Give an account on the concept of trophic level in an ecosystem.

Explanation

A trophic level refers to the position of an organism in the food chain. The number of trophic levels is equal to the number of steps in the food chain. The green plants (producers) occupying the first trophic level `(T_1)` are called producers. The energy produced by the producers is utilized by the plant eaters (herbivores) they are called primary consumers and occupies the second trophic level `(T_2)`.
  Herbivores are eaten by carnivores, which occupy the third trophic level `(T_3)`.
  They are also called secondary consumers or primary carnivores. Carnivores are eaten by the other carnivores, which occupy the fourth trophic level `(T_4)`. They are called the tertiary consumers or secondary carnivores. Some organisms which eat both plants and animals are called as omnivores (Crow). Such organisms may occupy more than one trophic level in the food chain.