In which alga sexual reproduction takes place by conjugation ?

Answer

**Step-by-Step Solution:**

1. **Identify the Type of Reproduction**: The question asks about sexual reproduction in algae, specifically focusing on the process of conjugation.

2. **Recognize the Alga in Question**: The alga that is known for sexual reproduction through conjugation is Spirogyra.

3. **Describe the Structure of Spirogyra**: Spirogyra has a simple structure characterized by spiral-shaped chloroplasts and filamentous forms.

4. **Explain the Process of Conjugation**:
- Two Spirogyra filaments align next to each other.
- A connection is formed between them, often referred to as a conjugation tube or channel.
- Through this channel, the gametes (reproductive cells) or cytoplasm from one filament is exchanged with the other.

5. **Completion of Conjugation**: After the exchange of gametic material, fertilization occurs, leading to the formation of new progeny or structures.

6. **Conclusion**: Therefore, the alga in which sexual reproduction takes place by conjugation is Spirogyra.

**Final Answer**: Spirogyra

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