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Juvenile period. Stages of postembryonic human development. Establishment of sexual behavior

Prenatal period (aka embryonic, or intrauterine) the development of the animal ends with childbirth. After the moment of birth begins postnatal (he is postnatal, or postembryonic) a period that ends with natural death as a result of the aging of the animal. In mammals, it includes the following phases: newborn, mixed feeding , juvenile, puberty, morpho-physiological maturity and aging.

Birth is a turning point where the whole process of behavioral development takes on a new direction. Naturally, at the level of postnatal development, completely new factors and patterns appear due to the interaction of the organism with the true external environment. Under these new conditions, the innate elements of behavior continue to mature and merge with postnatal, individual experience. Therefore, despite the fundamental differences in the conditions for the formation of these two types of behavior, there is not only no gap between these stages of ontogeny of behavior, but there is a direct continuity. This is where preadaptive the meaning of embryonic behavior.

Postnatal development of behavior differs in specific patterns and proceeds differently in different animals, since their young are born at different stages of maturity.

It should be noted that all terrestrial animals with the most highly developed psyche, such as monkeys, beasts of prey, corvids, parrots, are born immature. L. A. Orbeli drew attention to this circumstance in his time. He noted that since mature-born calves begin to be exposed to the environment in an almost completely formed state, they are relatively little susceptible to its harmful effects. But at the same time, the possibilities for further progressive development of behavior, from his point of view, are extremely limited: there are only separate additional superstructures of conditioned reflex activity.

The situation is completely different in immature-born animals, in which the development of even hereditarily fixed, congenital forms of behavior is carried far beyond the intrauterine period. According to L.A. Orbeli, these cubs, despite the fact that in the initial period of life they still cannot do without parental assistance, are nevertheless in a more advantageous position. The development of the nervous system in them is not completely finished, and they can substitute their still developing innate forms of behavior under the influence of environmental agents. As a result, these behaviors are largely modified based on the interweaving of innate and acquired components in accordance with specific environmental conditions. As L. A. Orbeli writes, these animals "are born with such a poorly formed nervous system that all further postnatal development is a continuous processing of hereditary forms and newly emerging conditioned forms of behavior."

Of great importance for the development of young animals, especially in immature-born animals, the parental taking care of offspring, those. actions of animals that provide or improve conditions for the survival and development of offspring.

Early postnatal period(he is neonatal, or neonatal period) the period is of exceptional importance for the life of an individual, since at this stage of development, the most important relationships of the organism with the environment are formed, connections with the vital components of this environment are established, and the foundations of the behavior of an adult animal are laid.

This period of development is characteristic of immature-born calves and chicks of chick birds, which are born blind, deaf and helpless. During the postnatal period, the most significant changes occur in the development of the calf. From a completely helpless embryo, he turns into an animal, more or less capable of independent existence. Newborn babies spend this period in the womb.

Some physiological features of newborns

In the first minutes after birth, the respiratory center is turned on, which, until the end of life, regulates the supply of oxygen to the body and the removal of carbon dioxide, with the first breath, the lungs expand. Intensely licking a newborn the female helps the cub to take the first breath and helps to restore the tone of the blood vessels.

During the first weeks, the cubs unable to maintain a constant body temperature. The mother provides the required body temperature of the cubs, warming them with her body. When leaving the nest, the female covers the cubs with nesting material or closes the entrance to the burrow. In the absence of the female, the cubs crawl into a compact pile, which helps them to keep warm. This so called hilling reaction.

Parents of chicks keep chicks warm all the time. At the same time, they regularly replace each other, while one of them feeds himself and gets food for gluttonous chicks. In some species, only one parent warms the chicks, then the second provides food for him too.

A young mammal receives all the energy necessary for growth and development with breast milk. In accordance with this, its digestive system produces during this period only enzymes that are necessary for its digestion. At sucking With frequent short movements of the head, the baby pulls the nipple and rhythmically massages the mammary glands with its paws, which in combination contributes to the separation of milk.

Newborn cubs unable to urinate and defecate independently. Mother, exercising sphincter massage, licks the cubs and eats up all their secretions. In the absence of this behavioral characteristic, unsanitary conditions would quickly arise in the nest, and thus it is always clean and dry in it.

A similar adaptation exists in chick birds. The feces of chicks during the nesting period are enclosed in a dense mucous capsule, which the parents remove from the nest.

A similar situation is observed in all primates, including great apes. In humans, the absence of independent urination and defecation is not observed, but it is possible that common problems with constipation and "gas" in newborns are some atavism associated with our "zoological" past.

In young mammals during this period there is no daily rhythm characteristic of adults sleep and wakefulness associated with the alternation of day and night. In newborns, periods of sleep are regularly interspersed with periods of wakefulness, i.e. sucking. Some differentiation of the periods of day and night appears only towards the end of the period, when the cub's eyes are well erupted and he gradually begins to leave the dark den. And young calves fall asleep and sleep, not letting go of the mother's nipple. In the absence of the mother, the young often begin to suck on different parts of the body of their littermates. Obviously, this response contributes to the greater comfort of the newborn. The same can be observed in primates. An invention such as a pacifier, which has long been used to calm infants, has a completely physiological justification. Pacifiers are also used for artificial feeding of baby monkeys, and sometimes other babies.

Huge changes after birth occur in nervous system. Thus, the brain of a newborn puppy is no more than 12% of the weight of the brain of an adult dog. It grows intensively and by the end of the second month of the puppy reaches 3/4, and by the end of the sixth month - almost the full mass of the brain of an adult dog. The brain of a newborn baby is also different in its development. By the time of birth, those areas of the central nervous system are best developed that provide regulation of the functions necessary for its existence: digestion, breathing and sucking. The cerebral cortex of a newborn baby mammal already has well-developed basal gyri. However, nerve cells (neurons) in the first days after birth are still very immature.

For a long time, among psychologists, there was an opinion that the underdeveloped brain of newborns is the prerogative of humans, and animals are born with a practically matured brain, which allows them, immediately after birth, to implement an innate program of behavior that is allegedly absent in humans. This statement is fundamentally wrong, and newborn babies fully present all the innate reactions typical of all immature mammals.

