Larva of which phylum showing bilateral symmetry but adult are radial symmetry ?

Options

A. Crinoidea
B. Asteroidea
C. Ophioroidea
D. Echinoderma

Answer

### Step-by-Step Solution:

1. **Understanding Symmetry**:
- Begin by defining the two types of symmetry mentioned in the question: bilateral symmetry and radial symmetry.
- **Bilateral Symmetry**: An organism exhibits bilateral symmetry if it can be divided into two identical halves along one plane. This means that the left and right sides are mirror images of each other.
- **Radial Symmetry**: An organism with radial symmetry can be divided into similar halves by multiple planes passing through the central axis. This means that any cut through the center will yield equal parts.

2. **Identifying the Phylum**:
- The question asks for a phylum where the larvae exhibit bilateral symmetry and the adults exhibit radial symmetry.
- The only phylum that fits this description is **Echinodermata**.

3. **Characteristics of Echinodermata**:
- Echinodermata is a phylum that includes marine animals such as starfish, sea urchins, and sea cucumbers.
- The larvae of echinoderms show bilateral symmetry, which is common in many larval forms across different phyla.
- As they mature into adults, they exhibit radial symmetry, which is characteristic of adult echinoderms.

4. **Conclusion**:
- Based on the definitions and characteristics discussed, the answer to the question is that the larvae of the phylum **Echinodermata** show bilateral symmetry while the adults exhibit radial symmetry.

### Final Answer:
The larvae of the phylum **Echinodermata** show bilateral symmetry, while the adults exhibit radial symmetry.

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