Definition: Given a scientific passage and an answer, generate a question for the given answer.
Input: Passage: Population density is the average number of individuals in a population per unit of area or volume. For example, a population of 100 insects that live in an area of 100 square meters has a density of 1 insect per square meter. If the same population lives in an area of only 1 square meter, what is its density? Which population is more crowded? How might crowding affect the health of a population?. Answer: population density
Output:
What is the term for the average number of individuals in a population per unit of area or volume?