In a detrital food chain, dead organic matter of plants and animals is broken down by decomposers, e.g., bacteria and fungi, and moves to detritivores and then carnivores. ... The idea to apply the food chains to ecology and toanalyze its consequences was first proposed by Charles Elton (Krebs 2009).

A detritus food chain is a type of food chain that starts with the decomposition of dead organic matter. It involves the breakdown of dead plants and animals by decomposers, such as bacteria and fungi, into smaller organic particles called detritus. These detritus particles are then consumed by other organisms, which in turn are consumed by larger organisms, creating a chain of energy transfer.

The correct answer to the question is option 'C', bacteria and fungi. Here's an explanation of why:

Decomposers in the Detritus Food Chain:
- Decomposers, such as bacteria and fungi, play a crucial role in the detritus food chain. They break down complex organic matter into simpler compounds, releasing nutrients back into the ecosystem for other organisms to use.

Decomposition of Dead Organic Matter:
- When plants and animals die, they become a source of dead organic matter. This dead organic matter is rich in nutrients, but it needs to be broken down into simpler forms for other organisms to utilize.

Role of Bacteria and Fungi:
- Bacteria and fungi are the primary decomposers in the detritus food chain. They secrete enzymes that break down complex organic molecules, such as proteins, carbohydrates, and lipids, into smaller molecules.
- Bacteria are particularly important in the initial stages of decomposition, as they are efficient in breaking down complex compounds.
- Fungi, on the other hand, are efficient in breaking down tougher materials, such as cellulose and lignin, which are found in plant cell walls.

Detritus Formation:
- As bacteria and fungi decompose the dead organic matter, they convert it into smaller particles called detritus. Detritus consists of partially decomposed organic matter, including dead cells, feces, and other organic debris.
- Detritus can be found in various environments, such as forest floors, aquatic ecosystems, and soil.

Consumption of Detritus:
- Detritus particles are then consumed by other organisms, such as detritivores and scavengers. Detritivores, like earthworms, millipedes, and some insects, directly feed on detritus.
- Other organisms, such as small invertebrates and microorganisms, consume detritus indirectly by feeding on detritivores or by absorbing dissolved organic matter.

Energy Transfer in the Detritus Food Chain:
- The detritus food chain represents a pathway for the transfer of energy and nutrients from dead organic matter to higher trophic levels in the ecosystem.
- Detritus is an important source of energy for many organisms, including those that cannot directly consume living plants or animals.
- Detritivores and other organisms in the detritus food chain play a crucial role in cycling nutrients and maintaining ecosystem health.

In conclusion, a detritus food chain starts with the decomposition of dead organic matter by bacteria and fungi. These decomposers break down complex organic compounds into detritus, which is then consumed by detritivores and other organisms, transferring energy and nutrients through the food chain.