Which of the followingis first oxygenic photosynthetic organism?

Options

A. Green algae
B. Red algae
C. Blue-green algae
D. Golden algae

Answer

To determine the first oxygenic photosynthetic organism from the given options, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Term 'Oxygenic Photosynthesis':**
- Oxygenic photosynthesis is a process where organisms convert light energy into chemical energy, producing oxygen as a byproduct.

2. **Identify the Organisms Listed:**
- The options provided are:
- Green algae
- Red algae
- Blue-green algae (Cyanobacteria)
- Golden algae

3. **Research the Organisms:**
- **Green Algae:** These are primarily aquatic and are known for their chlorophyll content, but they are not the first to perform oxygenic photosynthesis.
- **Red Algae:** These are also aquatic and contain phycoerythrin, but they are not the earliest oxygenic photosynthetic organisms.
- **Blue-Green Algae (Cyanobacteria):** These are considered the first organisms to perform oxygenic photosynthesis, releasing oxygen into the atmosphere.
- **Golden Algae:** These are a group of algae that also perform photosynthesis but are not the first to do so.

4. **Conclude Based on Historical Evidence:**
- Cyanobacteria, or blue-green algae, are known to have existed over 2.5 billion years ago and played a crucial role in the Great Oxygenation Event, which transformed Earth's atmosphere by increasing oxygen levels.

5. **Select the Correct Answer:**
- Based on the information gathered, the correct answer is **Blue-Green Algae (Cyanobacteria)**.

### Final Answer:
The first oxygenic photosynthetic organism is **Blue-Green Algae (Cyanobacteria)**.

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