What term refers to the maximum population size that an ecosystem can sustain indefinitely?

• A. Exponential growth
• B. Plateau
• C. Death rate
• D. Carrying capacity

Answer: (D)

This question tests understanding of carrying capacity, the maximum population size an ecosystem can sustain indefinitely given resources and environmental constraints. Carrying capacity arises from limited resources such as food, water, space, and the interactions among organisms (competition, predation, disease, waste accumulation). As a population grows, these factors become more limiting, causing birth rates to decline or death rates to rise, and the population tends to stabilize around this limit. If the population temporarily exceeds carrying capacity, resource shortages lead to increased mortality or emigration until levels settle back near the limit. Exponential growth describes unchecked, rapid increases that can’t be sustained long-term; a plateau describes a leveling-off in observed data but isn’t, by itself, the defining term; the death rate is just one component that can influence the approach to carrying capacity but does not specify the environmental limit.