Behavioral development of newborns

By the time of birth in cubs mammals the olfactory, gustatory, skin-temperature and vestibular analyzers function. The first behavioral response that a newborn displays is a positive response to a warm, hairy surface (Figure 13.1, a, b). This reaction persists throughout the neonatal period and contributes to the formation of a crowding reaction. In newborns, the manifestation of this reaction is that the child calms down when the mother takes him in her arms and presses him to her body.

The newly born baby, while still being connected by the umbilical cord to the placenta, already begins its way to the nipples and, having reached them, begins to suck (Fig. 13.1, c). This congenital food reaction in the first hours after birth, like a snowball, it is overgrown with conditioned reflex reactions. Gradually, the baby's movements are improved, he learns to find the milkiest nipples, recognizes the smell of the mother.

Rice. 13.1.

a - cubs of a marsupial possum; b - mice; v - puppies; G - baby chimpanzee

Primate babies are characterized by grasping reflex , manifested in reflexive squeezing of the hand (see Fig.13.1, G). It helps to keep the baby monkey on the mother's body. The same reflex is also noted in newborn babies. Moreover, its presence is a sign of the physiological maturity of a newborn baby.

The search for a nipple in primates is expressed in an instant turn of the head with an open mouth after touching a warm object to the cub's face. This reaction can also be observed in newborn babies.

Thus, the first period of a newborn baby's life is characterized primarily by rapid growth and improvement of unconditional reflex reactions. Towards the end, the cubs begin to walk, their eyes open. Behavior improves - games begin, defensive reactions arise. The duration of this period may be different: for example, in canine predators, it lasts 18–20 days, in small rodents, 8–10 days, and in large primates, 3-4 months.

During the neonatal period, tactile contacts are of particular importance. Cubs are constantly in contact with each other, the mother licks them and nudges them. Baby primates are constantly on the mother's body - first at the chest, and later on the back. Many nationalities raise children in the same way. Special experiments related to tactile deprivation have shown that pups raised in isolation with a minimum of tactile contacts lag behind in development, their eyes open later, and they later begin to move independently. Children who are deprived of direct contact with their mother after birth, placed in children's hospitals or baby homes, often develop the phenomenon of so-called hospitalism. It is expressed in the fact that children lag behind in physical development, they have weight loss, lethargy, lethargy, increased drowsiness, muscle hypotonia. There is also a noticeable lag in the emotional sphere: the lack of visual tracking, turns to the voice of an adult, they practically stop crying, constantly sucking their finger. In the future, these children noticeably lag behind in motor and mental development. In the most advanced cases, hospitalism can lead to severe mental impairment.

Birds. The behavior of chicks of chick birds develops in a similar way. The first reaction of the chick after hatching to any touch is stretching the neck and opening the mouth wide. This reaction is similar to the search for a nipple in mammals and during the first few days it manifests itself on almost any stimulus. As the auditory analyzer develops, the chicks begin to respond to a certain stimulus: a slight shaking of the edge of the nest at the moment of arrival of an adult bird, the touch of the bird's paws to the hole in the hollow, a specific acoustic "food signal" of the parent, etc. After the chicks open their eyes, they begin to respond to visual signals, for example, to the shading of the entrance hole by an arriving adult bird or to its silhouette at the edge of the nest. A stronger than usual shaking of the nest or an unusual sound induces a defensive hiding response in the chicks. The feeding behavior of chicks also becomes more complex: it becomes orderly. Arriving with food, an adult bird descends to a strictly defined point on the edge of the nest and lowers the food into the wide open mouth of the chick located in a strictly defined zone of the nest. After that, the bird takes the capsule with the feces of the chick, which it fed on the previous arrival, and flies away with it. As a result, all chicks are fed and cleaned. This is possible due to the constant cyclic movement chicks in the nest. After feeding, the chick moves in a certain direction, giving way to the next. At the same time, all chicks in the nest move in a circle. A full cycle of movement - from the zone with the maximum probability of receiving food through all subsequent ones again to this zone - takes on average 40-50 minutes. It is thanks to this cyclical activity that the hungry chick again receives food.

This idyllic picture is not observed in all species. In some birds, there is fierce competition between chicks, which leads to the partial death of the brood.

By the end of their stay in the nest, they are overgrown with feathers, and their sensory systems finally mature. Soon they leave the nest and turn into so-called fledglings, which parents continue to feed for some time.

Mixed feeding period

This period of ontogenesis (Fig.13.2) should be considered as transitional (sometimes they call it that). Its beginning marks the emergence of interest in food, consumed by adult animals. This interest arises when enzymes necessary for the digestion of adult food and teeth begin to erupt. At the same time, the cub appears chewing movements - Until now, sucking has been the only answer to any irritation in the mouth. In primate babies, grasping movements forelimbs: whatever they manage to grab, they taste. Similar behavior is observed in children from the moment when they form normal grasping movements of the hands. The child reflexively pulls any grasped object into his mouth. This reaction persists in children often up to 12-15 months.

During this time, some parents begin to bring solid food to the young. However, despite the developmental progress, the young continue to consume breast milk and be under the care of parents. Predators begin to teach their young to hunt behavior, bringing them half-dead prey. When the cubs, having killed the game, begin to eat it, the parents often punish the too greedy and aggressive offspring. Cubs of rodents begin to eat food in the nest, stored in advance by their parents.

Rice. 13.2.

the beginning of the game struggle

The transition from milk to mixed nutrition occurs at a time when the baby's olfactory, auditory and visual analyzers are already mature enough for the perception and differentiation of objects in the external world and the formation of numerous conditioned reflexes. First of all, the calf forms conditioned food reflexes, which provide a full-fledged act of nutrition while the cub is still in the nest.

