Explain with the help of an example each of any three ways the ecologists use to measure the population density of different organisms rather than by calculating their absolute number.
Method to measure population density: Population density is the number of individuals of a species per unit area or volume. PD= N/S Where N = The no. of the individual in the region S = No. of the unit area in a region Number of animals per square kilometre Number of trees per hectare A number of phytoplanktons per cubic litre of water. Sometimes the relative densities also serve the purpose, that is The number of fish caught per trap is good enough to measure the population of fish. Tiger census is based on pug marks and faecal pellets.
