Periodization of ontogenesis, Prenatal period, Humoral connection...

Periodization of ontogeny

So, in the process of ontogenesis, every animal undergoes several periods of development. Each period of development, consisting of a number of phases, is characterized by a certain relationship of the organism with the environment. Between the phases there are turning points, called critical periods, which are characterized by a special sensitivity to completely defined external influences.

There are a number of classifications of periods (stages) of development, which differ somewhat from each other. The duration of individual stages of development can differ both in animals of different species and in individuals.

There are two main periods in the ontogeny of behavior: prenatal and postnatal. This division allows us to consider the general patterns development of higher vertebrates. Each of the periods is divided in turn into a number of smaller stages, the duration of which can vary significantly among representatives of different taxonomic groups.

Prenatal period

The development of animal and human behavior begins already in the embryonic period. Developing in the womb of the mother or in the egg, the calf produces a variety of movements that are elements of future motor acts, but are still devoid of the corresponding functional significance. As research has shown, intrauterine movements affect the coordination of physiological processes associated with muscle activity, and thus contribute to the preparation of the behavior of the newborn. This process is especially important for young children. So, newborn lambs and kids can not be tired of running for two hours in a row. This possibility is due to the fact that during the embryogenesis through exercise, coordination of all functions, including those necessary for carrying out such intensive activities at the very beginning of postnatal development, was formed.

Experiments of the famous American scientist Qing Yang Kuo, conducted on chick embryos, are recognized as classic experiments on the development of behavior in the embryonic period.

To be able to directly observe the movements of embryos, he designed and carried out truly virtuosic operations: moving the embryo inside the egg, inserting the windows into the shell, and so on. Thanks to this, it was possible to observe first the appearance, and then the modification of the movements of the embryo.

Kuo was one of the first to convincingly show that already in the course of embryogenesis there is an exercise of the buds of future organs, the gradual development and improvement of motor functions by accumulating the "embryonic experience" or "embryonic learning." He determined that the first movements of the chick embryo are the movements of the head to and from the chest. Within a day, the head begins to turn to the sides, and these new movements of the head displace the former. According to the scientist, in this way the pecking movements are formed. Kuo concluded that the genetically fixed prerequisites for the formation of behavior can be realized in different ways depending on the specific conditions of embryo development, but the decoding of genetic information, the relation of the embryo to its environment, plays a crucial role in this process. Kuo emphasizes that embryonic learning should not be considered in the traditional aspect, since self-stimulation plays a significant role in the development of embryo behavior.

Embryonic Learning is not from scratch, but is the development and modification of a certain genetic predisposition, the embodiment and realization in an individual life of an individual species experience accumulated in the process of evolution. Many scientists considered the data obtained by Kuo as evidence of the need for training, even for such reactions, which are usually considered congenital. The fact of "embryonic learning" makes an eternal dispute about the "innate and acquired" even more pointless. During the period of embryogenesis, intensive preparation for the subsequent postnatal stages of behavior formation takes place, and in part the formation of the behavioral elements of the newborn by, on the one hand, the development of genetically determined components of activity and, on the other hand, the accumulation of embryonic experience.

Humoral link between the mother and fetus in mammals

The constant connection between the developing mammalian embryo and the maternal organism through the placenta creates very special conditions for the development of embryonic behavior in this group of animals. A new and very important factor is the possibility of an impact on this process from the mother's body, especially the humoral pathway. Numerous studies have shown that the introduction of male sex hormone to pregnant females promoted the appearance of male behavior in the born females at the expense of normal female sexual behavior. Experiments in which pregnant women regularly caused anxiety conditions led to the birth of more fearful and excitable cubs. At the moment, the role of various humoral influences has been studied quite well. The data of the studies convincingly show the role of the influence of the maternal organism on the formation of the behavior of the young in the embryonic period. Accordingly, it is possible to draw practical conclusions that any pregnant female should be protected from possible harmful influences from the environment, including mental stresses.

Acoustic contacts between nestlings and birds' parents

In many bird species, during the last days of incubation, the mother begins acoustic contact with hatchlings not yet hatched. Thus, chicks nesting in bird markets, kaira, learn to distinguish mother's voice from the voices of other murres nesting in close proximity three to four days before hatching. Similar results were obtained for other species of birds, in particular, from a close relative of the guillemot - auks, in many species of ducks, waders and other brood birds. It turned out that the incubating females in response to certain signals given by the chicks in the eggs rise up on the nest, begin to roll eggs from side to side, swell or press feathers, thus adjusting the incubation temperature, etc. It is shown that adult birds feed the chicks with a sound signal at the right time, stimulating the nestling reaction in the chicks and the synchronism of their release from the shell.

In fact, by the time hatching between a chick and an incubating individual, there is already a developed communication system. In addition, acoustic communication during the last days of incubation takes place between chicks, which directly affects the hatching process. Thus, in the partridge of the virgin partridge and Japanese quail, the sounds given by some chicks stimulate the activity of others. As a result, hatching takes place amicably for approximately one hour.

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