The external structure of mammals. Structural features and behavioral features of mammals Structural features and lifestyle of mammals

Outwardly, mammals are very diverse, their body structure depends on environmental conditions and lifestyle. Mammals have a head, neck, torso with two pairs of limbs, and a tail. The head has a mouth, nose, eyes, ears. The mouth in mammals is limited by soft mobile lips, which in childhood are involved in sucking milk, and later in capturing food. The eyes are protected by developed eyelids. Eyelashes are located along their edges. The nictitating membrane in mammals is underdeveloped.

Unlike amphibians and reptiles, the limbs of mammals are located under the body, so it is elevated above the ground.

The body of mammals is covered with strong and elastic skin. It contains the base of the hair. There are long thick guard hairs and short soft downy hairs. Hard long hair - vibrissae - is especially distinguished. As a rule, vibrissae are located on the head (the so-called "whiskers" of animals), on the lower part of the neck, on the chest. The structure of various mammalian systems is discussed in more detail in the table below.

The figure below shows the external structure of mammals (for example, a rabbit)

Features of the structure of mammals

The structure of mammals	Features of the structure of mammals
body integuments	Skin (strong and elastic, there are sebaceous and sweat glands); Hairline (consists of coarse guard hairs and soft thin undercoat hairs growing from hair follicles in the skin); Claws, nails, or hooves at the ends of the fingers
	1. Skull (brain and facial) 2. Spine - 7 cervical vertebrae; 12-15 chest (ribs are attached to them, connected in front to the sternum, forming chest), 2-9 lumbar vertebrae, 3-4 sacral, caudal vertebrae (the number depends on the length of the tail) 3. Belt of the forelimbs (two shoulder blades and two collarbones) 4. Belt of the hind limbs (three pairs of fused pelvic bones) 5. Skeletons of limbs (structure depends on living conditions)	1. Brain protection, capture and grind food 2. Body support. 3. The connection of the forelimbs with the spine. 4. Connection of the hind limbs with the spine
	The muscles of the back, the girdles of the extremities and limbs are especially developed.	Implementation of various movements
Digestive system	oral cavity (has teeth, tongue, salivary glands) -- "pharynx --> esophagus --> stomach --" intestines (thin and thick sections and rectum, the ducts of the pancreas and liver flow into it) -- "anus.	Grinding, digestion of food, absorption of nutrients into the blood
Respiratory system	Nasal cavities, larynx, trachea, two lungs. Breathing with the diaphragm.	Oxygenation of the blood, removal of carbon dioxide
Circulatory system	Four-chambered heart, two circles of blood circulation.	Metabolism of cells with blood.
Selection	Kidneys (one on each side of the body) --» ureters (from each kidney) --» bladder(one) --» urethra.	Removal of excess water and decay products
Nervous system	1. Brain - on the cerebral hemispheres of the forebrain there is a cortex with convolutions (associated with more complex behavior than in other animals); the cerebellum is well developed (associated with the coordination of more complex movements) 2. Spinal cord.	Movement control, unconditioned and conditioned reflexes; perception and conduction of signals
sense organs	The degree of development of each of the sense organs depends on the lifestyle of the animal.
Behavior	Complex, reflexes are easily formed, providing quick adaptation to changing environmental conditions
reproduction	All are dioecious, most (except for oviparous ones) bear cubs in a special organ - the uterus, and the embryo is attached to the wall of the uterus by the placenta (through the umbilical cord). Pregnancy is the process of intrauterine development of the fetus. The cubs are fed with milk produced in the mammary glands (milk is a mixture of proteins, fats, carbohydrates, vitamins, mineral salts and water necessary for the cub). Show concern for offspring.

The figure below shows the internal structure of mammals.

FEDERAL AGENCY FOR EDUCATION

STATE EDUCATIONAL INSTITUTION

HIGHER STATE EDUCATION

"NOVOSIBIRSK STATE PEDAGOGICAL UNIVERSITY"

FACULTY OF PRIMARY SCHOOL

Discipline: Zoology

Structural features and behavioral features of mammals

Performed:

Vashchenko Elena Gennadievna

Novosibirsk 2010

Introduction

General features of mammals

Features of the structure of mammals

Features of the behavior of mammals

Interspecies aggression

Intraspecific aggression

Conclusion

Bibliographic list

INTRODUCTION

Zoology - scientific discipline that studies animal world, a major part of biology. According to the objectives of the study, zoology is divided into a number of disciplines: systematics, morphology, embryology, animal genetics, zoogeography, etc. According to the objects of study, protozoology, which studies protozoa, invertebrate zoology, and vertebrate zoology, is distinguished. TO last object research and applies theriology, engaged in the study of mammals.

The emergence of mammals became possible as a result of the formation of a number of large aromorphoses, which reduced the dependence of animals on changes in the external environment. Mammals evolved from ancient reptiles at the very beginning mesozoic era, i.e. earlier than birds, but the development that led to the modern wealth of forms of this class of vertebrates refers to Cenozoic era, after the extinction of large reptiles.

I decided to talk about mammals, because. this is the most highly specialized group of land animals. There are currently over 4,000 species of mammals.

In the first chapter of the abstract, I will give an overview of the general features of mammals that distinguish them from other animals, then I will describe the features of their structure and behavior. On the features of the behavior of mammals, I will dwell in more detail, because. this topic is very interesting and fascinating, but it is not disclosed in the biology textbook.

COMMON FEATURES OF MAMMALS

Mammals - warm-blooded vertebrates from the group of amniotes. As I said, this is the most highly specialized group of land animals, which are distinguished by the following progressive features.

Highly developed central nervous system and sensory organs. The cerebral cortex appears, formed by gray matter, which ensures a high level of nervous activity and complex adaptive behavior.

Thermoregulation system, providing a relative constancy of body temperature.

live birth(except for oviparous ones) and feeding the cubs with mother's milk, which ensures the best safety of the offspring.

Mammal organization height It is also expressed in the fact that all organs in them reach the greatest differentiation, and the brain of the most perfect structure. The center of higher nervous activity is especially developed in it - the cerebral cortex, consisting of gray medulla. Due to this the reactions and behavior of mammals reach exceptional perfection. This is facilitated by very complex sensory organs, especially hearing and smell. The differentiation of teeth into incisors, canines, and molars also contributed to the rapid progressive development of mammals.

