What is primary source of energy in a detritus food chain ?

Explanation

### Step-by-Step Solution:

1. **Understanding Food Chains**: In any food chain, energy flows from one trophic level to another. The primary source of energy in a typical food chain is usually autotrophs, such as plants, which convert sunlight into energy through photosynthesis.

2. **Defining Detritus Food Chain**: A detritus food chain is a type of food chain that begins with dead organic matter. This can include dead plants, animals, and other organic materials.

3. **Identifying the Primary Source of Energy**: In a detritus food chain, the primary source of energy is not sunlight or living plants, but rather the dead organic matter itself. This dead organic matter serves as the initial energy source for decomposers and detritivores.

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