What is the term for the number of individual organisms per defined unit area?

• A. Population density
• B. Dispersion
• C. Carrying capacity
• D. Species richness

Answer: (A)

Population density is the number of individual organisms per defined unit area (or volume). It tells you how crowded a population is in a given space and is useful for comparing habitats or tracking how populations change over time. This concept focuses on count per area, not how those individuals are spread out.

Dispersion describes the pattern of spacing among individuals—whether they are clumped, uniform, or random—regarding arrangement rather than overall numbers. Carrying capacity is the maximum population size that the environment can sustain indefinitely given resources, which is about limits over the long term rather than a snapshot of current counts. Species richness is about how many different species are present in an area, not how many individuals there are in total.

For example, if 60 rabbits occupy 0.2 hectares, the density is 60 / 0.2 = 300 rabbits per hectare.