Which statement defines carrying capacity?

• A. A fixed number that never changes.
• B. The year in which population reaches peak size.
• C. The number of individuals that can migrate into an area each year.
• D. The maximum population size the environment can sustain indefinitely.

Answer: (D)

Carrying capacity is the maximum population size that the environment can sustain indefinitely, given the available resources such as food, water, space, and other ecological factors. It represents the long-term limit where the environment can balance births and deaths (and immigration vs. emigration) without degrading the resources. This limit isn’t fixed; changing resources, climate, technology, or ecosystem conditions can raise or lower it. It’s not about a specific year when the population peaks, nor about how many individuals can migrate into an area each year. Those are different ideas.