Which of the following organism is not radially symmetrical ?

Options

A. Reptiles and birds
B. Snails and insects
C. Insects and birds
D. All of the above

Answer

To solve the question "Which of the following organisms is not radially symmetrical?", we will analyze each option provided:

### Step 1: Understand Radial Symmetry
- **Definition**: Radial symmetry refers to organisms whose body parts are arranged around a central axis, resembling a wheel. These organisms can be divided into multiple identical halves through various planes.
- **Examples**: Common examples include jellyfish and sea anemones.

### Step 2: Analyze the Options
1. **Reptiles and Birds**:
- Both belong to the phylum Chordata.
- They exhibit **bilateral symmetry**, meaning they can be divided into two mirror-image halves along a single plane.
- **Conclusion**: Not radially symmetrical.

2. **Snails and Insects**:
- **Insects**: Belong to the phylum Arthropoda and exhibit bilateral symmetry.
- **Snails**: Generally belong to the phylum Mollusca. While many mollusks exhibit bilateral symmetry, snails can be asymmetrical.
- **Conclusion**: Snails can be asymmetrical, but insects are not radially symmetrical.

3. **Insects and Birds**:
- As discussed, both insects and birds exhibit bilateral symmetry.
- **Conclusion**: Not radially symmetrical.

4. **All of the Above**:
- Since all the organisms listed (reptiles, birds, insects, and snails) do not exhibit radial symmetry, this option suggests that none of them are radially symmetrical.

### Final Conclusion:
- The correct answer is **"All of the above"** because none of the organisms listed exhibit radial symmetry.