(A) Birth rate = No. of individuals born/Total no. of individuals `=40//200=0.5` frogs per year.
(b) Populatio 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 fallows :
(1) Per cent conver or biomass : In an area with 200 parthenium plants and only one banyan tree with large canopy, the density of banyan tree is small but does not reflect its important role in the community. Here, precent 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 count the organisms individuall. 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.
