Which type of limiting factor is often biotic and density-dependent (examples include predation, disease, parasites, and competition)?

• A. Biotic factors
• B. Density-independent factors
• C. Density-dependent factors
• D. Abiotic factors

Answer: (C)

Density-dependent factors are limiting factors whose impact increases with population size, often arising from biotic interactions. When more individuals are present, encounters between predators and prey, spread of disease, parasite transmission, and competition for limited resources all rise, so the limiting effect grows as the population grows. This contrasts with density-independent factors, like weather or natural disasters, which affect individuals regardless of how many are in the population. Abiotic refers to non-living factors, while biotic factors involve living organisms. Since predation, disease, parasites, and competition are all biological interactions whose influence scales with density, they exemplify density-dependent factors.