A species or an organism can never live alone. They are always influencing each other and organizing themselves into communities, besides they have functional relationship with their external environment. This structural and functional system of communities and their environment is called ecosystem. The word ecosystem was coined by Tinsley in 1935. The ‘eco’ means environment. The central theme of ecosystem concept is that at any place where an organism lives, there is a continuous interaction between the living and the non-living components, i.e., between plants, animals and their environment. They continuously produce and exchange materials. This means, that there are mechanisms for continuous absorption of materials by organisms for the purpose of production of organic materials and their conversion back into the inorganic form, much of which is then released back into the environment. The interaction between living and non-living components of an ecosystem involves input, transfer, storage and output of energy and essential materials through the system. Each of these processes is energy-dependent. As a result of these complex interactions, the ecosystem has to adjust to these changes and attains a state of equilibrium. An ecosystem therefore, is a system that is self-regulatory based on feedback information about the population, and the limiting factors which control the living and non-living components. Before we explain, the functioning of the components of the ecosystems let us first talk about a larger unit of natural landscape biosphere.