Nematocysts occur in phylum

Options

A. Coelenterata
B. Nematoda
C. Porifera
D. Annelida.

Answer

**Step-by-Step Solution:**

1. **Understanding Nematocysts**: Nematocysts are specialized cells that contain a coiled, barbed structure used for capturing prey and defense. They are commonly found in certain aquatic organisms.

2. **Identifying the Phylum**: The question asks in which phylum nematocysts occur. The options provided are:
- Coelenterata
- Nematoda
- Porifera
- Annelida

3. **Analyzing Each Option**:
- **Coelenterata**: This phylum includes organisms like jellyfish, corals, and hydras. They are known for having nematocysts (also known as cnidocytes) that help in capturing prey.
- **Nematoda**: This phylum includes roundworms. They do not possess nematocysts.
- **Porifera**: This phylum includes sponges, which lack true tissues and do not have nematocysts.
- **Annelida**: This phylum includes segmented worms like earthworms, which also do not have nematocysts.

4. **Conclusion**: Based on the analysis, the only phylum that contains nematocysts is Coelenterata. Therefore, the correct answer is Coelenterata.

**Final Answer**: Nematocysts occur in the phylum **Coelenterata**.

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