Type I curves flat during early and middle life and drops suddenly as death rates increase among the older individuals. Type II curves are intermediate with mortality being more constant over the life span. Type III curves show very high death rates for the young followed by lower death rates after the individuals have survived to a certain critical age. Increasing population size reduces available resources limiting population growth. In restricting population growth, a density-dependent factor intensifies as the population size increases, affecting each individual more strongly.
Population growth declines because of death rate increase, birth rate decrease or both.
There is a reduction in the food supply which restricts reproduction resulting in less offspring. The competition for space to establish territories is a behavioral mechanism that may restrict population growth. Predators concentrate in areas where there is a high concentration of prey. As long as the natural resources are available, in sufficient quantity, the population will remain constant. As the population decreases so do the predators.