What is the primary role of decomposers in the ecosystem?

The correct answer is Option (2) → To break down dead organic matter into simple inorganic materials

Decomposers are heterotrophic organisms, mainly fungi and bacteria. They secrete digestive enzymes that break down dead and waste materials into simple, inorganic materials, which they then absorb. In this way the nutrients locked in dead bodies go back for reuse.

Option (1) To capture sunlight for photosynthesis — Incorrect. Capturing sunlight for photosynthesis is the work of the producers (green plants and photosynthetic bacteria), not of decomposers.

Option (2) To break down dead organic matter into simple inorganic materials — Correct. Decomposers break down complex organic matter of dead remains into inorganic substances like carbon dioxide, water and nutrients. This process is called decomposition.

Option (3) To prey on other organisms — Incorrect. Feeding on other living animals is the way of life of predators and carnivores. Decomposers get their food from dead organic matter.

Option (4) To convert carbon dioxide into oxygen — Incorrect. Changing carbon dioxide into oxygen is linked to photosynthesis in green plants. Decomposers, in fact, release carbon dioxide when they break down detritus.

NCERT Extract:
Decomposition – “You may have heard of the earthworm being referred to as the farmer’s ‘friend’. This is so because they help in the breakdown of complex organic matter as well as in loosening of the soil. Similarly, decomposers break down complex organic matter into inorganic substances like carbon dioxide, water and nutrients and the process is called decomposition.”
Energy Flow – “… Decomposers secrete digestive enzymes that breakdown dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them.”