that of cloacal and marsupials. It is maintained, as a rule, at the same level, which indicates a high metabolic rate and complex thermoregulation. The most perfect form of live birth, characteristic of placental, ensures their embryonic development in the most favorable conditions. The care of the offspring (feeding with milk, protection from enemies, etc.) is better developed in higher mammals than in any of the animals.

In addition to feeding offspring with milk, a number of signs are characteristic of mammals; some of them are found in other groups of vertebrates, some are not characteristic of all species of mammals, and only some of these signs are unique (in other words, we are now talking about distinctive features typical  mammals). The most important of these features:

· Live birth (except for representatives of the first-born subclass);

· True homoyothermy (warm-bloodedness; the exception is the rodent naked mole rat);

· The presence of hair (wool), sweat and sebaceous glands;

· A high level of development of the nervous system, which provides a flexible response to environmental influences;

· A special type of brain structure (including the strong development of the forebrain, the transition to it of the functions of the main visual center and the control center of complex forms of behavior);

· The presence of three auditory ossicles of the middle ear (modified bones of the lower jaw), the external ear canal and the auricle;

· Heterodontic (differentiated into incisors, fangs, pre-radical and molar) teeth sitting in the cells (alveoli) of the jaw;

· Seven vertebrae in the cervical spine, the skull is attached to the first of the two by the occipital condyles;

· Four-chamber heart; one (left) aortic arch;

Alveolar structure of the lungs;

· Nucleated red blood cells.

Mammals are a highly organized class of chordate animals. Its representatives have populated all living environments, including the land surface, soil, sea and fresh water bodies, and surface layers of the atmosphere. The characteristic features of their organization are as follows:

1. The body is divided into a head, neck, trunk, paired fore and hind limbs, tail. The limbs are located under the body, due to which it is raised above the ground, which allows animals to move at high speed.

2. The skin is relatively thick, strong and elastic, coated hairline  well-retained heat generated by the body. In the skin are located sebaceous, sweaty, milky  and odorous glands.

3. The cerebral region of the skull is larger than that of reptiles. The spine consists of five sections. There are always seven vertebrae in the cervical region.

4. Musculature is represented by a complex system of differentiated muscles. There is a abdominal muscle septum - diaphragm.  Developed subcutaneous musculature  provides a change in the position of the hairline, as well as various facial expressions.  The types of movement are diverse: walking, running, climbing, jumping, swimming, flying.

5. The digestive system is highly differentiated. Saliva contains digestive enzymes. The teeth on the jaw bones sit in the holes and are divided by structure and purpose on cutters, fangs  and indigenous.  In herbivorous animals, the cecum is significantly developed. Most cesspool is absent.

6. Heart four-chamber  like birds. There is a left aortic arch. All organs and tissues of the body are supplied with pure arterial blood. Strongly developed spongy substance of bones, red bone marrow  which is a blood-forming organ.

7. Respiratory organs - lungs  - have a large respiratory surface due to alveolar  buildings. In the respiratory movements, in addition to the intercostal muscles, it is also involved diaphragm.  The intensity of vital processes is high, a lot of heat is generated, therefore mammals - warm-blooded  (homoyothermal) animals (like birds).

8. Organs - pelvic kidneys.  Urine is excreted through the urethra.

9. The brain, as in all vertebrates, consists of five sections. Especially large sizes cerebral hemispheres  covered bark  (in many species sinuous) the cerebellum.  The cortex becomes the highest part of the central nervous system, coordinating the work of other parts of the brain and the whole organism. The forms of behavior are complex.

10. The organs of smell, hearing, sight, taste, touch have a high resolution, which allows animals to easily navigate in the environment.

11. Mammals are dioecious animals with internal fertilization. The embryo develops winding  (for most). Food and gas exchange occurs through the placenta. After birth, the cubs are fed milk.

The most highly organized mammals are subclass placental  animals, or real animals. Their development completely occurs in the uterus, and the membrane of the embryo fuses with the walls of the uterus, which leads to the formation of the placenta, hence the name of the subclass - placental. It is this method of embryo development that is the most perfect.

It should be noted that mammals have well-developed offspring care. Females feed the young with milk, warm them with their bodies, protect them from enemies, teach them how to look for food, etc.

Subclass Placental. Egg Type Very small are devoid of nutrients. Embryo development - In the uterus, with the placenta. The mammary glands open on the nipples located on the ventral side of the body. Dental System Dairy and Permanent

Predatory

7th grade biology

Slide 2

§ 54. Origin and diversity of mammals Questions

1. List the similarities between mammals and reptiles.

2. What features of mammals are more progressive in comparison with reptiles?

3. Why did the bestialist reptiles get such a name?

4. Confirm with examples the widespread and high numbers of mammals.

5. Tell us about the origin of mammals.

6. What are the features of the structure and activity of the first animals?

7. Tell us how the cub of a marsupial animal develops (on the example of a kangaroo).

Slide 3

The vast majority of species (more than 4 thousand) of modern mammals, distributed throughout the globe, belong to the highest (placental) animals. Placental mammals in a single group combine the following common features. They have a well developed cortex of the forebrain hemispheres, the placenta always develops, and no brood bags.

Slide 4

• The nipples of the mammary glands are well developed, their number corresponds to the number of cubs. The young ones themselves suck milk. Adult placental body temperature is high and constant.
• Placental, or Higher, animals - a thriving and large group of mammals, consisting of 17-19 orders. The most important of them are as follows.