Food Chain and Food Webs

"Food chain is a series of groups of organisms called trophic levels, in which, there is repeated eating and eaten by so as to transfer food energy".

Or

"The series of populations or organisms of an ecosystem through which food and energy contained in it passes with each member becoming the food of the later is called a food chain".

For e.g.,

a) Food chain observed in a river:

b) Food chain observed in a pasture:

The transfer of food energy from plant sources through a series of organisms forms a 'food chain'.

The base of the food chain is always formed by a plant (producer / autotroph), which is grazed on by a herbivore, which is predated over by a carnivore, which may be eaten by another carnivore.

A food chain, can therefore, be represented as,

where each link represents a trophic level.