In population ecology, what does population density mean?

• A. The proportion of individuals entering or leaving a population through migration per unit time
• B. The rate at which individuals are added to a population through reproduction per unit time
• C. The total number of individuals of a species in an entire geographic range
• D. The number of individuals of a species per unit area or volume at a given time

Answer: (D)

Verified step by step guidance

1. Understand that population density refers to how many individuals of a species are found in a specific area or volume at a particular time.
2. Recognize that population density is different from total population size, which counts all individuals across the entire geographic range without considering area or volume.
3. Note that population density is a measure of concentration, often expressed as the number of individuals per unit area (e.g., per square kilometer) or per unit volume (e.g., per cubic meter).
4. Distinguish population density from rates of change such as migration (individuals entering or leaving) or reproduction (birth rate), which describe dynamics rather than static counts.
5. Summarize that population density provides insight into how crowded or sparse a population is in a given habitat, which can affect interactions like competition, predation, and resource availability.