Original sentence: Ecological niches are usually populated, but evolution of a species may enable it to overcome the difficulties encountered in an initially hostile environment.In biology, a rarely occurring situation in which a group of individuals of a species appear in a new, inhabitable area suitable for more individuals, and begin to populate it.In ecology, population control is on occasions considered to be done solely by predators, diseases and parasites, though at many times human effects on animal and plant populations are also considered.Migrations of animals may be seen as a natural way of population control, for the food on land is more abundant on some seasons.The area of the migrations' start is left to reproduce the food supply for large mass of animals next time around.This may also happen if individuals of a species have been transferred to new areas on purpose or by accident