Producers :These are the energy transducers which convert solar energy into chemical energy with the help of inorganic and organic substances.The producers  make their own food  and are referred to as autotrophs (auto means self and troph means nourishing). Autotrophs are further of two types photoautotrophs and chemoautotrophs. Photoautotrophs mainly green plants make food through a process called photosynthesis. Chemoautotrophs, utilize energy generated in an oxidation-reduction e.g. microorganisms like sulphur bacteria.

Consumers or heterotrophic (hetero-other, trophic-nourishing) organisms are mainly animals. Depending upon the food habits consumers are classified as Herbivores, Carnivores .Herbivores eats plants. Carnivores eat animals. Carnivores are further classified as carnivore of order1 (C₁), carnivore of order 2 (C₂) and so on depending on their food habits. Omnivores eat both plants and animals.

Decomposers are also heterotrophs that depend upon dead organic matter for their food. They are also termed as saprotrophs (sapro means to decompose). They play a very important role in the ecosystem as they recycle nutrients by breaking down complex organic matter found in plant and animal body and ultimately releasing simple substances e.g. microorganisms like bacteria, fungi etc.