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 listed chordates have flame cells as excretory organs, we will analyze each organism one by one.

### Step-by-Step Solution:

1. **Understanding Flame Cells**:
- Flame cells are specialized excretory cells found in certain invertebrates. They play a crucial role in osmoregulation and the excretion of metabolic waste.

2. **Analyzing Each Organism**:
- **Planaria**:
- Planaria are flatworms that possess flame cells as part of their excretory system. Thus, they have flame cells.
- **Ascaris**:
- Ascaris is a roundworm that does not have flame cells; it has a more complex excretory system involving kidneys. Therefore, Ascaris does not have flame cells.
- **Amphioxus**:
- Amphioxus, also known as lancelets, have flame cells in their excretory system. So, Amphioxus does have flame cells.
- **Tapeworm**:
- Tapeworms are also flatworms and possess flame cells as part of their excretory system. Hence, tapeworms have flame cells.
- **Nereis**:
- Nereis (a type of polychaete worm) does not have flame cells; it has a different type of excretory organ (nephridia). Therefore, Nereis does not have flame cells.
- **Scoliodon**:
- Scoliodon (a type of shark) has a kidney as its excretory organ, not flame cells. Thus, Scoliodon does not have flame cells.

3. **Counting the Organisms with Flame Cells**:
- From the analysis, we found that:
- Planaria: Yes
- Ascaris: No
- Amphioxus: Yes
- Tapeworm: Yes
- Nereis: No
- Scoliodon: No
- Therefore, the organisms that have flame cells are Planaria, Amphioxus, and Tapeworm.

4. **Final Count**:
- Total organisms with flame cells = 3 (Planaria, Amphioxus, Tapeworm).

### Final Answer:
**3 chordates have flame cells as excretory organs.**

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