Define Decomposers

(a) define decomposers. Name one decomposer. (b) what is the role of decomposers in the ecosystem ?

Answers:

(a) The micro-organisms which break down the complex organic compounds present in dead organisms like dead plants and animals and their products like faeces, urine, etc., into simpler substances are called decomposers. 
Example – Bacteria and Fungi.
(b) The decomposers help in decomposing the dead bodies of plants and animals, and hence act as cleansing agents of environment.