1. Earthworms

2. Jellyfish

3. Millipedes

4. Seahorses

5. Woodlice

Select the correct answer using the code given below.

(a) 1, 2 and 4 Only

(b) 2, 3, 4 and 5 Only

(c) 1, 3 and 5 Only

(d) 1, 2, 3, 4 and 5

15. Ans: c

Explanation: 

Two groups of organisms responsible  for the decomposition of dead organic matter (detritus): bacteria and fungi are called decomposers, while animals that consume dead matter are known as detrivores.

Detritivores play a crucial role in the biogeochemical processes of soil and nutrient cycling through their consumptive and burrowing activities. In a food web nutrients are recycled in the end by decomposers. Decomposers work at every level, setting free nutrients that form an essential part of the total food web. 

Detritivores 

• A detritivore is a heterotrophic organism, which obtains its nutrition by feeding on or consuming detritus (plus any associated bacteria and fungi). Detritus is the organic matter made up of dead plant and animal material. 
• Detritivores may also obtain nutrition by coprophagy, which is a feeding strategy involving the consumption of feces.
• Detritivores are often invertebrate insects such as mites, beetles, butterflies and flies; mollusks such as slugs and snails; or soil-dwelling earthworms, millipedes and woodlice.
• Examples of detritivores in marine environments are crustaceans such as crabs and lobsters, echinoderms such as sea stars or sea cucumbers. 
• Many of these marine detritivores occupy a similar niche to terrestrial soil-dwellers, living on or within the seabed known as the benthos. These organisms are often called “bottom-feeders”. 

Millipedes are arthropods and, unlike insects, do not have three clearly defined body sections, each with a pair of legs. Millipedes are worm-like animals with numerous body segments and legs, feed on decaying plant matter and are found in moist environments, as they cannot survive long in dry conditions. 

Earthworms are important organisms in soil communities and are known for sustaining the life of the soil. They are used as a model organism in environmental risk assessment of chemicals and soil toxicology. Soil provides physical and nutritive support to the agriculture system by regulating biogeochemical cycles, nutrient cycle, waste degradation, organic matter degradation etc. 

Woodlice (also called sow bugs, pill bugs and slaters) are terrestrial isopods (class of Crustacea) which have invaded terrestrial habitats from aquatic environments. Most species can still tolerate submersion in water saturated with O2. They can remove heavy metals such as cadmium, arsenic and lead by ionising it, so preventing metal ions leaching in to groundwater.

Their diet consists mostly of decaying organic materials such as leaf litter, decayed wood, fungi, and bacterial mats. 

Hence, option c is correct.

Read: Previous Year UPSC Environment Questions (PYQs) With Explanation 2021