What is carrying capacity in population ecology?

• A. The average number of individuals in a population over time
• B. The rate of immigration into a population
• C. The genetic diversity of a population
• D. The maximum population size that an environment can sustain indefinitely given resource limits

Answer: (D)

Carrying capacity is the maximum population size an environment can sustain indefinitely given resource limits. This concept reflects that finite resources such as food, water, space, and shelter cap how large a population can remain over the long term. As numbers rise and resources become scarcer, growth slows due to density-dependent factors like competition, disease, and predation, until births and deaths balance and the population stabilizes around this limit. It’s not simply an average population over time, nor a rate of immigration, nor the genetic diversity of the population. The correct idea is that the environment constrains long-term population size to a finite level defined by available resources, and that level can shift if resource conditions change.