What are decomposer ? What will be the consequence of their absence in an ecosystem ?

Explanation

Organisms which breakdown the complex organic compounds present in dead and decaying matter are called decomposers. E.g., certain bacteria and fungi. Decomposers acts as cleaning agents of environment by decomposing the dead bodies of plants and animals. They also help in recycling of materials, replenishment of soil's nutrients etc.
The consequence of their absence in an ecosystem can be idsastrous as discussed below
(i) The dead bodies would keep lying, it would never be returned to the environment.
As a result, all the nutrients pressent in soil, air and water would soon exhausted and the whole life cycly of organisms will disrupted.