Correct Option
The correct option isThey convert organic waste into nutrient-rich compost.
Explanation
Vermicomposting is a biological process in which earthworms, specifically redworms (such as Eisenia fetida), are used to convert organic waste into humus-like material known as vermicompost. Ecologically, redworms function as detritivores, playing a critical role in the fragmentation and decomposition of organic matter.
Option Analysis
- They act as primary producers. is Incorrect: Primary producers are autotrophs, such as green plants and algae, capable of synthesizing their own food through photosynthesis. Redworms are heterotrophs that rely on consuming existing organic matter.
- They convert organic waste into nutrient-rich compost. is Correct: The primary role of redworms in vermicomposting is the consumption of decaying organic waste. They grind this material in their gizzards, facilitating rapid decomposition. The end product, excreted as worm castings, is rich in water-soluble nutrients and beneficial microorganisms, serving as a high-quality organic fertilizer.
- They fix atmospheric nitrogen. is Incorrect: Nitrogen fixation is the conversion of atmospheric nitrogen into ammonia, a process performed by specific prokaryotes like Rhizobium and Azotobacter. Earthworms do not fix nitrogen, although their activity may improve soil aeration, indirectly benefiting nitrogen-fixing bacteria.
- They eliminate soil bacteria. is Incorrect: Redworms do not eliminate soil bacteria. Instead, they promote microbial activity. The gut of the earthworm acts as a bioreactor, and their castings typically contain a higher load of beneficial bacteria and enzymes compared to the surrounding soil.
Key Takeaway: Redworms accelerate the nutrient cycling process by physically fragmenting organic waste and facilitating microbial decomposition, transforming waste into nutrient-rich compost.