A food chain demonstrates the flow of food energy in an ecosystem. It is based on the tropics levels which normally refer to the functions of organisms with regard to energy flow. Many food chains exist in an ecosystem, but as a matter of fact these food chains are not independent. The marsh plants are eaten by variety of insects, birds, animals, mammals and fishes and some of the animals are eaten up by several predators. Similarly in the food chain-Grass – Mouse – Snake-Owls. Sometimes mice-are not eaten by snakes but directly by owls. This types of food chain are become inter linked.