Risk of population extinction from periodic and abrupt changes of environment

A simulation model of a population having internal (genetic) structure is presented. The population is subject to selection pressure coming from the environment which is the same in the whole system but changes in time. Reproduction has a sexual character with recombination and mutation. Two cases are considered — oscillatory changes of the environment and abrupt ones (catastrophes). We show how the survival chance of a population depends on the maximum allowed size of the population, the length of the genotypes characterizing individuals, selection pressure and the characteristics of the “climate” changes, either their period of oscillations or the scale of the abrupt shift.