Which of the following is an example of a density-independent factor?

• A. Forest fire
• B. Predation
• C. Disease
• D. Competition

Answer: (A)

Density-independent factors change population size regardless of how crowded the population is. They are typically abiotic or random events that affect all individuals similarly, so the impact per individual doesn’t depend on how many are present. A forest fire fits this idea well because it can kill trees and alter habitat whether there are few or many trees, and its overall effect doesn’t scale with population density. In contrast, predation, disease, and competition tend to be density-dependent because their effects rise as how many individuals are in the population increases—more prey leads to more encounters with predators, more individuals can spread disease, and more competition arises when resources are limited. So the forest fire is the best example of a density-independent factor.