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.
Contents12
- A1, 2 and 4 only
- B2, 3, 4 and 5 only
- C1, 3 and 5 only
- D1, 2, 3, 4 and 5
Show answer
Answer: (C) 1, 3 and 5 only
Detritivores feed on dead and decaying organic matter (detritus), playing a key role in decomposition and nutrient recycling.
Earthworms (Option 1) — classic detritivores that break down decaying plant material.
Jellyfish (Option 2) — carnivorous secondary consumers, not detritivores.
Millipedes (Option 3) — feed on decaying leaves and plant matter on forest floors.
Seahorses (Option 4) — secondary consumers that eat tiny shrimp and plankton.
Woodlice (Option 5) — feed on decaying wood and leaf litter.
Options 1, 3, and 5 are correct.
Answer: (c).
Detritivores like earthworms, millipedes, and woodlice are essential for breaking down dead organic matter and recycling nutrients back into ecosystems.
UPSC tests the difference between detritivores (decomposers) and consumers - jellyfish and seahorses are carnivorous consumers that eat living prey, not dead matter.
Detritivores & Decomposers
Environment detritivores decaying organic matter detritus
Detritivores & Decomposers: Role in Ecosystem Nutrient Cycling
Detritivores feed on dead and decaying organic matter (detritus)
Key examples: earthworms, millipedes, woodlice — all break down plant litter
Different from carnivores like jellyfish and seahorses that eat living prey
Essential for nutrient recycling and ecosystem health
Detritivores are organisms that feed on detritus — dead and decaying organic matter like fallen leaves, dead wood, and plant litter. They play a crucial role in breaking down complex organic materials and recycling nutrients back into the ecosystem.
Organisms from the Question
Organism | Feeding Type | What They Eat | Detritivore? |
|---|---|---|---|
Earthworms | Detritivore | Decaying plant material, soil organic matter | Yes |
Jellyfish | Carnivore | Small fish, plankton, other marine animals | No |
Millipedes | Detritivore | Decaying leaves, dead plant matter on forest floor | Yes |
Seahorses | Carnivore | Tiny shrimp, small crustaceans, plankton | No |
Woodlice | Detritivore | Decaying wood, leaf litter, organic debris | Yes |
Key Characteristics
Primary function: Break down complex organic compounds into simpler forms
Habitat preference: Areas rich in dead organic matter — soil, forest floors, compost
Ecological importance: Speed up decomposition process that would otherwise take years
Nutrient release: Make essential minerals available to plants and primary producers
Trap: Don't confuse carnivores (jellyfish, seahorses) with detritivores — carnivores eat living prey
Trap: Millipedes are detritivores, but centipedes are carnivorous predators
Trap: All decomposer organisms are detritivores, but not all detritivores are primary decomposers
Trophic Levels & Feeding Types
Environment secondary consumers carnivorous
Trophic Levels & Feeding Types in Ecosystems
Trophic levels represent feeding positions in food chains
Primary consumers eat producers; secondary consumers eat primary consumers
Jellyfish and seahorses are secondary consumers (carnivores)
Detritivores operate outside main trophic levels by recycling dead matter
Energy Flow in Ecosystems
%%{init: {"flowchart": {"wrappingWidth": 460}}}%%
flowchart TD
s1["`****Producers** (Autotrophs)**
Plants, algae — convert sunlight to chemical energy`"]
s2["`****Primary Consumers** (Herbivores)**
Eat producers — deer, rabbits, caterpillars`"]
s3["`****Secondary Consumers** (Carnivores)**
Eat primary consumers — jellyfish, seahorses, hawks`"]
s4["`****Tertiary Consumers** (Top Carnivores)**
Eat secondary consumers — sharks, eagles, tigers`"]
s1 --> s2
s2 --> s3
s3 --> s4Feeding Type Classification
Feeding Type | What They Eat | Trophic Level | Examples from Question |
|---|---|---|---|
Herbivores | Living plants, algae | Primary consumers | None in this question |
Carnivores | Living animals | Secondary/tertiary consumers | Jellyfish, seahorses |
Detritivores | Dead organic matter | Outside main levels | Earthworms, millipedes, woodlice |
Omnivores | Both plants and animals | Multiple levels | None in this question |
This question tested the distinction between detritivores (organisms in the decomposer pathway) and carnivorous secondary consumers (organisms in the main food chain). The trap was including jellyfish and seahorses, which are clearly carnivores that feed on living prey, not dead organic matter.
Soil & Forest Floor Invertebrates
Environment Earthworms Millipedes Woodlice
Key Soil & Forest Floor Invertebrates: Ecological Roles
Earthworms are soil engineers that improve soil structure and fertility
Millipedes process leaf litter on forest floors — have many legs
Woodlice (pill bugs) break down decaying wood and organic debris
All three are essential ecosystem engineers in terrestrial habitats
Detailed Species Profiles
Species | Body Type | Habitat | Specific Role | Key Feature |
|---|---|---|---|---|
Earthworms | Segmented worm | Soil layers | Mix soil, create burrows, process organic matter | Castings enrich soil |
Millipedes | Many-legged arthropod | Forest floor, leaf litter | Shred fallen leaves into smaller pieces | Cylindrical body, slow-moving |
Woodlice | Crustacean (isopod) | Under logs, moist areas | Break down decaying wood and bark | Roll into ball when threatened |
Ecological Importance
Soil aeration: Earthworm burrows create channels for air and water movement
Particle size reduction: Millipedes break large leaf pieces into smaller fragments for bacteria
Moisture retention: Woodlice activities help maintain forest floor humidity
Nutrient cycling: All three speed up conversion of complex organics to simple nutrients
Side-by-side photographs showing earthworm in soil, millipede on forest floor with many legs visible, and woodlouse rolled into defensive ball
The three key detritivores from the question — all break down organic matter in terrestrial ecosystems
Trap: Millipedes (many legs, detritivores) vs centipedes (fewer legs, carnivorous predators)
Trap: Woodlice are crustaceans, not insects — they're related to shrimp and crabs
Trap: Don't assume all soil organisms are detritivores — many are predators or parasites
Marine Carnivores
Environment Jellyfish Seahorses
Marine Carnivores: Jellyfish & Seahorses as Secondary Consumers
Jellyfish are cnidarians that capture living prey with stinging tentacles
Seahorses are fish that hunt small crustaceans and plankton
Both are secondary consumers in marine food chains, not detritivores
They represent different phyla but similar trophic roles
Jellyfish vs Seahorses
Characteristic | Jellyfish | Seahorses |
|---|---|---|
Phylum | Cnidaria | Chordata (fish) |
Body structure | Bell-shaped, soft body | Bony plates, prehensile tail |
Hunting method | Stinging tentacles paralyze prey | Suction feeding — rapid mouth expansion |
Primary prey | Small fish, plankton, crustaceans | Tiny shrimp, copepods, larval fish |
Movement | Drift with currents, limited swimming | Poor swimmers — rely on camouflage |
Habitat | Open ocean, coastal waters | Seagrass beds, coral reefs, shallow waters |
Why They're Not Detritivores
Active predation: Both actively hunt and capture living prey, not dead matter
Specialized feeding structures: Stinging cells (jellyfish) and suction mouth (seahorses) are for catching live animals
Energy source: Obtain energy from living tissue, not decomposing organic matter
Ecosystem role: Control populations of small marine organisms, not nutrient recycling
Split image showing jellyfish with extended tentacles capturing small fish, and seahorse using camouflage while hunting tiny crustaceans among seagrass
Both jellyfish and seahorses are active predators of living marine organisms — not detritivores