(b) : Trophic level is a step or division of food chain which is characterized by the method of obtaining its food. The two fundamental trophic levels are producers and consumers. Producers belong to the first trophic level. In a lake the producers are mainly some rooted or floating plants and phytoplanktons. Primary consumers form the second trophic level. They feed on living plants or plant parts. The primary consumers are zooplanktons.