Fertilization

Fertilization is the penetration of sperm into the egg and their merger process, characteristic for sexual reproduction. Animals fertilization is external and internal. In the first case, sexual products deposited in water (fish, amphibians, echinoderms and others) or on hard substrates (mites and other). Internal fertilization - the egg and the sperm is connected to the inside of the parent body.
Usually the egg is fertilized by only one sperm cell, the nucleus of the other destroyed. The sperm penetrates the ovum through the tiny opening of her shell - micropyle or vypyachivalis meet him "vosprinimaetsya bump". It is immersed head (core) sperm moving to the center of the egg; moving towards the core of the female cells. In the result of fertilization is achieved stimulation of the eggs, its fragmentation, development and education of the embryo (see). In the process of fertilization is the recovery of diploid set of chromosomes (see), the connection of hereditary information of both parents (see Genetics), provided material continuity between generations (see Heredity).

Fertilization is the penetration of sperm or his head into the egg and fusion of nucleus of an egg with the nucleus of a spermatozoon.
Algae, echinoderms, most shellfish, fish, and amphibians fertilisation happens outside the body; other fish and amphibians, and all reptiles, birds, mammals, insects, most of the plants in the body of females. The sperm are introduced into the body female male or allocated to them (Triton) into the environment in spermatophore that female actively incorporates in their sexual way. Better studied fertilization occurring outside the body (sea urchins, molluscs and other). In experiment it is possible to fertilize the corresponding sperm extracted from iceproof eggs of mammals (for example, rabbit). After fertilization, they can be returned to the uterus and continue full development. The fertilization process is regulated by the sex cells produced chemicals that attract the added to the egg (see), and exert more influence on fertilization. These substances are called Gamanov (genogaron and androgony respectively two genders).
In the result of fertilization is achieved stimulation of the eggs, its fragmentation, development, education of the embryo (see), the connection of hereditary information of both parents (see Genetics). The stimulation process connected with the changes of physical and chemical properties of protoplasm eggs and shell that after fertilization becomes more permeable to low molecular weight compounds and impervious to sperm. Before fertilization from the kernel eggs in the ribosome moves RNA, which in unfertilized egg is in a locked state. After fertilization, it participates in the synthesis necessary for the development of egg proteins. Merging the nuclei of maternal and paternal germ cells the number of chromosomes (see) doubles as they do not merge together. Therefore, every cell in the body contains half of the chromosomes received from the father and half from the mother; thus, both parents are equally involved in the transmission of genetic information to offspring (see Heredity) with the help of chromosomes. Animals during fertilization, the sperm enters in the centrosome egg, functioning in the subsequent fragmentation of eggs, and a small part of cytoplasmic organelles (mitochondria and others). Most of the organisms change shell eggs after fertilization prevents the penetration of other sperm into the egg, but many animals in the egg gets a few sperm cells (polyspermia). Usually fertilizes the egg only one sperm cell, the nucleus of the other destroyed. If this does not happen, then there are various anomalies of development of the embryo. If, however, this raises a viable organism, it can often is dispersed - one part of the body has a hereditary properties of the kernel of a single spermin, the rest - other sperm.
X-rays can kill the core of sperm penetrated the egg; this egg developed without the participation of male kernel (ginogina). If you kill the rays of the core of egg development is due to his father's kernel (androgenesis).
Cm. about Reproduction.