Individual development of organisms is a set of biological processes that determine the growth and change of cells throughout the entire period of their existence. The generally accepted scientific name is ontogeny. Its main task is to observe, identify the main stages and features of each period, identify patterns, as well as analyze changes and identify factors that these changes can cause.
Individual development of the organism is inherent not only to man, but also to all living beings and plants. The main stages of development are:
- Pre-embryonic development (gametogenesis).
- Prenatal period of development (development of the embryo itself, embryogenesis).
- Postnatal period (development from birth: growth, weight gain,
- Gerontological period (aging).
- Death of an organism (death is not distinguished as a separate stage in ontogeny, but any individual development ends with it).
regeneration, modification).
Considerwe will not discuss the individual development of the plant organism in this short article, but will focus on the development of representatives of the animal world that is closer to man. The stages of development, as already mentioned, do not change in humans and correspond to those indicated above.
Gametogenesis in humans consists of two components: spermatogenesis (maturation of male germ cells - spermatozoa) and oogenesis (maturation of female germ cells - eggs). Fertilization is possible only under the condition of mature germ cells in the male and female individuals. When pathologies occur in fertilization, organisms can form - chimeras, some of which are quite viable.
Human embryogenesis is one of the most important stages. It is divided into the initial stage (0 - 1 week after fertilization), the actual embryonic stage (2 - 8 weeks) and the fetal or fetal stage (9 weeks - birth). It is during this period that vital organs are formed, the body takes shape, genetic or other pathologies can manifest themselves.
Individual development of the organism in the postnatal period consists in the further development of organs, an increase in size and mass, the acquisition of new mental functions, a change in motor activity and the development of its new types.
The postnatal period is the most important in the development of a new person. Its length is about 17 years (from newborn to adolescence). The individual development of the organism in this period is influenced not only by the features due toheredity, but also psychological and social factors. Consciousness, speech, thinking and other processes of higher nervous activity are formed. By the end of this period, new individuals, as a rule, arrive with completed gametogenesis.
Aging of the body is the stage of withering, depletion of all the resources of the body. Irreversible damage occurs in nerve cells, myelin sheaths, the quality of vision and hearing decreases, vital organs “wear out”, skin integuments change, reproduction function is lost and tissue regeneration slows down sharply, etc.
