The textbook covers the main sections of biology, its tasks in the medical education system and in accordance with the levels of organization of the living - molecular genetic, cellular, ontogenetic, population-species and biosphere-biogeocenotic. The issues of human reproduction, the principles of medical genetic counseling, bioethical aspects of genetics, transplantation of tissues and organs, issues of radiation ecology, the toxicity of living organisms as an ecological phenomenon are considered. The material of the textbook is presented taking into account the achievements of the medical and biological sciences, the relationship of its individual areas is shown.