As the movements improve, the cub begins to separate from the mother and brothers, to leave the nest, to examine the surrounding space. True, he still does not move far from the nest. At this time, congenital indicative reactions, conditional defensive reflexes. During this period, the cubs can already develop conditioned reflexes to any signals from the external and internal environment, but the rate of their formation and the duration of their preservation are still small. As it develops, the growing cub begins to contact more and more with other family members. A mass of new impressions falls on him, he must learn to navigate in the world around him, gradually understand what should be feared and what should not. During this period, the cubs are still strongly attached to each other and to their den. The most important moment in the formation of their behavior during this period is the formation of the ability to communicate with each other. Therefore he is period of primary socialization(some authors call it the first period of socialization). This period is of particular importance for species that maintain family relationships for a sufficiently long time (Figure 13.3).

In domestic dog puppies and other canines, this period begins when they are about one month old. By this time, the main physiological functions have been formed, but the intensive growth of the animal and milk feeding continues. During this period, the baby's nervous system is most susceptible to the influences of both favorable and unfavorable environmental influences. Their physical activity sharply increases. A daily rhythm of motor activity characteristic of the species is formed. As the activity of the cubs increases, the number of environmental stimuli acting on them also increases. In this regard, research activity in the form of orientation-research reflex, named by IP Pavlov "what is it?" Under the action of any stimuli, puppies become alert, raise their ears, head, approach new objects, lick them, take them into their mouths, and gnaw. Manipulating the surrounding objects is the most important condition for further improving a variety of skills. Motor exercises have a beneficial effect on the development of the organs of movement and on the work of the heart, lungs, and brain of animals.

For normal development, the calf needs to receive as much information as possible and contact with all kinds of diversity of the environment. Restriction of movement and various kinds sensory deprivation during this period leads to developmental delay and irreversible changes in the formation of behavior. Play activity plays an extremely important role in the formation of the animal's mental activity and the formation of its social behavior.

Active contacts in the form of play and aggressive clashes between cubs begin very early, often even before the eyes are opened. The development of play activity goes in parallel with the improvement of motor and orienting-research activity. At this stage of development, they occupy almost the entire waking time of the calf. In the process of contacts with family members, he intensively learns the basic "laws of community". Communicating with his peers, the cub masters the laws of hierarchy. This happens during joint games, and during the struggle for food, the best place to rest, etc. The dominance of the cubs at this time has the character of a "swing": today - one, tomorrow - another, depending on their physical condition and relationships with their parents, who sometimes quite intensively intervene in games and conflict situations. Positive and negative emotions play an important role in regulating the behavior of the growing cub.

Cubs of most species at this age maintain stable contact with their parents and brothers and do not move any significant distance from the nest. Thus, the process of socialization at this stage of development affects mainly relationships within the family.

Rice. 13.3.

a - the grown up foxes begin to leave the burrow; b - cubs beg for food from their mother

The life of brood birds and mature-born mammals actually begins precisely from this period of ontogeny. In chick birds, this period corresponds to the time when the parents still continue to take care of and feed the chicks that have flown out of the nests.

Juvenile period

The further the cub moves away from the nest, the more live and nonliving stimuli he has to face. Further socialization already affects relationships with other representatives of their own species, with representatives of other species and all the diversity of the surrounding world. In other words, he enters a large community and must master the laws existing in it. The duration of this period is also very different for representatives of different species. This period is called juvenile, adolescent or preadult (the period preceding growing up). It continues until puberty. During this period, the young of most species stop feeding on breast milk. They begin to make rather long journeys from their native nest, to visit neighboring territories. Babies' teeth change, and this process is accompanied by a number of physiological features. Typological features of temperament and character, defensive reactions are formed. There is a preparation for puberty, which is manifested in "sexual games", which are of great importance for further sexual behavior. This is especially true for males.

This period is a natural continuation of the period of primary socialization. All processes associated with the formation of the social behavior of the animal continue. However, if in the previous period the cub masters mainly the rules of behavior in the family, then during the juvenile period he must learn well the norms of behavior in a complex society in which he will exist throughout his future life. Thus, the period of primary socialization can be conditionally compared with the period of preschool education of a child in a family, and socialization in the juvenile period - with upbringing and complex "grinding" of relationships in secondary school. Because of this, the juvenile period is often called the socialization period (in some manuals it is called the second period of socialization ), since it is at this time that the relationship between the growing calf and its social environment is formed (Fig. 13.4).

Rice. 13.4.

Formation of typological features

During this period, the formation of typological characteristics takes place in the young. At an early age, all cubs behave very similarly - they are outgoing, playful, excitable and have few distinct personality traits. So, for example, in puppies, differences in the basic properties of the nervous system are found by the end of the second month of life, but they acquire the clearest expression by three or four months. A similar process can be observed in the young of other species.

Youthful caution. At the beginning of the juvenile period, most pups begin to show a passive-defensive reaction, which dramatically changes behavior and determines all subsequent characteristics of higher nervous activity. The passive-defensive reaction in a growing cub is a completely natural phenomenon. In the ego time, he is already largely independent, he has to deal with many objects and phenomena that are not yet familiar to him. Being cautious about them is perfectly normal. This passive-defensive reaction is sometimes referred to as adolescent caution. Gradually, as the cub assimilates the laws of the surrounding world, it decreases.

The extinction of a passive-defensive reaction to insignificant signs is actually similar to habituation, which ensures the adequacy of the body's reactions, eliminating all unnecessary, unnecessary reactions that do not bring tangible benefits and without affecting only the most necessary ones, which saves a lot of energy. The animal is able to tolerate any influences that it encounters every day on its territory, and not to respond to them with either an indicative or defensive reaction, adapt to herd mates and limit its reactions that arise in their presence to only really necessary ones. Due to habituation, the social behavior of any animal community is standardized, which simultaneously leads to an exacerbation of the perception of the most important key stimuli.

As numerous experiments show, sensory and social deprivation plays a very negative role in shaping behavior during this period. The study of the formation of the defensive behavior of dogs showed that puppies raised in isolation show a pronounced passive-defensive reaction in relation to all unfamiliar objects and phenomena. The severity of this reaction is in direct proportion to the excitability and balance of the animal's nervous system. Intensive familiarization of the growing calf with all the diversity of the habitat during this period is imperative.

