Sea urchin and heart urchin are present in

Options

A. Crinoidea
B. Asteroidea
C. Holothuroidea
D. Echinoidea.

Answer

**Step-by-Step Solution:**

1. **Identify the Organisms**: The question asks about the sea urchin and heart urchin. The scientific name for sea urchin is *Echinus* and for heart urchin, it is *Echinocardium*.

2. **Classify the Organisms**: Both *Echinus* and *Echinocardium* belong to the same class. To determine the class, we need to look at the classification of these organisms within the phylum Echinodermata.

3. **Understand the Phylum Echinodermata**: Echinodermata is a phylum that includes spiny-bodied marine animals. This phylum is divided into five classes.

4. **List the Classes of Echinodermata**:
- Class 1: Asteroidea (includes starfishes)
- Class 2: Ophiuroidea (includes brittle stars)
- Class 3: Echinoidea (includes sea urchins and heart urchins)
- Class 4: Holothuroidea (includes sea cucumbers)
- Class 5: Crinoidea (includes feather stars and sea lilies)

5. **Identify the Correct Class**: Since both the sea urchin (*Echinus*) and heart urchin (*Echinocardium*) are mentioned as being part of the class that includes urchins, we conclude that they belong to Class 3, which is Echinoidea.

6. **Final Answer**: Therefore, the sea urchin and heart urchin are present in the class Echinoidea.

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