In Spirogyra

Options

A. The filaments showing scalariform conjugation are homothallic
B. The filaments showing lateral conjugation are homothallic
C. The filaments showing lateral conjugation are heterothallic
D. Asexual reproduction occurs by zoospores

Explanation

### Step-by-Step Solution for the Question on Spirogyra

1. **Identify the Organism**:
- Spirogyra is a freshwater green alga belonging to the class Chlorophyceae. It is characterized by its spiral-shaped chloroplasts.

**Hint**: Remember that Spirogyra is a type of green algae found in freshwater environments.

2. **Reproduction in Spirogyra**:
- Spirogyra reproduces in three main ways: asexual reproduction, vegetative reproduction, and sexual reproduction.
- Asexual reproduction occurs through the formation of zoospores, while vegetative reproduction occurs through fragmentation.

**Hint**: Focus on the different methods of reproduction that Spirogyra utilizes.

3. **Sexual Reproduction**:
- Sexual reproduction in Spirogyra occurs via conjugation, which can be of two types: scalariform conjugation and lateral conjugation.
- In scalariform conjugation, parallel filaments form a conjugation canal, allowing male gametes to transfer to female gametes, resulting in the formation of a zygote.

**Hint**: Understand the difference between scalariform and lateral conjugation in terms of filament arrangement.

4. **Types of Conjugation**:
- **Scalariform Conjugation**: Involves two parallel filaments forming a tunnel-like structure (conjugation canal) for gamete transfer. This is considered heterothallic since it involves different filaments.
- **Lateral Conjugation**: Involves adjacent cells of the same filament, where male gametes fuse with female gametes. This is considered homothallic as it occurs within the same filament.

**Hint**: Differentiate between homothallic and heterothallic conjugation based on whether the gametes come from the same or different filaments.

5. **Conclusion**:
- The correct statement regarding Spirogyra is that filaments showing lateral conjugation are homothallic. This means that the reproduction occurs within the same filament.

**Hint**: Pay attention to the definitions of homothallic and heterothallic to answer questions correctly.

### Final Answer
The correct answer is: **Filaments showing lateral conjugation are homothalic.**