In the juvenile period, the further development of various communication methods by the young continues intensively.

The role of play in the development of behavior. Play activity has an extremely important role in the formation of the psyche and the development of social behavior of an animal. The games of young and young individuals are very diverse and cover all spheres of the animal's behavior during its growing up. At a certain stage of ontogenesis, the main part of the entire complex of adolescent behavior consists of games. In particular, it is precisely for this reason that the juvenile period of ontogeny is sometimes called the play period. Well-developed play behavior is observed in animals with a sufficiently high level of psyche development (Fig. 13.5). It can be fully observed in mammals and birds with a high level of mental development.

Rice. 13.5.

a - social game; b - group locomotive game

During the game, a young animal acquires a variety of information about the properties and qualities of objects in its environment. This makes it possible to concretize, clarify and supplement the species experience accumulated in the process of evolution in relation to the specific living conditions of an individual. It is important to emphasize that any manipulation, especially game manipulation, always includes a research component. Game manipulation of objects is especially stimulated by the appearance of new or little-known objects. The development of motor characteristics is associated with the study of the environment. We can say that the ever-increasing accumulation of information about the components of the environment is a function of developing motor activity, the orientation of which in time and space, in turn, is carried out on the basis of this information. It is in this that the unity of the motor and sensory elements of behavior developing in the course of play finds its expression.

The cub can play alone. At the same time, he grabs various objects in his teeth, transfers them from place to place, tries on a tooth, throws them into the air, and scratches with his paws. These games are called manipulative. In the process of such games, the animal gets acquainted with the properties of objects, masters motor and research skills.

Often, the cub begins to run deliberately quickly, describing many zigzags, making high jumps. It - locomotive games, their main purpose is the formation of motor skills and the mastery of the laws of motion. They can be both single and group. Games of this type include various forms of game wrestling, joint jogging, hide-and-seek games, and catch-up games. This is how the future hunting behavior is trained. Animals run after each other, changing places, hiding, hiding and looking for each other, fighting, growling ferociously at the same time. Sometimes one cub grabs an object in its teeth and, running away, invites its fellows to take possession of it. In the same way, puppies and adult dogs often play with people, offering a variety of toys, sticks and balls, and then running away with them. Games of this kind are called trophy (fig.13.6).

Rice. 13.6.

Group behavior in animals is formed to a large extent in the course of play. This role is played by joint games. they should be understood as such games in which there are concerted actions of at least two partners. Joint games are found only in animals, which are characterized by developed forms of group behavior. Play is also of great importance for the formation of hierarchical relations. So, puppies and foxes already at 35–45 days of age begin to defiantly attack each other with signs of dominance and intimidation. At the same time, their social roles are constantly changing. Gradually, puppies practice the language of facial expressions and gestures, postures of dominance and submission, which are of great importance for adult dogs. Later, ritualized forms of communication arise from them.

The consistency of the activities of gaming partners is based on mutual innate alarm. These signals serve as key stimuli for play behavior. These are specific postures, movements, sounds that notify the partner about the readiness for the game and "invite" him to take part in it. In canine pups, the invitation to play is carried out with the help of a special ("play") manner of approaching the partner, accompanied by a specific swinging of the head from side to side, bending down the front of the body, swinging it or small jumps from side to side in full view of the partner, lifting the front paw towards the partner, etc. At the "flirting" cub, longitudinal folds appear on the forehead at the same time, and the auricles are turned forward. Less important are signals that prevent a serious outcome of the play struggle, and allow the animals to distinguish play from non-play. Without such a warning that the aggression is "fake", the game struggle can easily turn into genuine one. These signals are clearly related to the postures and movements of pacification during genuine clashes of adult animals; they mainly create a general play situation.

On the example of animals of different species, it has been shown that cubs who grew up in isolation and deprived of the opportunity to play became incapable of social contacts, their behavior was greatly distorted. When young of different species are reared together, for example, at the young animals' grounds in a zoo, they prefer games with individuals of their own species, but in their absence, compensatory games with representatives of other species and with humans may occur. Therefore, for the normal development of further behavior, a cub growing alone must be provided with partners as close in age to play as possible.

Raising cubs by parents

In fact, the juvenile period is the most difficult for the young of most species, since it is at this time that they prepare for independent life. During this time, the baby develops both physically and intellectually. He very actively learns the world and learns to respond to it adequately. In adolescence, the baby is in the position of a baby elephant from R. Kipling's fairy tale "Why does the baby elephant have a long nose?" For example, adult dogs punish a puppy for inappropriate actions, they can knock him down, growl scary, but usually do not bite. Interestingly, they often exhibit exaggerated positions of dominance and intimidation without, however, causing physical harm to the puppies. A cat, if she is a member of a dog pack, when a cheeky puppy gets tired of her harassment, can take a threatening pose and hit him with a paw, without releasing the mines. The point of these exaggerated actions is for the baby to learn them better and remember them for a long time. The puppy in such a situation squeals loudly and demonstrates a posture of submission, thereby extinguishing the teacher's aggression.

In nature or in conditions close to it, young at this age still maintain direct contact with their parents. They constantly monitor the behavior of young animals and often direct their activities in the right direction. So, conflicts between cubs, when they take on the character of a real fight, are immediately stopped by adults. Sometimes adults provoke an attack of the whole brood on a "guilty" cub of something. The author once had to observe how a family group of dogs crossed a busy Moscow highway, consisting of a pair of adult dogs and three puppies of three to four months of age. The whole group stood on the side of the road, adult dogs closely watched the traffic. At that moment, when there were few cars, adult dogs began to move across the street, and the puppies did the same, exactly copying their behavior. In the middle of the street one of the puppies rushed about, lost the pace of movement and was in danger. Fortunately, everything ended well, and the frightened puppy caught up with his group, literally emerging from under the wheels of the car. Adult dogs, who had already crossed the street, carefully watched what was happening, the puppies sat without moving next to them. When the straggling puppy approached its relatives, both adult dogs rushed at him, knocked him down and, without biting, roared for a long time standing over him. Then the whole group set off in the direction she needed: a bitch was walking in front of her, a loser puppy followed her, then two other puppies, and a dog closed the procession. This was clearly an educational act.

