Waves of Life

fluctuations in the number of individuals in a population. The term was introduced by the Russian biologist S. S. Chetverikov in 1915. The fluctuations may be seasonal or nonseasonal, recurring at various intervals. They usually increase in length as the cycle of development of the organisms becomes longer. Waves of life are often accompanied by fluctuations in the range of the population.

Chetverikov treated the evolutionary role of waves of life as a factor capable of altering the direction and intensity of selection, as well as the concentration of genes present in the population. The term was later replaced by the concept of“population waves” (one of four elementary evolutionary factors—the mutation process, population waves, isolation, and natural selection). The main significance of waves of life reduces to the random changes in the concentrations— particularly low concentrations—of various mutations and genotypes present in populations and to a weakening of the pressure of selection by an increase in the number of individuals in the population and its strengthening by a decrease in their number. The term“waves of life” is also taken by some—among them the Soviet geologist B. L. Lichkov—to mean stages in the development of the plant and animal worlds roughly corresponding to the succession of geological cycles.