Define food chain and food web.

As the living organisms depend on each other for their food and energy requirements, they form a chain like arrangement of trophic levels that shows the flow of energy from consumers to producers at different levels. This arrangement is called food chain. A food chain includes organisms from one ecosystem only.

The individual organisms from one ecosystem also depend on organisms from other ecosystems for food and energy interaction. This creates linking of food chains to form a network, called the Food web.