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 determine which organism is not radially symmetrical, we need to understand the concepts of symmetry in organisms. Here’s a step-by-step solution:

### Step 1: Understand Symmetry
- **Symmetry** refers to the balanced proportions of an organism. There are different types of symmetry: radial symmetry, bilateral symmetry, and asymmetry.
- **Radial Symmetry**: An organism exhibits radial symmetry if it can be divided into similar halves by multiple planes passing through its center. This is common in organisms like jellyfish (Cnidarians) and starfish (Echinoderms).
- **Bilateral Symmetry**: An organism exhibits bilateral symmetry if it can only be divided into two identical halves along one plane. This is typical in organisms like humans, insects, and other vertebrates.

### Step 2: Identify Organisms
- The question provides options that may include various organisms. We need to classify these organisms based on their symmetry.
- Common examples of radially symmetrical organisms include:
- Cnidarians (e.g., jellyfish, corals)
- Echinoderms (e.g., starfish)
- Ctenophores (e.g., comb jellies)

### Step 3: Analyze the Options
- If the options include organisms such as:
- **Sponges**: Asymmetrical
- **Cnidarians**: Radially symmetrical
- **Echinoderms**: Radially symmetrical
- **Mollusks (e.g., snails)**: Bilaterally symmetrical
- **Insects**: Bilaterally symmetrical
- **Reptiles and Birds**: Bilaterally symmetrical

### Step 4: Determine the Answer
- From the analysis, organisms like reptiles, birds, snails, and insects do not exhibit radial symmetry. They are either asymmetrical or bilaterally symmetrical.
- Therefore, the answer to the question "Which of the following organism is not radially symmetrical?" would be **D, all of the above** (if all listed organisms are non-radially symmetrical).

### Conclusion
The organisms that are not radially symmetrical include reptiles, birds, snails, and insects.

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