Trophic level is a step or division of food chain( further a part of food web) which is characterized by the method of obtaining its food.
The number of trophic levels is equal to the number of steps in the food chain.
A fundamental similarity of all trophic levels is that they use a part of food in body building while a major part of it is consumed in liberation of energy during respiration.
Organisms of one trophic level have the same food habit e.g.carnivory.
Each trophic level may have several resources.
Trophic level is a functional level. A number of species may operate at it.
A single species may occupy more than one trophic levels. Sparrow is a primary consumer if it feeds on seedsfruits and peas. But it is a secondary consumer if it feeds on insect and worms.
An ecosystem can support only a limited number of trophic levels hardly 3-5 because nearly 90% of energy is lost when one moves from one trophic level to the next one in a food chain or food web.