The population is the aggregate of individuals of the same species, occupying a defined, limited habitat, i.e., forming part of this biocenosis (see) or of parasitocenosis (see). For free-living land and water forms the border of territorial distribution, i.e. the area, due to peculiarities of climate, relief and other; for the forms of parasitic barrier settlement of their life cycle and specificity of adaptation (in relation to organisms-masters). The study population is carried out from the positions of environmental and genetic. Ecology studies the devices that ensure the survival of the species and mechanisms of regulation of the number of individuals and population genetics - the phenomena of heredity within this population.

Population (from lat. populatio - population is the aggregate of individuals of the same species, occupying in natural conditions is limited habitat, i.e. part of this biocenosis (see). For the population of parasites habitat serves as the host organism within which formed the so-called parasitoses (see). Cell population is called isolated offspring of one or more cells. Human populations are formed on a geographical, racial, religious, sometimes professional and certain other characteristics.
Because the population is hereditary heterogeneous set of individuals of one species, it is opposed to hereditary homogeneous set of individuals of one species or pure line (see the Clean lines). The set of features of all individuals included in Petrograd, represents its phenotype, the combination of hereditary genes,its genotype. The population is heterogeneous as the phenotype and genotype. Genotype P. develops under the influence of conditions of existence based on the interaction of the factors of heredity, variability, exclusion and selection. There are geographical (spatial), environmental (temporary) genetic barriers to merge populations. Relatively uniform on phenotype populations contain in the heterozygous state a large number of recessive genes. Mutant gene that causes severe hereditary disease in homozygous organisms, is included in Petrograd, if heterozygotes have the advantage. For example, individuals heterozygous for gene sickle cell anemia, rarely fall ill with malaria. Therefore, sickle cell anemia is common in areas of Africa, Asia, Mediterranean, whose population is suffering from malaria. The fight against parasitic and infectious diseases, in particular malaria, may suspend this process include mutant gene in Petrograd, as heterozygous carriers of the gene are losing their benefits.
Practical importance of genetics of P. person is to prevent the birth of children affected severe hereditary diseases (see), and in the protection of genotype P. man from the accumulation of harmful mutant genes. Cm. also, Genetics, Mutation, Evolutionary doctrine.