Question

An organism living on dead and decaying organic matter.

Answer 1

Decomposers are organisms that break down dead or decaying organisms, and in doing so, they carry out the natural process of decompositions like herbivores and predators, decomposers are hetero trophic, meaning that they use organic subtrates to get their energy, carbon and nutrients for growth and development. 

Answer 2

An organism that lives on living or dead and decaying organic matter is called a parasite. Some examples are lice, tapeworms, fungi and some decomposing bacteria...

Hope it is helpful... ^_^