What is a food chain? 

Explanation

(i) Food chain is a linkage of organisms within an ecosystem, in which each link feeds on the one before it and is fed on by the one after it.
(ii) Only the first link in the chain is a producer and all the rest are consumers.
(iii) In the ecosystem, the energy is transferred from on organism to another with food, in a definite sequence.
(iv) Initially, solar energy is absorbed by producers and with the help of photosynthesis the food is synthesized.
(v) Energy gets transferred from producers to consumers of different levels.
(vi) Decomposers derive energy form dead organisms by decomposition from all levels.
(vii) The flow of energy is unidirectional.