All food chains begin with producers, except -

The correct answer is Option (1) → Detritus food chain

An ecosystem has two kinds of food chains. The grazing food chain (GFC) starts with producers, the green plants, which are eaten by herbivores and then by carnivores. The detritus food chain (DFC) starts from dead remains instead.

Option (1) Detritus food chain — Does not begin with producers. Its first link is detritus, the dead organic matter of plants and animals. Decomposers feed on it, and the chain goes on from them.

Option (2) Terrestrial food chain — Begins with producers. On land the grazing chain starts with green plants, as in grass → goat → man. A land ecosystem also has detritus chains, but a food chain named only by its habitat is the grazing type.

Option (3) Aquatic food chain — Begins with producers. In water the chain starts with phytoplankton, the tiny green producers. In an aquatic ecosystem the grazing food chain is the major path of energy flow.

Option (4) Food web — Begins with producers. A food web is not one chain but a network of food chains linked to one another. Its grazing chains still begin with the producers, which capture the sun’s energy for the whole web.

NCERT Extract:
Energy Flow –