Question

Detritus food chain starts with:

• A. Living producers
• B. Dead organic matter
• C. Herbivores
• D. Carnivores

Hint:

DFC = Dead organic matter $\rightarrow$ Detritivores $\rightarrow$ Predators.
GFC = Green plants $\rightarrow$ Herbivores $\rightarrow$ Carnivores.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Ecosystems have two main energy pathways: the Grazing Food Chain (GFC) and the Detritus Food Chain (DFC).

Step 2: Detailed Explanation:
The Grazing Food Chain begins with living primary producers (plants) and solar energy.
In contrast, the Detritus Food Chain (DFC) begins with dead organic matter (detritus), such as leaf litter, dead animals, and organic waste.
This dead matter contains stored chemical energy that is utilized by detritivores (e.g., earthworms) and decomposers (e.g., bacteria, fungi).
Energy flows from these decomposers to small carnivores that feed on them.
In many terrestrial ecosystems, the DFC is the major pathway for energy flow because most of the plant biomass dies without being eaten by herbivores.

Step 3: Final Answer:
The starting point and primary energy source for a detritus food chain is non-living, dead organic matter.

Answer 2

The word detritus itself refers to worn-down or decayed matter, and checking each option against that meaning identifies the correct starting point of this food chain.

1. Living producers: Living plants capturing sunlight describes the starting point of the grazing food chain, where energy enters through photosynthesis in an organism that is still alive. This is a separate pathway from the one built on decayed matter.
2. Dead organic matter: This is precisely what the term detritus describes, fallen leaves, animal carcasses, and waste material. Detritivores such as earthworms and decomposers such as fungi and bacteria feed directly on this material, breaking it down and releasing nutrients, with energy then passing on to small carnivores that prey on the detritivores.
3. Herbivores: Herbivores feed on living plant tissue and belong to the grazing food chain as the first consumer level, not to the detritus pathway, and they are never the starting point of any food chain since they are consumers rather than a source of stored organic matter.
4. Carnivores: Carnivores sit even further along either food chain, consuming herbivores or detritivores, so they cannot mark the beginning of a chain.

Only dead organic matter matches both the literal meaning of detritus and the actual first feeding step used by detritivores and decomposers.

Hence, the correct answer is Dead organic matter.