Which factor is density-independent?

• A. Droughts
• B. Storms
• C. Competition for resources
• D. Disease transmission

Answer: (D)

Density-independent factors affect a population regardless of how many individuals are present. Abiotic disturbances like droughts or storms fit this, because they can alter survival or reproduction no matter the population size. In contrast, factors that depend on how crowded a population is—such as competition for resources or disease transmission—change their impact with density. As populations become more crowded, resources become scarcer and contact between individuals increases, raising the potential for disease spread. So the density-independent factor among these is droughts or storms, while disease transmission is typically density-dependent because it hinges on how many individuals are in close contact.