Question 26 from UPSC CSE 2021 - Environment

Question

Which of the following are detritivores?
1. Earthworms
2. Jellyfish
3. Millipedes
4. Seahorses
5. Woodlice
Select the correct answer using the code given below.

IASCODEX · Accepted Answer

Correct Option: C. 1, 3, and 5 only

Strategy: Identify the ecological role of a detritivore. Select organisms that consume decomposing matter (earthworms, millipedes, woodlice) and eliminate those that are predators (jellyfish, seahorses).

Key Info: Detritivores are organisms that obtain energy by feeding on detritus—dead and decomposing organic matter—and play a vital part in decomposition and nutrient recycling within ecosystems.

**Common Detritivores**
- **Earthworms** (phylum Annelida) actively ingest soil and decaying leaves, breaking down organic matter and enhancing soil fertility.
- **Millipedes** (class Diplopoda) feed on decaying plant material, contributing to litter decomposition.
- **Woodlice** (order Isopoda) are crustaceans that consume rotting wood and leaf litter.

**Non-Detritivores for Comparison**
- **Jellyfish** (phylum Cnidaria) are aquatic, predatory animals feeding on plankton, fish larvae, and sometimes other small marine animals. They are not involved in decomposing organic matter.
- **Seahorses** (genus Hippocampus), fish belonging to the family Syngnathidae, feed primarily on small crustaceans like shrimp or copepods. They capture live, moving prey and are secondary consumers in marine food chains, not detritivores.

Detritivores differ from decomposers (such as fungi and bacteria) in that they physically ingest detritus rather than enzymatically digesting it externally. Their action accelerates decomposition processes and nutrient return to the soil. In contrast, jellyfish and seahorses occupy consumer roles, making them ecologically distinct from detritivores.

IASCODEX · Answer

Option A: 1, 2, and 4 only

IASCODEX · Answer

Option B: 2, 3, 4, and 5 only

IASCODEX · Answer

Option D: 1, 2, 3, 4, and 5

Which of the following are detritivores? Earthworms Jellyfish Millipedes Seahorses Woodlice Select the correct answer using the code given below.

Which of the following are detritivores?

Earthworms

Jellyfish

Millipedes

Seahorses

Woodlice
Select the correct answer using the code given below.