In introductory population ecology, which formula correctly defines population density (D) for a population distributed over an area?

• A. $D=N\times A$
• B. $D=N+A$
• C. $D=\frac{N}{A}$, where $N$ is the number of individuals and $A$ is the area
• D. $D=\frac{A}{N}$, where $A$ is the area and $N$ is the number of individuals

Answer: (C)

Verified step by step guidance

1. Understand that population density (D) measures how many individuals (N) of a species are found per unit area (A). It quantifies how crowded or spread out a population is in a given space.
2. Recall that to find density, you divide the total number of individuals by the total area they occupy, because density is essentially 'individuals per area'.
3. Write the formula for population density as \(D = \frac{N}{A}\), where \(N\) is the number of individuals and \(A\) is the area over which they are distributed.
4. Note that multiplying \(N\) by \(A\) or adding \(N\) and \(A\) does not make sense for density, since these operations do not represent individuals per unit area.
5. Therefore, the correct formula for population density is the ratio of individuals to area, expressed as \(D = \frac{N}{A}\).