Identify the phylum in which symmetry is radial in adults but bilateral in larvae.

Options

A. Chordata
B. Craniata
C. Protochordata
D. Echinodermata

Answer

**Step-by-Step Solution:**

1. **Understanding Symmetry**:
- Symmetry in biology refers to the balanced distribution of duplicate body parts or shapes. There are two main types of symmetry: radial and bilateral.
- Radial symmetry means that the organism can be divided into similar halves by multiple planes (like a starfish), while bilateral symmetry means it can only be divided into two equal halves by one plane (like a butterfly).

2. **Identifying the Phylum**:
- The question specifies that we are looking for a phylum where adults exhibit radial symmetry and larvae exhibit bilateral symmetry.
- This characteristic is key to identifying the correct phylum.

3. **Considering Known Phyla**:
- We need to consider various animal phyla. For example, Phylum Chordata and Phylum Arthropoda typically show bilateral symmetry throughout their life stages.
- However, Echinodermata is known for having radial symmetry in adults (like sea stars) and bilateral symmetry in their larval stage.

4. **Conclusion**:
- Based on the characteristics described, the phylum that fits the criteria of having radial symmetry in adults and bilateral symmetry in larvae is **Echinodermata**.

5. **Final Answer**:
- Therefore, the correct answer is **Echinodermata**.

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