Populations in a periodically changing habitat. Comparison of two extended models

We investigate the dynamics of a population in periodically changing external conditions and we determine the survival chance as a function of the selection pressure and changeability. We compare two extended models. In one, an individual is characterized by its genetic structure from which a phenotype follows, while in the second model, an individual is described by a real number directly representing the phenotype. We show that although the models exhibit in general similar behavior, the simpler model could in some special conditions, give incorrect results