Hydra is constituted under phylum coelenterate because it possesses

Options

A. Mesogloea
B. Nematocysts
C. Body cavity
D. Tentacles.

Answer

**Step-by-Step Solution:**

1. **Identify the Phylum**: Hydra is classified under the phylum Coelenterata, which is also known as Cnidaria.

2. **Understand the Characteristics**: The defining characteristic of the phylum Cnidaria is the presence of specialized cells known as cnidocytes (or nidoblasts). These cells contain structures called nematocysts.

3. **Function of Nematocysts**: Nematocysts are specialized cells that can release a stinging thread when triggered by mechanical or chemical stimuli. This mechanism serves multiple purposes: defense against predators, capturing prey, and anchoring the organism.

4. **Location of Nematocysts**: In Hydra, these nematocysts are primarily located in the epidermis, particularly in the tentacles and body.

5. **Conclusion**: The presence of nematocysts is the key reason why Hydra is classified under the phylum Coelenterata (Cnidaria). Thus, it is the presence of these specialized stinging cells that constitutes Hydra under this phylum.

**Final Answer**: Hydra is constituted under phylum Coelenterata because it possesses specialized stinging cells called nematocysts.

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