Which of the following best describes a density-dependent factor?

A density-dependent factor is one that affects a population's growth and reproduction in relation to the population density. Food availability is a prime example of this concept because as the population of a species increases, the competition for food resources intensifies. When there are more individuals in a population, the demand for food rises, which can lead to a decrease in health, reproductive rates, and overall survival if the food supply cannot meet the increased demand. Conversely, if the population is smaller, there is often less competition for food, allowing more individuals to thrive.

In contrast, the other options—weather conditions, natural disasters, and climate change—represent density-independent factors. These factors can affect populations regardless of their density. For instance, a drought (a weather condition) can limit food availability but does not depend on how many individuals are in a population. Similarly, natural disasters like hurricanes can wipe out populations regardless of their size or density. Climate change can lead to shifts in habitat or resource availability as well but applies to populations indiscriminately based on their numbers. This distinction emphasizes why food availability is categorized as a density-dependent factor rather than the others, which do not depend on population density for their effects.