Question

How many of the following can be used to measure the population density?
1. Number of individuals
2. Age of pre-reproductive individuals
3. Relative population densities
4. Age of post-reproductive individuals

Answer 1

Population size is technically called population density (designated as N).

The most appropriate measure of population density is generally in terms of number. For example, the density could be as low as less than 10 in case of Siberian cranes that migrate to Bharatpur wetlands in any year or it can be very high and go up to millions as in case of Chlamydomonas algae in a pond.

Sometimes, when the size of the population is huge and counting becomes difficult, relative densities are taken into consideration instead of absolute population densities (absolute population densities refer to the exact number of organisms in a particular habitat). For example, the number of fish caught per trap helps us to estimate the population of fishes in the lake at a time.

Population density cannot be measured in terms of age of pre-reproductive individuals or post-reproductive individuals. Rather they are used to construct the age pyramids which help us to predict the growth status of the population.