The unique treatise of Yuri P. Altukhov is based on several decades of research on natural communities, modelling them in experiments and with computer analysis. Essential features of species population structure, such as genetic population subdivision, hierarchical systemic organization, unrandom structure of gene migration, as well as factors and conditions of genetic stability of populations are revealed. Elucidating principles of stabilization of gene pools of agricultural animals and plants, the author discusses a strategy of conservation and sustainable management of natural gene pool resources. He considers the specificity of genetic processes in modern human populations and presents a new view on genetic mechanisms of speciation. New evidence is given for the adaptive value of molecular polymorphism in populations. The hypothesis of optimal genetic diversity of populations as the most important condition of their stable reproduction in generations and the principles of rational interaction of human with nature are treated in detail.