How many of the following chordates have flame cells as exretory organ.
Planaria, Ascaris, Amphioxus, Tapeworm, Nereis, Scoliodon.

Options

A. One
B. Two
C. Three
D. Four

Answer

To determine how many of the given chordates have flame cells as excretory organs, we will analyze each organism one by one:

1. **Planaria**:
- Planaria are flatworms and possess flame cells (also known as protonephridia) as their excretory organs.
- **Conclusion**: Yes, Planaria has flame cells.

2. **Ascaris**:
- Ascaris is a roundworm (nematode) and does not have flame cells. Instead, it has a simple excretory system that consists of a canal system.
- **Conclusion**: No, Ascaris does not have flame cells.

3. **Amphioxus**:
- Amphioxus, also known as lancelets, possess flame cells in their excretory system, which is part of their primitive kidney structure.
- **Conclusion**: Yes, Amphioxus has flame cells.

4. **Tapeworm**:
- Tapeworms are also flatworms and have flame cells as part of their excretory system.
- **Conclusion**: Yes, Tapeworm has flame cells.

5. **Nereis**:
- Nereis is a polychaete worm and does not have flame cells. It has a different type of excretory organ called nephridia.
- **Conclusion**: No, Nereis does not have flame cells.

6. **Scoliodon**:
- Scoliodon is a type of shark (cartilaginous fish) and has kidneys as its excretory organs, not flame cells.
- **Conclusion**: No, Scoliodon does not have flame cells.

Now, summarizing the findings:
- Planaria: Yes (flame cells)
- Ascaris: No (no flame cells)
- Amphioxus: Yes (flame cells)
- Tapeworm: Yes (flame cells)
- Nereis: No (no flame cells)
- Scoliodon: No (no flame cells)

**Total organisms with flame cells**: 3 (Planaria, Amphioxus, Tapeworm)

Thus, the answer is **3**.