Puberty

At this point, young mammals have basically completed their growth period. The change of milk teeth to permanent ones is coming to an end. Regulatory mechanisms and functional systems are being improved and developed. In males, spermatogenesis begins, and in females, oogenesis. In dogs, this occurs at an average age of 8–12 months. In animals of the middle lane, the breeding season of which is confined to the spring period, the onset of these processes may be somewhat delayed. So, for example, most small predators actually become adults and independent by the onset of autumn, and their gonads begin to function only before the breeding season, i.e. at the end of winter.

In female animals, whose reproduction is not seasonal, puberty can occur in any season. Outwardly, the maturation of animals is manifested in the fact that they begin to intensively mark the territory. By the time of puberty, mammals more or less master the skills of obtaining food, saving from danger, finding shelter from bad weather. Further improvement of these forms of behavior continues later. In fact, during this period, the formation of the behavior of an adult animal and its inclusion in society takes place. This gives reason to consider this period as the third period of socialization... Great changes during this period are taking place in social behavior. By the time puberty is completed, the animal must clearly master all the nuances of communication, be able to correctly use the signals of dominance and submission, and respond to them correctly. The attitude of adults to young animals is also changing. If adults simply bring up the growing cubs, then with the onset of puberty everything changes. The young animal seeks to occupy a higher and higher place in the hierarchy and seriously determine its place in the family group. N. Tinbergen studied the behavior of sled dogs in Greenland. These dogs live in groups at camps and exhibit a well-expressed territoriality of behavior. Puppies born to these dogs, before puberty, move freely throughout the territory, go to other people's areas and communicate with peers and adult animals. Adult dogs do not show serious aggression towards strangers, although they sometimes raise them. After the onset of puberty, group members no longer allow outside adolescents into their territory, they must exist within the boundaries of their site. In case of disobedience, they are severely punished by the owners of the site.

The change in behavior with the onset of puberty is very noticeable in the example of domestic dogs. A puppy taken away from its mother and ending up in the house of a new owner perceives him as a parent, and therefore as a pack leader, his family as his pack, and his house as his home. He is socializing with a person. His relationship with family members begins to take shape as if he grew up in his own canine family. He begins to try himself in the field of hierarchical relationships, manifests territoriality, etc. The infantilism inherent in most dogs helps that children's affection for parents and complete obedience to the leader are transformed into love and loyalty to the owner.

As they grow older, a large puppy often begins to feel his physical superiority over the human educator and tries to win his right to the surrounding territory. A potential dominant puppy will try to establish hierarchical relationships with those around him. If he is not immediately given to understand that the role of the owner as a leader is unshakable, then conflict situations are inevitable. If the owner and members of his family show him that they are afraid of him, then the further stay of such a dog in the house becomes dangerous to the health, and sometimes the life of others. It is for this reason that many owners have to part with large dogs at the age of one. At the same time, the territorial and hierarchical claims of small dogs, since they do not pose a direct threat to the lives of the people around them, sometimes even seem funny to the owner. As a result, among small dogs more often than among large ones, there are vicious, barking and biting owners a lot. It should be borne in mind that although the dog begins to recognize the people around it as members of the flock, during all periods of ontogenesis it absolutely needs social contacts with dogs. Their absence leads to the fact that the dog becomes incapable of normal contacts with its own kind, its sexual behavior is disturbed, it becomes aggressive towards all dogs, regardless of gender, or, conversely, begins to fear everyone in panic. As a result, abnormalities in the dog's relationship with the owner easily arise.

The same thing happens with other animals, such as domestic ungulates. However, among domestic animals there is a constant selection for loyalty to humans and controllability, therefore, with proper upbringing, they become completely controllable and retain this quality throughout their future life.

At the same time, wild animals raised by man, as they grow older, more and more seek to show dominance over their teacher and sooner or later go out of obedience. For this reason, stories related to the keeping of predatory animals at home very often end tragically.

Puberty is also very difficult for children. The teenager feels like an adult, he is trying in every possible way to assert himself. He begins to resist the requirements that he previously willingly fulfilled, takes offense and protests when they limit his independence, take care of him "like a little", control, demand obedience, etc. A teenager develops a heightened sense of his own dignity, he realizes himself as a person who cannot be suppressed, humiliated, deprived of the right to independence. He restricts the rights of adults, wants to expand his mores and in every possible way claims to be equal. Sometimes this leads to severe conflicts with others, and especially with members of your family. It is during this period that the transition from the typical childhood type of relationship between an adult and a child to a qualitatively new one, specific for the communication of adults, takes place. The biological basis for such changes in human behavior is the formation of hormonal levels that occur during the period of growing up.

Establishment of sexual behavior

During the juvenile period, sexual games, in the process of which the training of individual components of this complex behavioral act takes place. The study of the influence of the conditions in which young calves were raised on subsequent sexual behavior showed that for the formation of normal sexual behavior, animals need contact with their peers during this period. It has been shown experimentally that male rats need early play communication with other rats to fulfill the reproductive function. These games contain the basic motor elements of adult male behavior. In minks, males learn normal communication with a mating partner during joint games from 10 weeks of age.

The significance of the joint games of cubs for the later life of an individual is especially clearly manifested in monkeys. The harmful effects of depriving young monkeys of the opportunity to play with peers (or other animals) are convincingly evidenced by the experiments of many researchers, in particular Harlow and his collaborators. As in other animals, these disorders are found in adults primarily in their inability to communicate normally with their own kind, especially with sexual partners.

A huge role for the formation of normal sexual behavior is played by correct sexual imprinting. It ensures future intercourse with a sexual partner. The animal learns to recognize the hallmarks of a future sexual partner at the early stages of postnatal development. In this case, the imprinting of typical signs of a sexual partner should take place in the cub in the form in which they appear before him already in an adult, sexually mature state.

