Question

An organism that eats organic matter and returns nutrients to the soil is called as a
A) Primary consumer
B) Secondary consumer
C) Scavenger
D) Decomposer
E) Producer

Answer 1

Hint:In an ecosystem one organism eats another which is consumed by another. A linear chain of transfer of energy from producers to consumers and decomposers is called a food chain.

Complete answer:
To answer this question, we must know about the tropic levels in a food chain.
Each level in a food chain is called trophic level. Each trophic level consist of:

i) Producer- It forms the base of the food pyramid. It has the maximum energy. It consists of the photosynthetic autotrophs which can prepare their own food.
ii) Primary and secondary consumers- The primary consumers are the organisms which feed on producers. The secondary consumers feed on primary consumers like deer.
iii) Scavengers- They are the organisms that consume dead organisms. Example crow.
iv) Decomposers—These organisms feed on dead and decaying matter and obtain their nutrients from them. They decompose the organic matter back to the soil. Example microorganisms.

Thus the correct answer is (D). An organism that eats organic matter and returns nutrients to the soil is called a Decomposer.

Note:The decomposers decompose the dead organic matter and recycle the nutrients back to the soil. Some insects, worms, and fungi act as excellent decomposers. These organisms live on the top layer of the soil. The decomposers convert the waste to manure and fertiliser which are rich in nitrogen and carbon. This makes the soil fertile.