Ontogenesis - the development of a specific, single individuals.This process covers the period from the moment of connection of gametes and to the death of the body.Learning all this time span developmental biology.The ontogeny of plants and animals occurs differently in their different taxonomic groups.
As part of this article discusses the development of multicellular animals.Although the main stages of ontogeny, its general patterns are typical for plants.
It starts from the moment when the egg is fertilized by sperm, or otherwise influence is activated.She then begins to break up, that is, there is a division into smaller cells.When the number reaches several hundreds, or even thousands, changing the shape of the embryo.In it appear the rudiments of various organs.In vertebrate embryos first formed intestine, central nervous system, notochord, muscles, and so on. N. The complex of these processes is called morphogenesis.
Behind him or simultaneously with germ cells become resistant features that allow to distinguish them from each other: the chemical composition, structure and form.
As already mentioned, ontogeny - a process that continues after the fetus is born (or hatch).It is manifested at this stage of metamorphosis (for those individuals who are the larval stage), growth, continuous updating of the intestinal wall cells, lymphoid organs, blood.Aging refers to ontogenesis, not all scientists.
What forces control the process so complicated?While there is no comprehensive answer to this question.However, some important regularities of ontogenesis is still installed.
Firstly, work closely together absolutely all the cells of the embryo.Each one "knows" about exactly where it is.For example, if you remove a small part of the whole embryo, the remaining cells immediately start to develop differently according to the situation.In this way, at least partially eliminate the defect and on the fetus can develop normally.Perhaps cells "communicate" with each other through contiguous membrane.
Secondly, the very first beginnings in the bud already affect one another, while encouraging progress in a given direction.For example, in vertebrates this takes place as follows.The rudiment of the chord (notochord) affect the superficial tissues of the embryo, which come into contact with it, and encourages them to form the rudiment of the central nervous system.Such interactions in biology is called embryonic induction.Some of these effects, including the above-mentioned, called substances which diffuse from one to the other germ.Others are impossible without direct contact between the cells of the primordia that interact.For example, induction of another limb amphibians called abduction nerve endings under the skin, or transfer of the embryo of a foreign body.
addition, the specialized cells influences the synthesis of protein, the amino acid sequence in which a set of defined gene.Why not all of them are active, too, is unknown.
Thus, ontogeny - a process that still attracts the attention of scientists, not only biologists and mathematicians, chemists and physicists.They seek to create a theory of the development of a living organism, which then would help to make a number of other discoveries.After examine the ontogeny - this means not only theorize.This work has great practical importance, since the findings may help in the treatment of malignant tumors and other abnormalities from normal development, in the management of the development of animals and plants in the fight against harmful environmental influences.
