As a country becomes industrialized, r may remain high through the demographic transition. Only ZPG can avert global overpopulation. Populations have limited distributions. Within their range, most organisms are clumped together. A population is a set of individuals of the same species inhabiting one geographic area.
Most species have methods to avoid inbreeding.
Genetic drift, founder effect, and population bottlenecks can reduce the diversity and makeup of a gene pool. Resource limits and density-dependent factors determine the upper limit for population growth. The number of individuals in natural populations varies. The flow of energy drives ecological processes. Nature selects the individuals who use their limited energy supplies most efficiently for survival and reproduction.