Basically, this process takes place in males, who, in the image of their mother and sisters, capture the characteristic features of the females of their species. This is greatly facilitated by the fact that before puberty, and sometimes even before the breeding season, young males and females of most species have almost the same appearance. Moreover, in many species, males acquire signs of sexual dimorphism only during the mating season. So, for example, males of Turukhtan waders grow lush, brightly colored feather collars at this time. The rest of the time they are practically indistinguishable from females. After the breeding season, the drakes of many species of ducks lose their rainbow coloration. Thus, exactly at the time when the young are growing up, all representatives of this species are as standardized as possible.

The process of sexual imprinting, in contrast to the imprinting of the image of the mother and the object of succession, continues for quite a long time. In other words, sexual imprinting has a rather extended sensitive period. Thus, it was shown that in male wild ducks the sensitive period of sexual imprinting extends from the 10th to the 100th day after hatching, but the optimal period is limited to 10–40 days. If during this period a male chick saw only a female of a different species, then upon reaching puberty it will look after only females of this species, leaving the ducks of its own species unattended. Even clearer results are given by experiments with replacement of clutches, in which chicks are raised from birth by adoptive parents. Experimenters use this to obtain interspecific hybrids.

The phenomenon of sexual imprinting has also been described in mammals. However, apparently, their sensitive period begins with the period of imprinting the image of the mother. In many mammalian species, interspecific crossing, like birds, is possible only when the male is fed by a female of another species. Perhaps this is due to the fact that for mammals the leading role in the reproduction process is played by chemocommunication.

Sexual imprinting plays a colossal role in ensuring reproductive isolation in nature. But, on the other hand, for rare species it can turn out to be harmful. So, for example, in a male of a species with a low abundance, which grew up in a small brood, sexual imprinting of the image of a female of a more common species can easily occur. Subsequently, such a male will be doomed to celibacy, since he will not react to females of his own species, and females of another species will reject him. This can lead to a further decrease in the number of the rare species.

In animals raised under artificial conditions, a person is often the object of sexual imprinting. This circumstance often turns out to be an insurmountable obstacle when trying to obtain offspring of rare animals in zoos.

So, the main feature of sexual imprinting is that the final result appears only with a long delay, because the animal learns to recognize the distinctive features of the future sexual partner at an early stage of postnatal development. Basically, sexual imprinting is observed in males, and the distinctive features of their mothers are recorded in them as "samples" of females of their own species. Consequently, the recognition of the characteristics of the female of the same species is superimposed on the innate recognition of general species-specific characters.

Formation of maternal behavior

Sexual imprinting is also possible in females. Thus, it was shown that females of wild ducks reared with males of a different species in the future also showed sexual preference for them, and not for males of their own species. However, in females, sexual behavior is determined to a much greater extent by innate mechanisms and more complex learning. In particular, numerous experiments on monkeys have shown that females raised in artificial conditions are unable to carry out normal newborn care. The Harlow couple raised 55 monkeys without their mothers. When they became sexually mature, only one monkey showed interest in a sexual partner. Among the 90 other monkeys raised with the dummy, only four became parents, but they also treated their cubs very badly. Some of them spent all their time sitting in one place, in complete indifference to others. Others adopted strange postures or wriggled unnaturally. Lack of maternal care left their imprint on them for life.

In early childhood, young rhesus monkeys spend most of their time in their mother's arms, tightly pressed against her in a belly-to-belly position. During this period, two groups of reflexes play the main role. The first includes reflexes associated with feeding, as well as the "clinging" response and, possibly, other motor reflexes that help the cub to stay near the nipple (for example, the urge to climb up). The second group includes motor reactions that help the cub to establish and maintain a belly-to-belly position. However, this behavior of the young would be completely ineffective if there was no passive or active assistance from the mother. The mother cradles, feeds with milk, searches her cub, keeps him near her and returns if he has moved far. In the experiments of I. Harlow it was shown that this behavior is determined by the mother's own experience at an early age. Monkeys raised with artificial wire "mothers" (Fig. 13.7) do not develop adequate maternal behavior. Rhesus babies seem to learn to recognize their mother during the first two weeks of life.

Rice. 13.7.

Family breakdown

As young people become more independent, parental attachment to them gradually diminishes. The individual distance between parents and growing children is gradually increasing. In the end, the parents begin to drive away the young from themselves, thereby accelerating their transition to an independent life, which in different species occurs at different times. Young wild pigs remain with their mother until they reach puberty, young tigers - until the mother's next estrus, which occurs only after two to three years. Wolf broods keep with their parents for a long time.

The female brown bear walks with the cubs throughout the summer and lays down in the den with them in the fall. Marmots hibernate in families. Until next spring, cubs of lynx, otter and many other relatively large animals remain with their mother.

The disintegration of families of small species occurs by the fall or even earlier. So, in murine rodents, broods disintegrate 1–2 months after the birth of cubs. The timing of the disintegration of families largely depends on the availability of food. The abundance of food postpones the disintegration of families. As food resources in the burrow area are depleted, young arctic foxes, no longer looked after by their parents, lengthen their hunting trips more and more, stay away from the pore for a long time and, finally, completely part with it. In the initial period of independent life, young animals are very careless, and a significant part of them become prey for predators or die from random causes.

In tundra arctic foxes, the early breakdown of families due to lack of food is a common occurrence. Young animals, deprived of the care of their parents and still little adapted to independent existence, often starve, develop poorly and die in large numbers. In accordance with the high requirements for the food supply, large families, as a rule, disintegrate faster than small ones. In many mammalian species, the disintegration of the family begins with the departure of the female, after which the brood disperses. Thus, young animals pass to independent life at different ages.

Resettlement of young animals

Having started with disorderly movements, settlement can gradually acquire direction and turn into migration. The high mobility of populations of many species, due to the dispersal of young, constant mixing of individuals originating from different broods, has significant biological significance. First of all, this prevents closely related crossbreeding (inbreeding). Resettlement makes it possible to most fully develop all areas suitable for the life of the species and ensures a relatively uniform distribution of individuals and pairs in biotopes similar in terms of conditions.

