Final answer:
Population density is calculated by dividing the total number of individuals in a population by the area or volume they occupy, which represents the population size per unit area or volume of the habitat. This value informs us how crowded a population is. Quadrat sampling is a common method used to estimate these values for populations in the field.
Step-by-step explanation:
Mathematically, the total population in population size per unit area or volume of the habitat is known as population density. Population density is calculated by dividing the population size (N), which is the total number of individuals, by the area or volume they occupy. This measure provides insight into how crowded a population is and can indicate the health of the population as well as potential challenges in finding a mate and competition for resources.
For example, if a population of 100 insects lives in a habitat of 100 square meters, the population density is 1 insect per square meter. If the same population lives in just 1 square meter, the density would significantly increase to 100 insects per square meter, indicating a more crowded situation which can impact the health and behaviors of the population.
To estimate population size and density in the field, scientists may use the method of quadrat sampling. A quadrat is a square marked on the ground where researchers count the number of individuals within. By sampling various quadrats throughout the habitat and extrapolating this data, an estimate of the overall population size and density is obtained. This is especially useful for immobile or slow-moving organisms where direct counting is not feasible.