Ecosystem is the self regulatory and self sustaining structural and functional unit of landscape (biosphere) consisting of community of living beings and the physical environment both interacting and exchanging materials between them. Food web (ie, network of food chains which becomes interconnected at various trophic levels) is meant for increasing the stability of an ecosystem by providing alternate sources of food. Primary productivity is the amount of energy accumulation in green plants through the process of photosynthesis. It is of two types ie, gross primary productivity (total organic matter synthesized by producers) and net primary productivity (weight of organic matter stored by producers).