Final answer:
Density-dependent factors, such as competition, predation, and disease, increase in effect with higher population density and are central to regulating population growth and maintaining ecosystem stability.
Step-by-step explanation:
Density-dependent factors are biotic factors in the environment that have an increasing effect on population size or growth rate as population density increases. These factors include predation, inter- and intraspecific competition, accumulation of waste, and diseases such as those caused by parasites. As a population becomes denser, resources become more limited, and the organisms may compete more for these resources, leading to increased mortality or reduced reproduction rates.
Density-dependent regulation is crucial in preventing overpopulation and maintaining ecosystem stability. For example, if a prey species becomes too abundant, predators may find it easier to hunt, thus increasing predation rates and controlling the prey population. Conversely, if prey is scarce, predator numbers may decline due to starvation. Another example is disease spreading more quickly in densely populated areas, which can significantly affect mortality rates.