In only the autotrophs can produce their own food and the others are dependent on this production. All the living organisms in an ecosystem are interrelated in terms of feeding and being fed thus forming a definite chain known as food-chain. Food chains are of two main types:
1. Grazing food-chain: Starting with autotrophic plants and end in consumers. Eg. Sun-Grass-Deer-Tiger-Decomposer.
2. Detritus food-chain: Starting with organic and decomposed animal or plant parts and containing different Bacteria, Fungi and other detritivores. These food-chains are common in all ecosystem.
In addition to these, there are some secondary food-chains. E.g. Parasitic food-chain, made of host, Parasites and other microorganisms.