Period of morphophysiological maturity

Physiological maturity in animals begins with first heat in females and the beginning sustainable spermatogenesis in males. The development of the gonads is stimulated by the pituitary gonadotropic hormone. Sex hormones in the blood of babies appear quite early and cause "sexual games". A gradual increase in their level in the blood contributes to the onset of full-fledged spermatogenesis. Intensive release of gonadotropic hormone by the pituitary gland inhibits and gradually stops the growth of the animal. However, in many animals living in groups, these processes can be temporarily suppressed by hormonal or mental influences on the part of dominant individuals.

Orbeli L.A. Questions of higher nervous activity. M .; L., 1949.
L. V. Krushipsky Biological foundations of rational activity: evolutionary and physiological and genetic aspects of behavior. 3rd ed. M., 2009.

According to the accepted periodization, the juvenile period begins after birth and lasts up to 21 years for women, and up to 22 years for men.

The first month of the baby is considered the neonatal period. The baby's posture at this time resembles the position of the fetus in the uterus. The baby sleeps most of the day, wakes up only at the time of feeding. Caring for a child requires strict adherence to the feeding time and preferably with mother's milk, high purity, and a temperature of at least 20 ° C.
From the first month to a year, the period of time is called breast.

During the first year of life, many changes in the motor system occur in the child's body. At the end of the first month, he tries to straighten his legs, at a month and a half he raises and holds his head, at six months he sits, and at the end of the first year of life he tries to take the first steps. The child's psyche also develops during this period. At the 2nd month, the child smiles when the mother appears or when showing bright pictures; by the 4th month he takes toys in his mouth, examining them, begins to distinguish between adults. In the second half of infancy, the child begins to understand many phrases of the parents. The active movements of the child at this time contribute to the development of the muscular and skeletal systems, the better provision of the body with nutrients and oxygen, i.e. strengthening metabolic processes in the child's body, and most importantly, they normalize the activity of the nervous system. Water and air procedures are necessary during this period for the child.

Three rules must be followed by adults when caring for a child during this period: gradualness, repetition, systematicity. A clear mode of a child's life will develop conditioned reflexes in him, the formation of which makes it possible to develop in a child life skills that ensure a high stability of the body and the action of unfavorable factors.

Early childhood- period from one year to 3 years. During this period, the child grows vigorously, eats the same food as adults, he has a desire for independence and self-respect. He masters many new movements, while playing he imitates adults.

Preschool period- period from 3 to 7 years. During this period, children show great interest in the world around them. Curiosity is so great that this period is also called the stage of questions: where? when? why? why? During this period, the brain continues to grow, internal speech is formed. An external manifestation of this is the child's conversations with himself and with toys. For a child during this period, play is important. It occupies the same place as that of an adult in sports and work. Games develop the child and encourage him to be creative.

School period- period from 7 to 17 years. This period is subdivided into early(7-11 years old), average(11-15 years old for boys and 11-14 years old for girls) and older(15-17 years old). For the early school period, the main thing is already study. This is a serious, intense work in mastering written language, in educating collectivism, in learning new things about the world around us, in assimilating the experience accumulated by many generations of people. All this contributes to the harmonious mental, physical and volitional development of schoolchildren.

Adolescents, as well as older schoolchildren, are characterized by an accelerated pace of physical and sexual development, called acceleration. For example, in the 20s of our century, the growth of 14-year-old boys reached an average of 145.4 cm, in the 70s, growth reached 162.6 cm, and their body weight increased by 13.5 kg on average. The average growth and body weight of girls also increased markedly. The reasons for acceleration have not yet been fully studied, but it has been found that the physical development of modern children does not entail their moral and social maturation.

Psychological maturity- this is the moral stability of girls and boys, self-control of behavior in the family and society. Social maturity- this is a conscious attitude of a person to reality, this is the completion of education by a person, the beginning of labor activity, economic independence, this is when it is necessary to fulfill a civic duty to the state.

2. Juvenile stage

The stage of youth in seed plants begins with the germination of seeds or organs of vegetative propagation and is characterized by a rapid accumulation of vegetative mass. Plants during this period are not capable of sexual reproduction.

In the juvenile period, seed germination (or vegetative primordia) and the formation of vegetative organs are carried out. Germination, in turn, is divided into the phases of seed swelling, hatching, heterotrophic seedling growth, and transition to autotrophic feeding.

At the end of the dormant period in the seeds, the absorption of water by them serves as a starting factor for germination. This absorption is carried out due to the increase in some cases of the permeability of the seed coat to water and due to the hydration of biopolymers in the cells. As a result, oncotic pressure (swelling pressure) develops and the seed covers rupture. Swelling practically does not depend on temperature, oxygen content, lighting.

Picking begins when the seeds reach a critical moisture content (40 - 65% in terms of wet weight), and occurs by stretching growth of the embryonic root itself or hypocotyl, as a result of which the root tip is pushed out of the seed. Cell division usually occurs later. The growth by stretching of the cells of the embryonic axis is due to a decrease in the ABA content during seed swelling. Root emergence secures the germinating seed in the soil and improves water absorption.

Shoot growth begins after the root. Germinating in the dark (in the soil), both the root and the shoot are oriented primarily by the gravitational vector, while the root deepens into the soil, and the shoot is directed towards the light. The growth of the axial parts of the seedling embryo is supported by phytohormones. Moreover, in cereals, IAA and cytokinins first enter the embryo from the endosperm, HA is released from the bound state in the embryonic axis, and after a few hours the synthesis of gibberellins in the scutellum is induced. The epithelial cells of the scutellum begin to digest storage substances in the endosperm. The cells of the aleurone layer, activated by gibberellin, are connected to the digestion process. Acidification of endosperm tissues due to the operation of H-pumps creates conditions for acidic digestion and for the absorption of starch and protein decomposition products by epithelial cells. Epithelial cells begin to stretch and grow into the endosperm, carrying out a heterotrophic way of feeding the growing embryo and seedling.

