A food chain starts with......

Options

A. Nitrogen fixation organisms
B. Photosynthesising organisms
C. Consumers
D. Decomposers

Answer

**Step-by-Step Solution:**

1. **Understanding Food Chains**: A food chain represents the flow of energy and nutrients from one organism to another in an ecosystem. It illustrates how different organisms are interconnected through feeding relationships.

2. **Identifying Producers**: In any food chain, the first level consists of producers. Producers are organisms that can create their own food through processes like photosynthesis.

3. **Recognizing Photosynthesizing Organisms**: The primary producers in most ecosystems are photosynthesizing organisms, primarily green plants. They convert sunlight into energy, forming the base of the food chain.

4. **Examining the Options**: The options given are:
- Nitrogen fixation organisms
- Photosynthesizing organisms
- Consumers
- Decomposers

5. **Determining the Correct Answer**: Since food chains start with producers, and the universal producers on Earth are green plants (photosynthesizing organisms), the correct answer is "photosynthesizing organisms."

6. **Conclusion**: Therefore, a food chain starts with photosynthesizing organisms.

**Final Answer**: A food chain starts with **photosynthesizing organisms**.

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