Practice question

Drought originates from an abiotic shortage of precipitation and generally affects a population regardless of whether that population is sparse or crowded. Disease transmission, competition, and many predator responses usually strengthen with density because individuals encounter one another or shared resources more often. The distinction concerns how impact changes with density, not whether the factor is biotic or abiotic in every possible case. Population regulation concerns feedback, not mere limitation. A drought may sharply reduce numbers yet fail to push the population toward a repeatable equilibrium. Competition, disease, territoriality, and some predator responses can strengthen with crowding, changing births or deaths in a direction that opposes the density change and thereby producing regulation. The example should therefore be understood as an application of a general model, with its assumptions kept explicit. Ecological predictions remain conditional on the stated environment, because changing resources, mortality, or interactions can alter the observed demographic pattern.