A huge role in the development of this group was played by the acquisition warm-bloodedness, i.e. constantly high body temperature. It arises due to: a) unmixed blood circulation, b) enhanced gas exchange, c) thermoregulatory devices

Unmixed circulation, as in birds, is achieved by a four-chambered heart and the preservation of only one (left) aortic arch in animals. The acquisition of the alveolar structure of the lungs and the appearance of the diaphragm led to increased gas exchange. Diaphragm- This is a muscular partition that completely divides the body into two parts - chest and abdominal. The diaphragm is involved in the act of inhalation and exhalation. thermoregulation is achieved by the appearance of hair and skin glands

Due to the perfection of the digestive, respiratory and circulatory systems, the entire metabolism of mammals proceeds very intensively, which, along with a high body temperature, makes them less dependent on climatic conditions environment than amphibians and reptiles. The rapid progressive development of animals is also due to the fact that the highest of them developed live birth. The nutrition of the embryo in the womb is carried out through a special organ - placenta. After birth, the baby is suckled with milk. It is secreted by special mammary glands. All this greatly increases the survival rate of offspring.

Thanks to the height of organization and the perfect psyche, by the beginning of the Cenozoic era (65 million years ago), mammals were able to displace the reptiles that had dominated the Earth until then and occupy all the main habitats.

FEATURES OF THE STRUCTURE OF MAMMALS

External structure

Animals have well expressed: head, neck, torso and tail. On the head usually distinguish between the cranial region, located behind the eyes, and the facial, or muzzle, located in front. Eyes equipped with upper, lower and third eyelids. Unlike birds, the nictitating membrane (third eyelid) covers only half of the mammalian eye. On the sides of the head are large ears, at the end of the muzzle are paired nostrils. Mouth bordered by fleshy lips characteristic of mammals. On upper lip very hard hairs usually sit - vibrissae. Several of them are located above the eyes. They play the role of additional organs of touch. Under the root of the tail is the anus, and a little anterior to it is the urogenital. In females, 4–5 pairs of nipples are located on the sides of the body on the ventral side. The limbs are five- or four-fingered, the fingers are armed with claws.

Skin

Wool, covering the body of mammals, is a derivative of the skin. There are two types of hair - guard and soft - downy. The skin is made up of two main layers - epidermis And corium. The first is a thin stratum corneum, and the second is very thick, dense. Bottom part it forms subcutaneous tissue.

Skeleton

The spine consists of five sections: cervical, thoracic, lumbar, sacral and caudal. The vertebrae have flat articular surfaces characteristic of mammals and are separated from each other by round cartilaginous discs - menisci.

The cervical region in all mammals (with very rare exceptions) contains 7 vertebrae. (Both the mouse and the giraffe have 7 cervical vertebrae). These vertebrae lack free ribs. The thoracic region contains 12-13 vertebrae, all of which are equipped with ribs. The anterior seven pairs of ribs are connected to the sternum and are called "true ribs". The next five pairs do not reach the sternum. The lumbar ribs are devoid of and usually contain 6-7 vertebrae. The sacral region is formed in most mammals by four fused vertebrae. The anterior ones usually bear two processes, with the help of which the pelvis is attached. The caudal region is very variable in the number of vertebrae.

Scull It is divided into axial, consisting of the bones surrounding the brain, and visceral (facial), which includes the bones surrounding the mouth opening - the sky, the bones of the upper and lower jaws.

Shoulder girdle represented only by the scapula and clavicle, and there is no crow bone (coracoid) in mammals. In fast runners, the clavicle (ungulates) usually also disappears. The pelvic region consists of a pair of innominate bones, each formed by the fusion of the ilium, ischium, and pubis. The skeleton of paired limbs has three typical sections. In the forelimbs, this is the shoulder, forearm and hand, and in the hind limbs, the thigh, lower leg and foot. In mammals, on the hind limbs, a rounded tendon bone appears in the knee joint - the patella.

Muscular system

This system in animals reaches exceptional development and complexity. They have several hundred separate striated muscles. A feature of the muscular system of mammals is the presence of a diaphragm and the appearance of subcutaneous muscles. Diaphragm- This is a domed muscular septum that separates the thoracic region from the abdominal region. In the center it is perforated by the esophagus. The diaphragm takes part in the acts of respiration and excrement of animals. The subcutaneous musculature is a continuous subcutaneous layer. With its help, animals can move parts of the skin. The same muscles take part in the formation of the lips and cheeks. In monkeys, it has almost disappeared and is preserved only on the face. There she received an unusually strong development - this is the so-called mimic muscles.

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Nervous system

Brain The animal has powerfully developed hemispheres of the forebrain and cerebellum. They cover all other parts of the brain from above.

forebrain consists of the cerebral hemispheres, covered with a gray medulla - the cerebral cortex. The olfactory lobes extend forward from the hemispheres. Between the hemispheres is a wide jumper of white nerve fibers.

diencephalon has a funnel and optic chiasm, like other classes of vertebrates. The pituitary gland is attached to the funnel of the diencephalon, while the epiphysis is located above the cerebellum on a long stalk. midbrain differs in very small sizes, in addition to the longitudinal furrow, it also has a transverse one, which is characteristic only of mammals. Cerebellum consists of an unpaired part - the worm and two lateral parts, which are very large and are usually referred to as the cerebellar hemispheres. Medulla has a feature that is also characteristic only of mammals. On the sides of this brain, bundles of nerve fibers leading to the cerebellum are isolated. They are called the posterior cerebellar peduncles. The medulla oblongata passes into the spinal cord.

sense organs

They are highly developed in mammals, and, in accordance with the ecological specialization of a particular group, the leading role is either smell, or sight, or hearing, or even touch. The organs of hearing in animals are especially well developed. They have bony auditory drums and large mobile external ears.

Digestive organs

Oral cavity limited in animals by lips. Lips take part in grasping and holding prey. The oral cavity is bounded from above by a hard bony palate. Due to this, the choanae (internal nostrils) are pushed back towards the pharynx. This allows the animals to breathe while the food is in the mouth. The sides of the oral cavity are limited by soft muscular cheeks, and at the bottom of it there is a large muscular tongue. Its functions are to perceive taste sensations and push food during chewing under the teeth and into the throat during swallowing. ducts open into the mouth salivary glands(4 paired glands - parotid, infraorbital, submandibular and sublingual). Teeth do not grow to the surface of the bone, as in the previous classes, but sit in independent cells. The teeth are differentiated into incisors, canines and molars. The tooth itself consists of such parts as a crown with a working surface, the body of the tooth and its root. throat of beasts short, the windpipe and choanae open into it. Thus, in mammals, the pharynx is the crossroads of two pathways - food and respiratory. Esophagus is a simple, highly extensible muscular tube. After passing through the diaphragm, it connects to the stomach. Stomach has the appearance of a large horseshoe-shaped curved bag that lies across the body. A fat-filled peritoneum hangs from the stomach, which covers everything with an apron. internal organs. Liver located under the diaphragm, its flows open in duodenum, in the loop of which lies the pancreas. Most mammals have a gallbladder. Intestines can be of various lengths, it depends on the composition of the feed. In a herbivorous rabbit, the intestines are very long - 15-16 times longer than the body. Its divisions are the small, large and rectum. At the beginning of the large intestine in mammals there is an unpaired blind outgrowth - the caecum. The intestine opens to the outside with an independent anal opening.

