Sexual reproduction. Sex cells. Hermaphroditism

Sexual reproduction

During sexual reproduction, the genetic information of the two parental organisms is combined, which leads to significant combinative variability. Sexual reproduction is based on the sexual process, that is, the exchange of genetic information between individuals of the same species (conjugation) or its union (copulation).

During sexual reproduction in multicellular organisms, sex cells (gametes) with a haploid set of chromosomes are formed. Gametes merge during fertilization, and a new organism develops from the resulting zygote.

Each daughter organism receives a new combination of genetic information and differs from other individuals of the species. This increases the ability of the species to adapt to the changing habitat and ensures the survival of some of the organisms in strongly changed conditions.

The structure of germ cells

Sex cells are divided into male (motile – sperm, motionless – sperm) and female (eggs).

Spermatozoa of humans and animals differ from oocytes in small size, mobility and structure.

The sperm cell consists of a head, neck and tail. The head contains a nucleus with a haploid set of chromosomes (1n1c) and a small amount of cytoplasm with organelles.

At the front end of the head is an acrosome (modified Golgi apparatus). It accumulates enzymes that dissolve the shell of the egg during fertilization.

In the cytoplasm of the cervix, centrioles and mitochondria are concentrated, which generate energy for the movement of the sperm.

The ovum is usually much larger than the somatic cells. The eggs of fish, amphibians, reptiles and birds reach especially large sizes.

The ovum is round and motionless. It contains a nucleus and a large amount of cytoplasm with organelles. The cytoplasm contains nutrients necessary for the development of the embryo.

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