The correct option is Earthworm.
Explanation
In an ecosystem, organisms are classified based on their feeding habits and their role in the flow of energy and nutrients. Detritivores (or detritus feeders) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as faeces). They play a critical role in the initial stage of decomposition known as fragmentation.Option Analysis:
- Earthworm Earthworm: Correct. Earthworms are the quintessential terrestrial detritivores. They ingest soil containing decaying organic matter, break it down into smaller particles in their digestive tract, and excrete it. This process increases the surface area for microbial action, facilitating nutrient cycling.
- Mosquito Mosquito: Incorrect. Mosquitoes are not detritivores. Male mosquitoes feed on plant nectar, while female mosquitoes are often ectoparasites that feed on the blood of vertebrates to obtain proteins for egg production.
- Hawk Hawk: Incorrect. A hawk is a carnivore and a predator. It occupies a high trophic level in the grazing food chain, feeding on smaller animals like rodents, birds, or reptiles.
- Eel Eel: Incorrect. Eels are primarily aquatic organisms, whereas the question specifically asks for a terrestrial organism. Furthermore, most eels are carnivorous predators or scavengers, not detritivores in the ecological sense of processing organic detritus.
Key Takeaway:
Detritivores (e.g., earthworms, woodlice, dung beetles) ingest and fragment dead organic matter internally, whereas decomposers (e.g., bacteria, fungi) secrete enzymes to break down organic matter externally and absorb the nutrients.