Respiratory system

Larynx, as usual for mammals, has a cricoid cartilage, in front of which is a large thyroid cartilage. The larynx of a mammal is complex. On inside larynx stretched vocal cords. These are paired elastic folds of the mucous membrane, stretched in the cavity of the larynx and limiting the glottis. Lungs represent a pair of spongy bodies hanging freely into the chest cavity. Their internal structure is characterized by great complexity. The trachea near the lungs divides into two bronchi. The bronchi, entering the lungs, are divided into secondary bronchi, which, in turn, are divided into bronchi of the third and fourth order. They end in bronchioles. The ends of the bronchioles are swollen and braided with blood vessels. These are the so-called alveoli, where gas exchange takes place.

Circulatory system

Heart animals, like birds, has four chambers, and the left ventricle drives blood through the systemic circulation and, like birds, has much thicker walls than the right one. A large vessel departs from the left ventricle - the aorta, which begins the systemic circulation. Arterial blood is supplied to all organs of the body, and venous blood is collected through the vein system. The largest of them - the posterior and two anterior vena cava - flow into the right atrium. From the right atrium, blood enters the right ventricle, from here the pulmonary circulation begins, or, as it is also called, the pulmonary circulation. Venous blood is ejected from the right ventricle into the great pulmonary artery. This artery divides into right and left, leading to the lungs. From each lung, blood is collected in the pulmonary vein (the blood in it is arterial), both veins merge and flow into the left atrium. Further, from the left atrium, the blood flows into the left ventricle and again goes through the systemic circulation.

Organs, secretions

At mammals is a pair of bean-shaped kidneys located in the lumbar region. From the inner concave side of each kidney departs along the ureter (thin tube), which flows directly into the bladder. The bladder opens into the urethra.

Sex organs

In mammals, these are paired testes (in males) or paired ovaries (in females). The testicles have a characteristic oval shape. Adjacent to them are the appendages of the testicles. Paired vas deferens open at the beginning of the urethra. The end parts of the vas deferens are expanded into the seminal vesicles. The paired ovaries of the female have an oval-flattened shape. Near each ovary is an oviduct. At one end, the oviduct opens into the body cavity, and at the opposite end, without a visible border, it passes into the uterus. The uterus in animals is bicornuate, the right and left horns of the uterus open independently into the vagina. It is unpaired. At its posterior end, it gradually passes into the urethra and the bladder opens into it. Outwardly, the vagina opens with the urogenital opening.

Embryo development

egg cells develop in the ovary, then mature cells, upon exiting the ovary into the body cavity, are caught there by the funnel of the oviduct. Thanks to the flickering movements of the cilia of the tube (oviduct), the egg moves along it, and if the female is fertilized, then in the tube (usually in its first third) the egg merges with the sperm. The fertilized egg continues to slowly descend into the uterus and at the same time its crushing (dividing the egg into many cells) begins. Having reached the uterus, the egg, which by that time has turned into a dense multicellular ball, is introduced into the wall. There, nutrients begin to flow to it. Pretty soon, a placenta forms around the implanted embryo. This is the shell of the fruit, very characteristic of mammals. The placenta is a spongy organ rich in blood vessels, in which children and maternal parts are distinguished. The nursery consists of the villi of the germinal membrane, and the maternal one consists of the wall of the uterus. During childbirth, the muscular layer of the uterus is greatly reduced and the baby placenta (chorion), by that time associated very slightly with the mucous membrane of the uterus, opens and exits along with the newborn in the form of a child's place.

FEATURES OF THE BEHAVIOR OF MAMMALS

Intraspecific behavior in mammals is characterized by aggression. It is due to the protection of the species from external and intraspecific factors. Aggressive behavior often manifests itself already in the early stages of ontogeny, which can lead to the destruction of the youngest cub (cainism), and sometimes to eating it by its brethren (cannibalism). On the ground aggressive behavior infanticide (infanticide) is also possible in predatory mammals(lions), rodents (ground squirrels), etc. When protecting a group territory, collective aggressive behavior of the owners towards strangers is observed. In many cases, aggressive behavior is stimulated by sex hormones. Under the influence of aggressive influence, the body experiences a state of tension, stress (English stress - tension). With moderate stress, an increase in the activity of the autonomic nervous system is found. Stimulation of the adrenal medulla through the autonomic nerves causes them to release adrenaline into the blood. At the same time, there are changes in various parts organism. The secretion of sweat glands begins, the hair stands on end, the heart beats faster, breathing becomes more frequent and deep, blood from digestive tract redirected to the muscles. All this prepares the body for energetic actions of the required type. Under the influence of chronic stress, the animal becomes ill and may die.

Forms of aggression are diverse, let's try to classify them.

3.1 Interspecies aggression

1. Aggressiveness of a predator in relation to the prey

In nature, some species inevitably attack others. The mutual influence of predator and prey leads to evolutionary competition, forcing one of them to adapt to the development of the other. But, it is worth noting that the predator never completely destroys the prey population, some balance is always established between them. Strictly speaking, ethologists generally do not consider the behavior of a predator to be aggressive (Lorenz, Dolnik, and others), or they consider it a special form of aggression, different from all others. “When a wolf catches a hare, this is not aggression, but hunting. Similarly, when a hunter shoots ducks or a fisherman catches fish, this is not aggressive behavior. After all, they all feel neither hostility, nor fear, nor anger, nor hatred towards the victim. AK. Lorentz writes: “The internal origins of the behavior of the hunter and the fighter are completely different. When a lion kills a buffalo, that buffalo causes no more aggressiveness in him than in me a delicious turkey hanging in the pantry, which I look at with the same pleasure. The difference in internal motives is clearly visible already from the expressive movements. If a dog chases a hare, then it has exactly the same tense - joyful expression with which it greets the owner or anticipates something pleasant. And from the lion's muzzle, at the dramatic moment of the jump, one can quite clearly see, as it is recorded in many excellent photographs, that he is not at all angry. Growls, flattened ears and other expressive movements associated with fighting behavior can be seen in hunting predators only when they are seriously afraid of their armed prey, but even then only as a hint.

