The correct option is (a).
Explanation
Decomposers are organisms, primarily micro-organisms, that break down complex organic matter from dead plants and animals into simpler inorganic substances. This process is essential for nutrient cycling in the ecosystem.
Statement 1 is Correct:
Decomposers are predominantly micro-organisms, such as bacteria and fungi, that inhabit the soil. They secrete digestive enzymes to break down dead organic material externally and absorb the resulting nutrients.
Statement 2 is Incorrect:
Decomposers do not feed on living plant tissues; organisms that feed on living plants are herbivores or parasites. Decomposers are saprotrophs that feed exclusively on dead and decaying organic matter (detritus).
Statement 3 is Incorrect:
The decomposition of dead organic matter results in the formation of a dark-colored, amorphous substance called humus, not sand. Humus is highly resistant to microbial action and serves as a reservoir of nutrients. Sand is an inorganic product formed through the physical and chemical weathering of rocks.
Key Takeaway:
Decomposers (bacteria and fungi) break down dead organic matter into humus and inorganic nutrients, facilitating the recycling of minerals in the ecosystem.