(i) What is population density ? Why are ecologists interested in measuring it ?
(ii) Write the different ways of measuring population density.Explain any two with the help of specific examples.

Explanation

Ecologists are interested in measuring population density for the following reasons :
1. The size of the population tells us a lot about its status in the habitat.
2. Ecological processes such as outcome of compettion with another species, the impact of a predator or the effect of pesticide application can be easily can be easily evaluated in terms of change in the population size.
(ii) Population density means number of individuals present per unit area, population density can be measured by determining the population size.The different methods to study population size are as follows ,
(1) Per cent cover or biomass : In an area with 200 parthernium plants and only one banyan tree with large conopy, the density of banyan tree is small but does not reflect its important role in the community. Here percent cover or biomass is a more meaningful method of assessing population density.
(2). Total Number : It involves the counting of organisms in the given area.
(3) Relative Density : In this method, there is no need to count the organisms individully. Example the number of fishes caught per trap gives the measure of their total density in a given water body.
(4) Indirect Assessment : The tiger census is based on pug marks and faecal pellets.