A wonderful illustration of all that has been said is an excerpt from the story of J. London "White Fang", where the wolf cub, which has just dealt with partridge chicks, enters into a fight with the mother partridge. “... He was met by a winged whirlwind. The swift onslaught and furious beats of the wings blinded, stunned the wolf cub. He buried his head in his paws and squealed. Blows rained down from new force. The partridge mother was beside herself with rage. Then the wolf got angry. He jumped up with a growl and began to fight back with his paws, then he sunk his small teeth into the bird's wing and began pulling and dragging it from side to side with all his strength. The partridge thrashed, hitting him with its other wing. It was the wolf cub's first fight. He rejoiced. He forgot all his fear of the unknown and was no longer afraid of anything. He tore and beat Living being that hit him. In addition, this living being was meat. The cub was lusting for blood. He was too engrossed in the fight and too happy to feel his own happiness…”

Continuation
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2. a) Much closer to genuine aggression than the hunter's attack on the prey, the reverse case of the prey's counterattack against the predator. An attack on a predator-devourer makes obvious sense for the conservation of the species. Even when the attacker is small, he causes very sensitive troubles to the object of attack. This is especially true for herd animals, which attack a predator in a crowd (the so-called mobing). There are many examples. Ungulates often form a dense ring, putting their horns forward and protecting the cubs. Musk oxen repulse the attacks of wolves in this way, buffaloes defend themselves from lions. In our domestic cows and pigs, the instinct of a general attack on a wolf is firmly in the blood.

2. b) As in the attack of a predator on prey or in the persecution of a predator by its victims, the species-preserving function of the third type of combat behavior, which Lorentz called the critical reaction, is also obvious. The expression "fight like a cornered rat" symbolizes a desperate struggle in which the fighter puts everything, because he can neither leave nor count on mercy. This form of fighting behavior, the most violent, is motivated by fear (aggression and fear are twins), a strong desire to escape, which cannot be realized because the danger is too close. The animal, one might say, no longer risks turning its back on her - and attacks itself, with "the courage of despair." This is exactly what happens when escape is not possible due to limited space - as in the case of a cornered rat - but the need to protect a brood or family can also work in the same way. An attack by a mother female on any object that gets too close to the cubs should also be considered a critical reaction. With the sudden appearance of a dangerous enemy within a certain critical zone, many animals violently attack him, although they would run from a much greater distance if they noticed his approach from afar.

In addition to these special occasions interspecific struggle, there are others, less specific. Any two animals of different species, approximately equal in strength, can grapple for food, shelter, etc. In all of the above cases of struggle between animals, there are common feature: here it is quite clear what benefit each of the participants in the battle receives for the preservation of the species. But intraspecific aggression (aggression in the narrow and unique sense of the word) also serves to preserve the species, although this is not so obvious.

3.2 Intraspecific aggression

1. Territorial aggression(aggression aimed at protecting the territory)

Active protection- an essential sign of territorial behavior. Aggressiveness is manifested in relation to any representative of the same species, especially the same sex. It reaches its maximum at the beginning of the breeding season, when territories are just being established. The territory should not be imagined as a clearly defined space with well-defined boundaries (it can be temporary). As a rule, this zone is determined only by the fact that the readiness of a given animal to fight is highest in the place most familiar to him, namely, in the center of his area. That is, the threshold of aggressiveness is lowest where the animal feels most confident, where its aggression is least suppressed by the desire to escape. With distance from this "headquarters" combat readiness decreases as the situation becomes more alien and fearsome. With approaching the center of the habitat, aggressiveness increases in geometric progression. This increase is so great that it compensates for all the differences in size and strength that may occur in adult sexually mature individuals of the same species.

When the vanquished takes flight, one can observe a phenomenon that occurs in all self-regulating systems with inhibition, namely, oscillations. The pursued - as he approaches his headquarters - regains courage, and the pursuer, having penetrated into enemy territory, loses courage. As a result, the fugitive suddenly turns around and - just as suddenly, how vigorously - attacks the recent winner, whom he now beats and drives away. All this is repeated several more times, and, in the end, the fighters stop at a well-defined point of balance, where they only threaten each other.

This simple mechanism of struggle for territory ideally solves the problem of a “fair”, that is, the most beneficial for the whole species in its totality, distribution of individuals over an area in which this species can live. At the same time, even the weaker ones can feed themselves and give offspring, albeit in a more modest space.

Animals can achieve the same effect without aggressive behavior, simply by avoiding each other. An important role here is played by "marking the area", especially on the periphery of the site. Excrements, secretions of skin glands, optical signs - bark torn from tree trunks, trampled grass, etc. Mammals for the most part "think with their nose", so it is not surprising that marking their possessions with smell plays an important role in them. Many mammals leave scent signals where they encounter or expect to encounter a rival. Dogs urinate for this purpose, hyenas, martens, chamois, antelopes and other species use special glands, the secrets of which mark the soil, shrubs, stumps, stones, etc. Brown bear scratching his back against a tree while urinating. Although behind such labels there is already a silent threat of aggression.

Fight for territory- a very important function of males. Without good land, a family or herd cannot exist; the prosperity of the group depends on their quantity and quality. You need to try to expand the possessions all the time, including at the expense of neighboring groups. Therefore, skirmishes over territories are inevitable. Human ancestors also lived in territorial groups, and for them the struggle for territory was inevitable. Territorial wars among some tribes became the main occupation in life.

So, taking into account the foregoing, it can be considered reliable that the uniform distribution of animals of the same species in space is the most important function of intraspecific aggression. In addition, Manning highlights another aspect of territorial behavior. Interestingly, in territorial animals, the first reaction of the male to the female contains elements of attack and flight. Such aggressiveness is very important in the formation of "couple attachment". This aggression, although it may occur between a male and a female, is largely redirected outwards to neighboring animals. Often the male attacks the male, and the female attacks the female. The cooperation of the male and female in the defense of the territory strengthens the bond between them.

2. Mating tournaments

Mating battles are always engaged in a certain category of individuals. In most cases, males fight, attacking exclusively or mainly other males of their own species. Sometimes both male and female fight, and when this happens, the male attacks the other male, and the female attacks the other female. Different types fight differently. First of all, unequally used weapons. Dogs bite each other, horses and many other ungulates try to kick the opponent with their front limbs. Deer are measured by strength, grappling with antlers. What are these collisions for? Charles Darwin had already noticed that sexual selection - the choice of the best, most powerful animals for procreation - is largely determined by the struggle of rival animals, especially males. The strength of the father provides immediate advantages to the offspring in those species where the father takes an active part in the care of children, especially in their protection. The close connection between the care of males for offspring and their fights is most clearly manifested in those animals that are not territorial in the sense of the word described above, but lead a more or less nomadic lifestyle, such as large ungulates, terrestrial monkeys, etc. In these animals, intraspecific aggression does not play a significant role in the distribution of space; in the dispersal of such species as bison, various antelopes, horses, which gather in huge communities and to which the division of plots and the struggle for territory are completely alien, because they have plenty of food. However, the males of these animals fight fiercely and dramatically with each other, and the selection resulting from this fight leads to the emergence of large and well-armed family protectors. Thus, such imposing fighters as buffalo bulls or male large baboons.

