Health, Medicine
How post-embryonic development occurs in multicellular organisms
After the body was born, it begins its postembryonic development, which can last from 1-2 days to several hundred years - it all depends on species. It follows that the life span is a species characteristic of all organisms, regardless of the level of organization of such organisms. Postembryonic ontogeny consists of such periods: juvenile, puberty and senile, which ends in death. All multicellular organisms are subject to a direct or indirect type of development.
Principles of direct development
- childhood;
- adolescence ;
- youth;
- the phase of youth;
- stage of maturity;
- old age.
Death completes not only post-embryonic development, but also the individual existence of the organism. It can be of a physiological nature, that is, it may occur as a result of aging, but also as a result of pathological changes that often result in various diseases or traumas.
Features of indirect development
Indirect postembryonic development implies deep changes in the body that occur throughout the period. In animals such processes affect not only certain parts of the body, but the entire body as a whole. Over time, the organs of the larvae disappear, and in their place organs appear that are characteristic of adult animals. Postembryonic development of animals can be of two types: incomplete and complete metamorphosis. In the first case, the insect passes through such stages: the egg, the larva, the imago, and in the second - the transformation of the larva into a full-grown adult occurs through the pupal stage.
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