The modes of genetic structure and size dynamics of structured population are investigated in this work. The reproductive potential and survival rate of reproductive part of population in following years of life are determined on genetic level. It has been shown that evolutional increasing of average population fitness is followed by arising of complicated dynamics of population size and of genetic structure. Further growth of fitness is capable to stabilize the genetic structure of population and so only the population size will be fluctuating with regular or chaotic circling.
