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How do density-dependent factors regulate population size?
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Graph of the world's estimated human population from 1700 until 2000, with population projections extending until 2100.
Density-dependent factors regulate population size by exerting effects that change in response to the number of individuals per unit area, often acting as a feedback mechanism to keep population density within a specific range.1
These factors typically arise from biological interactions rather than physical or chemical ones. As a population becomes more crowded, the following processes intensify:
- Competition: Increased demand for limited resourcesāsuch as food, water, and nesting sitesāmeans that a larger proportion of the population faces scarcity, which can lower survival and reproductive rates.12
- Disease Transmission: Infectious diseases spread more rapidly in high-density populations because individuals come into contact with one another more frequently.12
- Predation: High concentrations of prey can attract more predators, leading to increased mortality rates.2
Conversely, as population density decreases due to mortality or migration, the intensity of these factors subsides, allowing the population to stabilize. These dynamics are often represented by a logistic growth curve, where growth plateaus as the population reaches the environment's carrying capacity.12