A density-dependent factor is a factor that affects the size or growth of a population of living things in response to the density of the population. These factors are biotic in nature and often arise from biological phenomena, such as disease, competition, and predation, rather than from physical and chemical phenomena/45%3A_Population_and_Community_Ecology/45.02%3A_Environmental_Limits_to_Population_Growth/45.2C%3A_Density-Dependent_and_Density-Independent_Population_Regulation). Density-dependent factors are sometimes called regulating factors because of their potential for maintaining population density within a narrow range of values. As the density of a population increases, the effects of density-dependent factors become more pronounced, leading to a decrease in the populations per capita growth rate. Some common examples of density-dependent factors include:
- Competition within the population for resources such as food, water, shelter, mates, and light/45%3A_Population_and_Community_Ecology/45.02%3A_Environmental_Limits_to_Population_Growth/45.2C%3A_Density-Dependent_and_Density-Independent_Population_Regulation).
- Disease, which can spread more easily in populations where individuals live in close proximity with one another/45%3A_Population_and_Community_Ecology/45.02%3A_Environmental_Limits_to_Population_Growth/45.2C%3A_Density-Dependent_and_Density-Independent_Population_Regulation).
- Predation, which can increase as the density of prey populations increases/45%3A_Population_and_Community_Ecology/45.02%3A_Environmental_Limits_to_Population_Growth/45.2C%3A_Density-Dependent_and_Density-Independent_Population_Regulation).
Density-dependent factors can lead to a logistic pattern of growth, in which a populations size levels off at an environmentally determined maximum called the carrying capacity. The dynamics of most populations of living things are influenced by a combination of density-dependent factors and density-independent factors, and the relative effects of the factors vary among populations.
