Since the inception to death as a result of metabolism is the development of an organism – regular changes in its chemical composition and structure. In the process of development to the complicated structure of the maturation of cells, tissues, organs and organ systems. Development takes place heterochronically, Cells, tissues and organs mature simultaneously. From a certain age begins senile change in the structure of, and committed heterochronically. Simultaneously, lifelong change function. The accumulation of quantitative changes in the structure and function leads to the appearance or disappearance of new properties, new characteristics of the organism and its behavior.
As a result of development in certain periods of life change growth of the organism. Height – increasing the size of the developing organism and its organs with a change of their shape, volume and weight. With the growth of increased weight of the active parts of the body as a result of cell proliferation and increased cell-cell elements, their size and weight (“living matter”). Typically, growth stops with reaching maturity. The growth of the mature organism is never proportionate. Growth is regulated by the nervous system and the endocrine glands.
The total increase in the size of the body leads to its elongation. The whole body and parts of it are growing unevenly, heterochronically, there are periods of acceleration and deceleration of growth.
Geterohronizm growth and development due to the phylogeny, but crucial changes in living conditions that determine the qualitative and quantitative differences in motor activity. In accordance with the conditions of existence in each age period changes the nature and intensity of the contraction of skeletal muscles, have a major impact on the growth and development of the organism.