INTRODUCTION E cosystem is formed by biotic and abiotic factors and their interactions with each other each factor plays very important role in the ecosystem. Producers like plants are important. Herbivores like deer, goats, sheep, cattle horses, camels, etc. feeding upon producers are also important. Predators like lion and tiger which prevent over population of herbivores are equally important. The caterpillars found in nature, organisms present in filthy places, termites, insects present in dung. These organisms are also important though they are dirty. They are responsible for cleaning the environment. Our existence is due to these factors present around us. DEFINITION FOOD CHAIN : Food chain is a linear sequence of organism which starts from producers' organisms and ends with decomposer species. It shows the flow of energy from one organism to the other. FOOD WEB : Food web is a connection of multiple food chains. Food chain and food web are integral part o...