Anoxygenic photoautotroph requires

Options

A. `O_2, H_2O` & light
B. `CO_2 and H_2O`
C. `CO_2` and light
D. `CO_2," light, "H_2S`

Answer

**Step-by-Step Solution:**

1. **Understanding Photoautotrophs:**
- Photoautotrophs are organisms that can synthesize their own food using light energy. This process involves converting light energy into chemical energy, primarily in the form of carbohydrates.

2. **Types of Photoautotrophs:**
- There are two main types of photoautotrophs:
- **Oxygenic Photoautotrophs:** These organisms, such as green plants, use water as an electron donor during photosynthesis, resulting in the production of oxygen as a by-product.
- **Anoxygenic Photoautotrophs:** These organisms do not produce oxygen during photosynthesis. Instead, they utilize different electron donors.

3. **Requirements for Anoxygenic Photoautotrophs:**
- Anoxygenic photoautotrophs require:
- **Light Energy:** Essential for the photosynthesis process.
- **Carbon Dioxide (CO2):** Serves as a carbon source for synthesizing carbohydrates.
- **Electron Donor:** Unlike oxygenic photoautotrophs that use water, anoxygenic photoautotrophs can use alternative electron donors such as hydrogen sulfide (H2S) or other chemicals.

4. **Conclusion:**
- Therefore, the correct answer to the question "Anoxygenic photoautotroph requires" is:
- **Carbon Dioxide (CO2)**
- **Light Energy**
- **Electron Donor (e.g., H2S)**

**Final Answer:**
Anoxygenic photoautotroph requires carbon dioxide, light, and H2S (option 4).

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