In Ecology, certain factors that affect the size of a population can either be dependent on size or not. Density-dependent factors are those factors that affect population of organisms in dependence of how dense the population is. Examples of these density dependent factors are diseases, predation etc.
For example, a certain disease will spread faster among a population of organisms whose size is dense but slower in a scarcely densed population. Hence, disease as a factor is dependent on population size. Note that; Drought, Climate, and Natural Disasters will wipe out a population irrespective of its size.
