PopulationYou must be familiar with the term 'population'. It is one of the most talked about issues of this century. It is feared that the rapid growth of the world population if allowed to continue, might outstrip the food supply in the near future. The present high rate of population growth is a major concern of the governments, scientists and administrators. Have you ever wondered as to what is meant by population?In a technical sense 'population' is defured as a group of freely interbreeding the same species present in a specific area at a given time. For example, when we say thatindividuals of the population of a city is 50,000, we mean that there are 50,000 individuals of Homo sapiens in that town. Other living organisms, for example cats and dogs present in the city are not included as they are populations of two different species.In nature, population of a species is subdivided into a number of local breeding populations called deme. Demes are geographically separated populations of the same species. For example, the garden lizards of Qutub Minar. Delhi, form a separate deme from the garden lizard of Lodi Gardens, Delhi or the garden lizards of Swaraj Bhawan, Allahabad. Consequently, in a deme each individual has an equal opportunity of mating with another individual of the opposite sex, but not with individuals in another deme. Because of frequent mating and similar environmental conditions members of a deme resemble each other more closely.A population exhibits certain characteristics which can only be expressed at the population level and not shared by the individuals of the population. For example, individual organisms are born, grow and die but characteristics such as birth rate, death rate, density are only meaningful at the population level.