In this regard, it is necessary to mention one more fact - purely intraspecific selection can lead to the appearance of traits that are not only useless in terms of adaptation to the environment, but also directly harmful to the preservation of the species. Deer antlers, for example, have developed exclusively for fights, these antlers are not suitable for anything else. Deer protect themselves from predators only with their front hooves. Similar signs develop in those cases when selection is directed only by the competition of relatives, without connection with the extraspecific environment. Returning to the theme of the significance of the duel for the preservation of the species, we can say that it serves as a useful selection only where fighters are tested not only by intraspecific dueling rules, but also by fights with an external enemy. The most important function of the duel is the choice of the combat defender of the family, thus, another function of intraspecific aggression is to protect offspring. The proof can be the fact that in many animals in which only one sex takes care of the offspring, representatives of this particular sex are truly aggressive towards their relatives, or their aggressiveness is incomparably stronger. Something similar is observed in humans.

Aggression in the community of social animals, leading to the establishment of a hierarchy

Hierarchy- this is the principle of organization, without which, obviously, an ordered living together higher animals. It consists in the fact that each of the individuals living together knows who is stronger than himself and who is weaker. A dominance-subordination relationship is established in the group, and the number and severity of clashes is reduced, because each can retreat without a fight before the stronger one - and can expect the weaker one to retreat before him in turn if they get in each other's way. Dolnik emphasizes that the victory in skirmishes does not necessarily go to the one who is stronger. It is given to those who are more aggressive: they like to impose conflicts, they threaten a lot and skillfully, and they themselves relatively easily withstand other people's threats. So, the individual that wins most often becomes the dominant. Inevitably, there comes a moment when the dominant takes out his anger on the subdominant (due to a spontaneous outburst of aggression). He will not answer him, but will redirect aggression to the one who is lower on the hierarchical ladder (after all, it is scary to touch the dominant). By being redirected, aggression will reach those who are at the lowest level. There is no one to take out aggression on anyone, and it often accumulates. In a large group “on top” there is always a dominant, but there may already be two or three subdominants. This is how a hierarchical pyramid is formed, the lower layer of which consists of individuals who give in to everyone. They have accumulated a large unrealized aggressiveness, hidden by ingratiating behavior in front of their superiors. This is the law of nature and it is impossible to resist it.

Dog-headed monkeys - baboons, hamadryas and others - form hierarchical pyramids according to age. At the head of the group are several older males who have the greatest power and responsible for the safety of the group (gerontocracy). But, younger males can form alliances and attack superior individuals. Although these alliances are not strong, because the monkeys betray each other all the time, especially when it comes to a fight. Thus, unions can change the hierarchical pyramid by "revolution from below". The formation of a pyramid according to age is also characteristic of a person. In traditional societies, the age hierarchy is observed very strictly. But the formation of unions of subordinates in order to overthrow the dominants is also a common thing, known from antiquity to the present day.

The wide distribution of the hierarchy strongly indicates its important species-preserving function: thus, unnecessary struggle between members of the community is avoided. Here the question arises: how is this better than a direct ban on aggression against members of the community? Ethologists argue that it is impossible to avoid aggression. Firstly, often to the community ( wolf pack or a herd of monkeys) aggressiveness towards other communities of the same species is urgently needed, so that fighting should be excluded only within the group. Secondly, the tensions that arise within a community as a result of aggressive urges and the hierarchy that grows out of them can give it much useful structure and strength. The farther apart the ranks of two animals, the less hostility between them. And since the superior individuals (especially males) necessarily intervene in the conflicts of the inferior ones, the principle “The place of the strong is on the side of the weak!” works.

Age hierarchy did not come about by chance either. With the general progress of evolution, the role of the experience of old animals increases more and more; one might even say that the joint social life in the most intelligent mammals, it acquires, due to this, a new function in the preservation of the species, namely, the traditional transmission of individually acquired information. Naturally, the converse is also true: social life together produces selection pressure towards better development of learning abilities, since these abilities in social animals benefit not only the individual, but also the community as a whole. Thereby and long life, significantly exceeding the period of sexual activity, acquires value for the conservation of the species.

Continuation
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CONCLUSION

In the first chapter of the abstract, I examined the main features of the progressive evolution of mammals that helped them become the dominant animals on the planet. These are three main groups of adaptations: those associated with a constant high body temperature; associated with the peculiarities of reproduction and education of cubs; Related big brain in animals of this group. The structure and physiology of animals are also considered, and their modern taxonomy.

In the second chapter, I considered the behavioral features of mammals, in particular, interspecific and specific aggression. It has been proven that life without aggression is impossible, even if you create an ideal environment that does not contain any irritants. With a long non-fulfillment of any instinctive action (manifestation of aggression), the threshold of irritation decreases. Reducing the threshold of irritation can lead to the fact that under special conditions its value can drop to zero, that is, the corresponding instinctive action can “break through” without any external stimulus. In principle, every truly instinctive action, which is deprived of the opportunity to discharge, puts the animal in a state of general restlessness and forces it to search for a discharge stimulus. And the lowering of the irritating threshold and search behavior, rarely in any cases, are manifested as clearly as in the case of aggression.

The benefits of aggression can be considered proven. The living space is distributed among the animals in such a way that, if possible, everyone finds food for himself. For the benefit of the offspring, the best fathers are selected and best mothers. Children are protected. The community is organized in such a way that a few wise males have sufficient authority so that the decisions needed by the community are not only made, but also carried out. The goal of aggression is never to destroy a kinsman, although, of course, an accident can occur during the duel when the horn hits the eye or the canine in the carotid artery. Aggression is not at all a destructive principle - it is only a part of the organization of all living beings, preserving their system of functioning and their very life. Like everything in the world, she can make a mistake - and in doing so, destroy life. However, in the great accomplishments of the formation of the organic world, this force is destined for good.

