Photosynthesis first occurred in

Options

A. Cyanobacteria
B. Green plants
C. Mycoplasma
D. Green algae

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: We need to identify which organism first performed photosynthesis among the given options: A) Cyanobacteria, B) Green plants, C) Mycoplasma, D) Green algae.

2. **Historical Context**: Photosynthesis is believed to have first occurred around 3.2 to 3.5 billion years ago. This timeframe is crucial for determining which organisms were present at that time.

3. **Identifying Organisms**:
- **Cyanobacteria**: These are blue-green bacteria known for their ability to perform photosynthesis. They were present on Earth around 3.5 billion years ago.
- **Green Plants**: These organisms are much more recent, appearing only about 0.15 billion years ago (150 million years ago).
- **Mycoplasma**: This is a type of bacteria that lacks a cell wall and can survive without oxygen. They are not known for photosynthesis and are also relatively recent.
- **Green Algae**: These organisms appeared around 0.5 billion years ago (500 million years ago), which is still after the initial occurrence of photosynthesis.

4. **Conclusion**: Given that cyanobacteria were present and capable of photosynthesis around 3.5 billion years ago, they are the correct answer to the question of which organism first performed photosynthesis.

5. **Final Answer**: **A) Cyanobacteria**.

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