With reference to the food chains in ecosystems, which of the following kinds of organism is / are known as decomposer organism / organisms? 1. Virus 2. Fungi 3. Bacteria Select the correct answer using the codes given below.

Decomposers break down dead organic matter and return nutrients to the soil, closing the loop in nutrient cycling. In the standard food chain framework, the decomposers are fungi and bacteria, so statements 2 and 3 are correct. Answer: B.

Statement 1 is wrong. Viruses are not free-living organisms. They are obligate intracellular parasites that need a living host cell to replicate. They do not feed on dead matter or release nutrients from it, so they are not counted among decomposers.

Statement 2 is right. Fungi, such as moulds and mushrooms, secrete extracellular enzymes that digest dead wood, leaf litter and other complex organic compounds, then absorb the products.

Statement 3 is right. Bacteria, including saprophytic soil species, carry out ammonification and related steps that mineralise organic nitrogen and phosphorus, making them available to plants again.

Core concept: decomposition and nutrient recycling. This links to the ecosystem and biogeochemical cycle topics in Environment and to Mains GS3 questions on soil health and waste management.

Trap: aspirants pick option D because viruses are often grouped with microbes in biology. Remember the functional definition: decomposers are saprotrophs that live on dead matter, and viruses do not qualify.