REFERENCES

1 .Levitin M.G. Biology: Botany. Zoology. Anatomy and physiology of man. [Text] / M.G. Levitin, T.P. Levitin. - St. Petersburg: Parity, 2000;

2 .Lecture in zoology. Features of animals;

3. Dolnik V. Naughty child of the biosphere [Text] / V. Dolnik. - M.: "Pedagogy - press", 1994;

4.Lorenz K. Aggression: the so-called "evil" [Text] / K. Lorenz. - M.: "Progress", 1994;

5. Manning O. Animal behavior [Text]/O. Manning. - M.: "Mir", 1982;

6. Dewsbury, D. Animal Behavior: Comparative Aspects [Text]/D. Dewsbury. - M.: "Mir", 1981;

7.Fabry, K. Fundamentals of zoopsychology [Text] / K. Fabry. - M.: MGU, 1976;

8. Tinbergen N. Social behavior of animals [Text] / N. Tinbergen.- M.: "Mir", 1993;

9. Bram A. Animal life: Mammals [Text] / A. Brem. - M.: "Terra", 1992;

10. Tanner ABOUT. Methods of protection in animals [Text] / O. Tenner. - M.: "Mir", 1985;

11. Biological encyclopedic dictionary [Text] / M .: “ Soviet Encyclopedia", 1989;

12. London J. White Fang [Text] / J. London. - Yekaterinburg: "Northern House", 1992.

Mammals are the most highly organized vertebrates. They differ in a wide variety of sizes and external structure, which depends on the conditions and lifestyle. For example, a baby shrew has an average weight of 1.5 g, African elephant- 4-5 tons, and blue whale up to 150 tons.

FEATURES OF THE EXTERNAL STRUCTURE

Consider them on the example of a dog. The body of mammals is divided into head, neck, trunk, tail and

two pairs of limbs. The head is elongated. It distinguishes the cranial and facial department or muzzle. On the head is a mouth bordered by movable fleshy lips, above which is a nose with a pair of nostrils. On the sides of the head are a pair of eyes protected by movable eyelids. The third eyelid (nictitating membrane) is reduced. Behind the eyes is a pair of movable auricles, characteristic only of mammals. The neck provides a movable connection of the head with an elongated torso, highly elevated on the fore and hind limbs above the ground. On the ventral side of it (in females) there are several pairs of mammary glands, and under the root of the tail there is an anus. The limbs are five-fingered. All fingers end in claws.

BODY COVERS

The skin of mammals consists of two layers - epithelial and skin proper. The epithelium is keratinized. Due to it, sebaceous and sweat glands, hair, claws, nails, horns, hooves are formed. The presence of hair feature mammals. The hair evenly covers the dog's body and is divided into awns (long and coarse), undercoat (short and thin) and downy hair. The awn protects the skin from damage, and the undercoat serves for thermal insulation. Hair is made up of a horny substance called keratin. In dogs, due to the seasons, they change 2 times a year.

The sebaceous glands located in the skin produce a secret that lubricates the surface of the skin and hair, helping to maintain its elasticity, and also protects against the penetration of microorganisms.

There are few sweat glands in dogs, tk. thermoregulation in them is carried out due to the evaporation of water from the surface of the tongue. The mammary glands are also derivatives of the epidermis, the secret of which the young feed on. In some mammals, sweat or sebaceous glands are modified into odorous ones: musky (muskrat, beaver), anal (predators). Their secret serves for species identification, protection, and marking of the occupied territory.

SKELETON AND MUSCLE

The skeleton has a structure typical of terrestrial vertebrates, but at the same time a number of features.

The skull is formed by several paired and unpaired fused bones. Its brain section has larger volumes than that of reptiles, which is determined by the significant development of the brain, especially the cortex. The development of the secondary jaw and the bony hard palate is characteristic of the facial section.

The spinal column consists of 5 sections: cervical, thoracic, lumbar, sacral and caudal. The cervical region consists of 7 vertebrae, which is typical for almost all mammals. The number of thoracic vertebrae ranges from 12 to 15. Ribs are attached to them, which fuse with the sternum to form the chest. Massive lumbar vertebrae (6) are movably connected. The sacral vertebrae (3-4) fuse motionlessly between themselves and the pelvic bones, creating support for the hind limbs. The caudal region is characterized by great variability in the number of vertebrae.

The girdle of the forelimbs of the dog is formed by paired shoulder blades and crow bones fused with them. Clavicles are absent. The shoulder girdle is connected to the axial skeleton through muscles and ligaments.

The girdle of the hind limbs is formed by paired innominate bones. They are formed as a result of the fusion of the iliac, pubic and ischial bones. Fusing with the sacrum, they form a closed pelvis.

The free limbs are five-fingered, have a structure typical of terrestrial vertebrates. The hind limb is characterized by the development of a tendon bone-calyx.

The muscles of mammals are highly specialized. The masticatory muscles, which are involved in the capture and grinding of food, achieve significant development and differentiation. A characteristic feature of the muscular system is the development of the subcutaneous muscles and the diaphragm. The appearance of the diaphragm improves ventilation of the lungs, and also divides the body cavity into chest and abdominal. The subcutaneous musculature plays a role not only in thermoregulation, but also in the transmission of information. Good development of the muscles of the limbs provides a high speed of movement.

INTERIOR STRUCTURE

The digestive system is characterized by the development of specialized teeth, a clear division of the intestinal tube into sections and its considerable length, which ensures efficient digestion and absorption of nutrients.

The oral cavity begins with the vestibule of the mouth, the outer wall of which is fleshy lips, and the inner wall is well-developed jaws, equipped with specialized teeth.

Dogs have 42 teeth, divided into incisors (12), canines (4), anterior (16) and posterior (10). The teeth have a root, which is fixed in the hole of the jaw, and a crown, the shape of which depends

on the type of teeth. Dogs have small, chisel-shaped incisors. The fangs are large, conical, used to capture and kill prey. Indigenous have wide tuberous crowns with a sharp cutting edge. The last premolar of the upper jaw and the first of the molar lower jaw form carnassial teeth. In the process individual development there is a change of milk teeth (incisors, canines and premolars) to permanent ones.

At the bottom of the mouth lies a muscular tongue, the surface of which is covered with taste buds. It is involved in mixing and swallowing food, as well as taste reception. The ducts of three pairs of salivary glands open into the oral cavity, the secret of which moisturizes food, and also contains enzymes that break down starch.

From the oral cavity through the pharynx and esophagus, food enters a well-developed simple stomach, and from it, after partial digestion, into the small intestine. The ducts of the liver and pancreas flow into its initial section, the duodenum. In the small intestine, food is hydrolyzed and absorbed. Undigested food remains in the large intestine, which is divided into the caecum and colon. In these sections of the intestine, the formation of feces occurs, which are removed outward through the rectum.

RESPIRATORY SYSTEM

Mammals breathe atmospheric air. The main role in gas exchange belongs to the lungs, which are associated with external environment respiratory tract. The respiratory tract includes the nasal cavity, nasopharynx, pharynx, larynx, trachea and bronchi, which form numerous branches in the lungs. The smallest bronchi - bronchioles - end in pulmonary vesicles - alveoli. In the latter, gas exchange takes place. In the development of the respiratory organs of mammals, the appearance of the epiglottal cartilage, the larynx, and the alveolar structure of the lung should be noted.

