Sunlight is the source of all energy of the earth. All the living beings are dependent upon this green plants are the producer of the ecosystem. All plants and animals of it are interconnected serially. Consequently, there develops a food chain among these. The transfer of food energy takes place from producers through a series of food levels. This is called food chain of food in the ecosystem. There are numerous food chains in an ecosystem. Food chain does not work in isolation. These are linked together to form a food web.