Which type of algae are helpful in nitrogen economy :-

Options

A. Green algae
B. Blue green algae
C. Red algae
D. Brown algae

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks which type of algae is beneficial for the nitrogen economy. This implies we need to identify algae that can fix nitrogen.

2. **Analyzing Different Types of Algae:**
- **Green Algae:** These algae do not have any known relation to nitrogen fixation. They do not fix nitrogen, so they can be eliminated as an option.
- **Red Algae and Brown Algae:** Similar to green algae, these types of algae also lack the structures necessary for nitrogen fixation. Thus, they can also be eliminated.

3. **Identifying Blue-Green Algae (BGA):**
- Blue-green algae, also known as cyanobacteria, are capable of fixing nitrogen. They have specialized cells called heterocysts that facilitate this process.
- Heterocysts are specialized cells that provide an anaerobic environment necessary for nitrogen fixation, allowing nitrogen gas (N2) to be converted into ammonia (NH3).

4. **Role of Blue-Green Algae in Nitrogen Fixation:**
- When nitrogen is limited in the environment, blue-green algae like Anabaena can develop heterocysts to fix nitrogen efficiently.
- Blue-green algae can also form symbiotic relationships with other organisms, further enhancing their ability to fix nitrogen.

5. **Conclusion:**
Based on the analysis, the type of algae that is helpful in the nitrogen economy is **blue-green algae (BGA)**.

**Final Answer: Blue-green algae (BGA)**

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