The feeding of one organism upon another in a sequence another in a sequence of food transfer is known as a food chain. Another definition is “the chain of energy” (which tropically comes forms the Sun ) from one organism to another. A simple food chain is like the following Grass> Insect> Frogs> Snake> Hawk. In the food chain, the grass is the primary producer. The insects are the primary. The insects are the primary consumers because they depend upon grass for food. The frog is the primary consumer because it eats insects. The snake a secondary carnivore, eats the frog. The hawk is the tertiary carnivore, the snake. The hawk eventually dies and its remains are broken down by decay-causing bacteria and fungi. Except in deep-sea hydrothermal ecosystems, all food chain starts with photosynthesis and will end with decay.
Networks of food chains or feeding relationships by which energy and nutrients are passed in from one species of a living organism to another are called food web. A food web is represented by a graphical description of feeding relationships among species in an ecological community, e.g., of who eats whom. It is also a means of showing energy and materials (e.g., carbon) Flow through a community of species as a result of these feeding relationships.