CIRCULATORY SYSTEM

Mammals have a four-chambered heart, consisting of two atria and two ventricles. From the left ventricle, unlike birds, the left aortic arch departs. Blood moves through two circles of blood circulation. The systemic circulation starts from the left ventricle. The arterial blood contained in it is delivered to the tissues through the system of vessels that depart from the aorta. Venous blood is collected in the anterior and posterior vena cava, which empty into the right atrium, where the large circle ends.

The pulmonary circulation begins in the right ventricle. From it, venous blood flows through the pulmonary artery to the lungs. Oxygenated arterial blood flows from the lungs to the left atrium through the four pulmonary veins.

In mammals, due to the development of a four-chambered heart, arterial and venous blood do not mix. The supply of tissues with oxygenated arterial blood enhances the course of redox processes in cells, increasing the level of energy metabolism. As a result, most modern mammals are able to maintain a constant body temperature and remain active in conditions of sharp changes in environmental temperatures.

ORGANIZATIONS

In the water-salt metabolism in mammals, the main role belongs to the secondary kidneys. They are paired compact bean-shaped bodies located on the sides of the lumbar spine. A pair of ureters depart from the kidneys, opening into the bladder, from which urine is excreted through the urethra. The kidneys secrete urine that is hypertonic in relation to blood plasma, which saves water by removing metabolic products and salts from the body.

NERVOUS SYSTEM

It consists of the brain, spinal cord and peripheral nerves extending from them. The dog brain is divided into 5 sections, like all vertebrates, but has a number of features compared to other classes of vertebrates. The greatest size and development reach the hemisphere of the forebrain. The bulk of them is the bark, on the surface of which there are a large number of convolutions. The hemispheres are connected to each other by the corpus callosum.

The midbrain is divided by furrows into quadrigemina, unlike other vertebrates that have colliculus. Through the anterior colliculus, the pathways of the visual tract go to the cortex, and through the posterior colliculus, the auditory tract. The cerebellum is large. It consists of hemispheres and a worm located between them. It ensures the maintenance of muscle tone, balance, coordination of movements. 12 pairs of cranial nerves leave the brain.

SENSORS

Well developed. The organs of vision are represented by a pair of eyes. The cornea of the eye is convex, the lens accommodates only due to a change in curvature. In connection with the development of the cortex, secondary associative visual centers are formed in it, located in its occipital lobe.

HEARING organ

Has a complex structure. In the process of evolution, three of its departments were formed: the inner, outer and middle ear. The outer ear is represented by a movable auricle and external auditory canal. Three auditory ossicles develop in the middle ear: the malleus, anvil, and stirrup. In the inner ear, the cochlea, in which the organ of Corti is located, reaches significant development.

Dogs, like many mammals, have a well-developed sense of smell. They are located in the upper-posterior part of the nasal cavity and represent a system of complexly branched shells, the surface of which is covered with olfactory epithelium. The sense of smell allows you to perceive various odors or combinations of them, characteristic of a group of individuals or an individual.

The organs of taste are represented by taste buds located on the tongue.

SKIN SENSITIVITY is represented by receptors that perceive temperature, pressure, touch.

REGENERAL SYSTEM

Dogs, like all mammals, are dioecious animals. Males have paired testes in which spermatozoa develop. The vas deferens from the testicles enter the urinary tract. Paired ovaries of females lie in the body cavity. The oviducts at one end face the body cavity, and at the other they open into the muscular organ inherent in higher mammals - the uterus, which opens outward with the vagina.

DEVELOPMENT

Fertilization is internal, occurring in the oviducts. Fertilized eggs, moving through the oviducts, begin crushing, turning into a multicellular embryo. When the embryo enters the uterine cavity, it attaches to its mucous membrane. At the site of contact of the embryo with the uterine mucosa, a child's place develops - the placenta. Through it, during embryonic development, the fetus receives nutrients and oxygen from the mother's blood, and at the same time removes metabolic products.

Dogs give birth to several blind, helpless cubs. Therefore, parents take care of their offspring. Mothers feed their cubs with milk, keep them warm, and protect them from enemies. And after the completion of feeding, the mother and father continue to protect the cubs, educate them, passing on individual experience to the offspring.

MAMMALIAN BEHAVIOR

The high level of development of the nervous system and sensory organs determine the complexity of mammalian behavior and its plasticity. It is based not only on a set of simple unconditioned reflexes that determine instinctive, innate behavior, but also on the ability to form conditioned reflexes and accumulate individual experience on their basis. In the process of interaction of the organism with the environment, there is a constant adaptation of its functional systems to changing conditions based on the formation of new temporary connections in the cerebral cortex and the extinction of old ones. Therefore, the nervous activity of mammals is characterized by mobility, richness and complexity of connections with the environment. Mammals are able to anticipate the course of many recurring events and, in certain situations, make appropriate decisions.

ORIGIN OF MAMMALS

Mammals come from a group of ancient primitive reptiles - animal-toothed lizards. According to the remains of the skeletons of animal-toothed lizards, it was established that they lived 200-230 million years ago. Their legs were located under the body and raised it high above the ground. Their teeth had roots and were divided into incisors, canines and molars, and the hard palate was bony, secondary. The skin integuments retained the features of the organization of the skin of amphibians.

Mammals appeared on earth in the Triassic period of the Mesozoic era. Their origin from reptiles is evidenced by signs common to both classes: the presence of a keratinizing epithelium with homologues of horny scales - hair, the presence of claws on the fingers, the homology of the limbs and their belts, the division of the spinal column into 5 sections, the similarity of the early stages of development of embryos. However, mammals have a four-chambered heart and are warm-blooded. They are characterized by feeding the cubs with milk, live birth.

The origin of mammals from reptiles is also evidenced by the fact that representatives of the subclass of primitive animals (platypus, echidna) occupy an intermediate position between reptiles and mammals in structure and reproduction characteristics.

Modern taxonomy divides mammals into 2 subclasses:

1. First beasts and 2. Real beasts. One detachment belongs to the first subclass - Single-pass. To the second subclass belong - infraclass - lower beasts with the order Marsupials and infraclass - Higher animals, uniting 19 modern and 12-14 extinct orders.

Both subclasses of mammals originate in the Triassic from the same original group of animal-like reptiles. In subsequent evolution, various adaptations of mammals contributed to their conquest not only of vast expanses of land, but also of air, soil, fresh and sea waters.

