The number of individuals of a species per unit area of the habitat can be best described as

Step 1: Analyze the question The question asks for the term describing the number of individuals of a species per unit area of a habitat. The key phrase is "per unit area", which means the count is being related to a measured space.

Step 2: Explain the concepts

• Distribution: how individuals are spread out in the habitat (random, uniform, clumped). It says nothing about how many there are per unit area.
• Frequency: how often a species occurs in a set of sampling units (quadrats), usually given as a percentage of quadrats in which it appears.
• Percentage cover: the proportion of ground covered by a species, usually used for plants.
• Population size: the total number of individuals in a population. It does not include area.
• Population density: the number of individuals per unit area (or volume).

Step 3: Solution Population density = Number of individuals ÷ Area occupied

For example, if 200 grasshoppers are counted in a 50 m² field, the population density is 200 ÷ 50 = 4 grasshoppers per m².

Only population density includes both the number of individuals and the unit area, so it matches the definition in the question.

Step 4: Answer The correct option is E. Population density.

Tip: Think of "density" as being like "per". Density always has a "per unit" attached, as in people per km² or individuals per m². If the question mentions "per unit area", the answer is density. If it only asks for the total count, the answer is population size.