The structure present in cyanobacteria (BGA) that helping in nitrogen fixation is

Options

A. chlamydospore
B. akinete
C. iodia
D. heterocysts

Answer

**Step-by-Step Solution:**

1. **Understanding Cyanobacteria**:
- Cyanobacteria, also known as blue-green algae, are prokaryotic organisms that can perform photosynthesis. They contain chlorophyll, specifically chlorophyll A, which is similar to that found in green plants.

2. **Nitrogen Fixation**:
- Nitrogen fixation is the process of converting atmospheric nitrogen (N₂) into a form that can be utilized by living organisms, typically ammonia (NH₃). Certain organisms, including some cyanobacteria, have specialized structures that facilitate this process.

3. **Identifying Specialized Structures**:
- In cyanobacteria, the specialized cells that are responsible for nitrogen fixation are called heterocysts. These cells provide an anaerobic environment that is essential for the nitrogen-fixing bacteria to function, as nitrogenase, the enzyme responsible for nitrogen fixation, is sensitive to oxygen.

4. **Examples of Cyanobacteria with Heterocysts**:
- Notable examples of cyanobacteria that contain heterocysts include Nostoc and Anabaena. These organisms can be found in various environments, including freshwater, marine, and terrestrial ecosystems.

5. **Conclusion**:
- Therefore, the structure present in cyanobacteria that helps in nitrogen fixation is the heterocyst.

**Final Answer**: The structure present in cyanobacteria (BGA) that helps in nitrogen fixation is **heterocyst**.

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