Which group differs from rest of the three regarding symmetry?

Options

A. Echinoderms
B. Annelids
C. Coelenterates
D. Ctenophores

Answer

To determine which group differs from the rest regarding symmetry, we need to analyze the symmetry characteristics of each group mentioned in the options: Echinoderms, Annelids, Cnidarians, and Ctenophores.

### Step-by-Step Solution:

1. **Understand the Types of Symmetry**:
- **Asymmetry**: Organisms that cannot be divided into identical halves.
- **Bilateral Symmetry**: Organisms that can be divided into identical halves only in one plane.
- **Radial Symmetry**: Organisms that can be divided into identical halves in multiple planes.
- **Biradial Symmetry**: Organisms that exhibit characteristics of both radial and bilateral symmetry.

2. **Analyze Each Group**:
- **Echinoderms**: These are marine invertebrates that typically exhibit radial symmetry as adults (e.g., starfish, sea cucumbers).
- **Annelids**: This group includes earthworms and exhibits bilateral symmetry, meaning they can be divided into two identical halves along one plane.
- **Cnidarians (Cylentrates)**: This group includes jellyfish and corals, which exhibit radial symmetry.
- **Ctenophores**: These are also radially symmetrical organisms, often referred to as comb jellies.

3. **Compare the Symmetry**:
- Echinoderms, Cnidarians, and Ctenophores all exhibit radial symmetry.
- Annelids are unique in this comparison as they exhibit bilateral symmetry.

4. **Conclusion**:
- The group that differs from the rest regarding symmetry is **Annelids** (Option B), as they are the only group that shows bilateral symmetry while the others show radial symmetry.

### Final Answer:
The group that differs from the rest regarding symmetry is **B. Annelids**.

---