The growth of the embryonic root is accompanied by the appearance along it of zones of division, elongation and differentiation of cells. The root itself begins to synthesize cytokinins and HA, which are sent to the shoot. The shoot is elongated due to stretching of the hypocotyl (in beans, pumpkins, etc.) or the mesocotyl (in cereals). The leaves do not develop and the hypocotyl in its upper part bends strongly like a hook, which facilitates its movement in the soil. IAA is synthesized in the kidney in dicotyledons and in the apex of the coleoptile in cereals.

When the etiolated shoot reaches the surface of the ground, a light-growth and photomorphogenetic reaction occurs: the growth of the hypocotyl or mesocotyl is sharply suppressed, the growth of the epicotyl (the first true internode) and leaves is enhanced. The ethylene content in the area of the hook is reduced and the hook is straightened. The plant turns green and switches to a phototrophic type of nutrition.

Due to the further growth of the main, lateral and adventitious roots and the formation of shoots due to an increase in the number of metameres, branching, growth of leaf blades, and thickening of the stem, the plant accumulates a significant mass by the end of the juvenile stage.

The duration of the juvenile period is not the same for different plant species: from several weeks (annual grasses) to tens of years (in arboreal plants). Seedlings are unlike adult plants in many ways. Differences are often clearly visible in the shape of the leaves (cotton, cucumber, morning glory, etc.). In some plants, differences are also observed in the internal structure. Thus, in fern seedlings, the conducting system is organized more simply than in adult plants. Juvenile plants have a less powerful apical meristem. In some cases, the growth pattern of a plant can also serve as a morphological sign of juvenility. Thus, ivy in the juvenile state is a climbing shrub, and upon transition to an adult state it forms a vertical bush.

The stage of youth is characterized by a complete absence of flowering or flowering is poorly expressed even under the most favorable conditions for this. The role of competence is clearly manifested here. In this case, the juvenile plant is not competent to the factors causing the establishment of organs of sexual or vegetative reproduction. This may be due to the absence of receptor proteins involved in the induction of generative development in the target organs that perceive hormones.

However, the absence of flowering in itself cannot serve as an indicator of juvenility, since many plants, being in a mature state, do not bloom for a long time without the necessary conditions for this. Therefore, the described morphological characters serve as more reliable criteria for juvenility.

Juvenile plants are characterized by a significantly greater capacity for root formation, which has long been used in horticultural practice. It is assumed that the better rooting rate of juvenile cuttings is a consequence of the higher content of auxins. However, the auxin treatment of adult cuttings does not cause a return to the juvenile state in terms of morphological characteristics, although it enhances the ability to form roots.

The juvenile state is supported by a specific hormone ratio. In some cases, gibberellin treatment leads to the formation of juvenile leaves or prolongation of the juvenile state.

The transition from juvenile to mature growth is most clearly seen in woody plants. In beech, for example, it is possible for all phases of juvenile development to coexist until maturity. This property of woody plants is widely used in horticulture, when cuttings are taken from the base of the seedling to obtain juvenile plants, and cuttings taken from the upper, more mature tiers are rooted or grafted to obtain fast flowering and fruiting plants (Polevoy, 1989).

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Postembryonic development of animals is subdivided into three periods:

4.1. Postembryonic period of animal development

Growth and shaping period(pre-reproductive )

This period is characterized by the continuation of organogenesis that began in embryonic life and an increase in body size. By the beginning of this period, all organs reach the degree of differentiation at which a young animal can exist and develop outside the mother's body or outside the egg membranes. From this moment, the digestive tract, respiratory and sensory organs begin to function. The nervous, circulatory and excretory systems begin their function even in the embryo. During the period of growth and formation, the species and individual characteristics of the organism are finally formed, and the individual reaches the sizes characteristic of the species. Later on other organs, the reproductive system differentiates. When its formation ends, the second stage of postembryonic development begins.

Maturity period(reproductive).

Reproduction takes place during this period of maturity. The duration of this period is different for different species of animals. In some species (mayflies, silkworms) it lasts only a few days, in others it lasts for many years.

Old age ( post-reproductive).

It is characterized by a decrease in metabolic rate and organ involution. Aging leads to natural death.

4.2. Postembryonic period of human development

Postembryonic postnatal) period of human development, otherwise called postnatal, is also subdivided into three periods (Fig. 5):

Juvenile (before puberty);

Mature (adults, puberty);

Old age ending in death.

In other words, it can be said that for humans it is also possible to distinguish pre-reproductive, reproductive and post-reproductive periods of postembryonic development. It should be borne in mind that any scheme is conditional, since the actual state of two people of the same age can differ significantly. Therefore, the concept of chronological (calendar) and biological age was introduced. Biological age is determined by the totality of metabolic, structural, functional characteristics of the organism, including its adaptive capabilities. It may not correspond to the calendar one.

Scheme 5

4.2.1. Juvenile period

According to the accepted periodization, the juvenile period begins after birth and lasts up to 21 years for women, and up to 22 years for men.

The first month of the child is considered the neonatal period. The baby's posture at this time resembles the position of the fetus in the uterus. The baby sleeps most of the day, wakes up only at the time of feeding. Caring for a child requires strict adherence to the feeding time and preferably with mother's milk, high purity, temperature not lower than 20 ◦ C.

From the first month to the year, the time period is called chest.

Middle school the period is also called adolescence. Children undergo a profound restructuring of the activity of all organs and physiological systems. This is due to puberty, with the intensive formation of sex hormones, which entails the peculiarities of physical and physiological development, both in boys and girls. In adolescence, the development of speech ends, the formation of character and the moral formation of the personality takes place.

Distinguish, thus, physiological, psychological and social maturity. Physiological maturity- This is the puberty of the body. The term for reaching physiological maturity is individual. It depends on climatic, hereditary and other factors. Psychological maturity- this is the moral stability of girls and boys, self-control of behavior in the family and society. Social maturity- this is a conscious attitude of a person to reality, this is the completion of education by a person, the beginning of labor activity, economic independence, this is when it is necessary to fulfill a civic duty to the state.

The juvenile state is supported by a specific hormone ratio. In some cases, gibberellin treatment leads to the formation of juvenile leaves or prolongation of the juvenile state.