External structure

The animals have well-defined head, neck, torso and tail. On the head, a cranial region is usually distinguished, located behind the eyes, and a facial, or muzzle, located in front. The eyes are equipped with upper, lower and third eyelids. Unlike birds, the nictitating membrane (third eyelid) covers only half of the mammalian eye. Large ears are located on the sides of the head, paired ears lie at the end of the muzzle. nostrils See www.studiosharp.ru professional knife sharpening machine.

The mouth is bordered by fleshy lips characteristic of mammals. Very coarse hairs usually sit on the upper lip - vibrissae.

Several of them are located above the eyes. They play the role of additional organs of touch. Under the root of the tail is the anus, and a little anterior to it is the urogenital. In females, 4–5 pairs of nipples are located on the sides of the body on the ventral side. The limbs are five- or four-fingered, the fingers are armed with claws.

Skin

The wool that covers the body of mammals is a derivative of the skin. There are two types of hair - guard and soft - downy. The skin consists of two main layers - the epidermis and the corium. The first is a thin stratum corneum, and the second is very thick, dense. The lower part of it forms the subcutaneous tissue.

Skeleton

The skull is divided into axial, consisting of the bones surrounding the brain, and visceral (facial), including the bones surrounding the mouth opening - the sky, the bones of the upper and lower jaws.

The shoulder girdle is represented only by the scapula and clavicle, and there is no crow bone (coracoid) in mammals. In fast runners, the clavicle (ungulates) usually also disappears. The pelvic region consists of a pair of innominate bones, each formed by the fusion of the ilium, ischium, and pubis. The skeleton of paired limbs has three typical sections. In the forelimbs, this is the shoulder, forearm and hand, and in the hind limbs, the thigh, lower leg and foot. In mammals, on the hind limbs, a rounded tendon bone appears in the knee joint - the patella.

Muscular system

This system in animals reaches exceptional development and complexity. They have several hundred separate striated muscles. A feature of the muscular system of mammals is the presence of a diaphragm and the appearance of subcutaneous muscles. The diaphragm is a domed muscular septum that separates the thoracic region from the abdominal region. In the center it is perforated by the esophagus. The diaphragm takes part in the acts of respiration and excrement of animals. The subcutaneous musculature is a continuous subcutaneous layer. With its help, animals can move parts of the skin. The same muscles take part in the formation of the lips and cheeks. In monkeys, it has almost disappeared and is preserved only on the face. There she received an unusually strong development - this is the so-called mimic muscles.

Nervous system

The animal's brain has powerfully developed hemispheres of the forebrain and cerebellum. They cover all other parts of the brain from above.

The forebrain consists of cerebral hemispheres covered with a gray medulla - the cerebral cortex. The olfactory lobes extend forward from the hemispheres. Between the hemispheres is a wide jumper of white nerve fibers.

The diencephalon has a funnel and optic chiasm, as in other classes of vertebrates. The pituitary gland is attached to the funnel of the diencephalon, while the epiphysis is located above the cerebellum on a long stalk. The midbrain is very small in size, in addition to the longitudinal groove, it also has a transverse one, which is characteristic only of mammals. The cerebellum consists of an unpaired part - the vermis and two lateral parts, which are very large and are usually referred to as the cerebellar hemispheres. The medulla oblongata has a feature that is also unique to mammals. On the sides of this brain, bundles of nerve fibers leading to the cerebellum are isolated. They are called the posterior cerebellar peduncles. The medulla oblongata passes into the spinal cord.

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External structure

Animals have well expressed: head, neck, torso and tail. On the head usually distinguish between the cranial region, located behind the eyes, and the facial, or muzzle, located in front. Eyes equipped with upper, lower and third eyelids. Unlike birds, the nictitating membrane (third eyelid) covers only half of the mammalian eye. On the sides of the head are large ears, at the end of the muzzle are paired nostrils. Mouth bordered by fleshy lips characteristic of mammals. Very hard hairs usually sit on the upper lip - vibrissae. Several of them are located above the eyes. They play the role of additional organs of touch. Under the root of the tail is the anal opening, and a little anterior to it - the urogenital. In females, 4-5 pairs of nipples are located on the sides of the body on the ventral side. The limbs are five- or four-fingered, the fingers are armed with claws.

Skin

Skeleton

Muscular system

Nervous system

Brain The animal has powerfully developed hemispheres of the forebrain and cerebellum. They cover all other parts of the brain from above.

sense organs

Digestive organs

Oral cavity limited in animals by lips. Lips take part in grasping and holding prey. The oral cavity is bounded from above by a hard bony palate. Due to this, the choanae (internal nostrils) are pushed back towards the pharynx. This allows the animals to breathe while the food is in the mouth. The sides of the oral cavity are limited by soft muscular cheeks, and at the bottom of it there is a large muscular tongue. Its functions are to perceive taste sensations and push food during chewing under the teeth and into the throat during swallowing. The ducts of the salivary glands open into the mouth (4 paired glands - parotid, infraorbital, submandibular and sublingual). Teeth do not grow to the surface of the bone, as in the previous classes, but sit in independent cells. The teeth are differentiated into incisors, canines and molars. The tooth itself consists of such parts as a crown with a working surface, the body of the tooth and its root. throat of beasts short, the windpipe and choanae open into it. Thus, in mammals, the pharynx is the crossroads of two pathways - food and respiratory. Esophagus is a simple, highly extensible muscular tube. After passing through the diaphragm, it connects to the stomach. Stomach has the appearance of a large horseshoe-shaped curved bag that lies across the body. A fat-filled peritoneum hangs from the stomach, which covers all the internal organs with an apron. Liver located under the diaphragm, its flows open into the duodenum, in the loop of which lies the pancreas. Most mammals have a gallbladder. Intestines can be of various lengths, it depends on the composition of the feed. In a herbivorous rabbit, the intestines are very long - 15-16 times longer than the body. Its divisions are the small, large and rectum. At the beginning of the large intestine, mammals have an unpaired blind outgrowth - the caecum. The intestine opens to the outside with an independent anal opening.

Respiratory system

Larynx, as usual for mammals, has a cricoid cartilage, in front of which is a large thyroid cartilage. The larynx of a mammal is complex. The vocal cords are stretched on the inside of the larynx. These are paired elastic folds of the mucous membrane, stretched in the cavity of the larynx and limiting the glottis. Lungs represent a pair of spongy bodies hanging freely into the chest cavity. Their internal structure is characterized by great complexity. The trachea near the lungs divides into two bronchi. The bronchi, entering the lungs, are divided into secondary bronchi, which, in turn, are divided into bronchi of the third and fourth order. They end in bronchioles. The ends of the bronchioles are swollen and braided with blood vessels. These are the so-called alveoli, where gas exchange takes place.

Circulatory system

Organs, secretions

Sex organs

Embryo development