__________ is/are absent in Echinoderms but present in mollusca

Options

A. Larval stage
B. Flame cells
C. Locomoty organs
D. Excretory organs

Answer

To solve the question, we need to identify what is absent in Echinoderms but present in Mollusca. Let's analyze the options step by step:

1. **Understanding Echinoderms and Mollusca**:
- Echinoderms include organisms like starfish, sea urchins, and sea cucumbers. They have a unique water vascular system and do not possess a specialized excretory system.
- Mollusca includes organisms like snails, clams, and octopuses. They have a well-developed excretory system.

2. **Analyzing the Options**:
- **Option A: Larval stage**: Both Echinoderms and Mollusca have larval stages in their life cycles.
- **Option B: Flame cell**: Flame cells are specialized excretory structures found in some invertebrates, particularly in flatworms, not in Mollusca.
- **Option C: Locomotory organ**: Both groups have locomotory organs; Echinoderms have tube feet, while Mollusca have a muscular foot.
- **Option D: Excretory organ**: Mollusca possess a proper excretory system, including structures like kidneys (metanephridia), while Echinoderms lack specialized excretory organs.

3. **Conclusion**: Based on the analysis, the correct answer is that the excretory organ is absent in Echinoderms but present in Mollusca.

Final Answer: **Excretory organ**