Generation carryover of a fraction of population members as an animal adaptation to unstable environmental conditions

Summary A heterogeneous life cycle of individuals in a population was examined on its adaptive significance to an unstable environmental condition. The trend of population growth was simulated by a simple mathematical model in which a part of population in a certain generation was carried over to the next generation without participating in the reproduction. With the increase of the rate of carryover of individuals to the next generation the population fluctuation tended to be stabilized. A minute fraction of population is carried over, the effect is very large to prevent the population decline at a sequence of adverse environmental conditions. The population level increased greatly depending upon the extent of environmental change as far as the rate of carryover took an intermediate value. The optimum proportion of members to be carried over to the next generation was determined by the extent of environmental change and its frequency of occurrence.