The number of individuals per unit area or volume?

• A. Population Density
• B. Population
• C. Habitat
• D. Intertidal Zone

Answer: (A)

This question is about population density—the number of individuals in a defined unit of space. Density normalizes a population to area (or volume), so you can compare how crowded different places are. It’s calculated as the total number of individuals (N) divided by the area (or volume) they occupy (for example, individuals per square meter or per cubic meter).

Understanding the other terms helps: a population is just the total count of individuals, not normalized by space. A habitat is the environment where organisms live, and the intertidal zone is a specific type of habitat, not a measurement of how crowded a population is.

So the best match for “the number of individuals per unit area or volume” is population density.