Which of the following is a density-dependent factor?

• A. Weather
• B. Competition
• C. Natural disasters
• D. Fire from a lightning strike

Answer: (B)

Density-dependent factors change in strength as population size changes. They become more influential when more individuals are living in the same area. Competition for limited resources like food, space, and mates fits this idea perfectly: as the population grows, resources run short, making survival and reproduction tougher, which slows growth and helps stabilize the population as it nears carrying capacity.

In contrast, factors like weather, natural disasters, or fires from lightning tend to affect populations regardless of how many individuals are present. A storm can wipe out a similar proportion of a small or a large population, so their impact does not scale with density.