Why is flow of energy in a food chain considered unidirectional?

Explanation

**Step-by-Step Solution:**

1. **Definition of Food Chain**: A food chain is a linear sequence of organisms where each organism is eaten by the next one in the chain. It illustrates how energy and nutrients flow through an ecosystem.

2. **Understanding Energy Flow**: In a food chain, energy originates from the sun, which is the primary source of energy for all living organisms.

3. **Role of Autotrophs**: The first trophic level consists of autotrophs (producers), such as plants, which use sunlight to produce food through photosynthesis. This process captures solar energy.

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