Bone marrow does not occur in

Options

A. Reptiles
B. Birds
C. Amphibians
D. Fishes .

Answer

**Step-by-Step Solution:**

1. **Understanding Bone Marrow**: Bone marrow is a soft, spongy tissue found in the center of bones, responsible for producing blood cells.

2. **Identifying the Options**: The question asks where bone marrow does not occur. We need to analyze the options given (not specified in the prompt, but we assume one of them is birds).

3. **Analyzing Bird Anatomy**: In birds, the skeletal structure is adapted for flight. This includes the presence of pneumatic bones, which are bones that are hollow and contain air spaces.

4. **Understanding Pneumatic Bones**: Pneumatic bones are lighter and help reduce the overall weight of the bird, making it easier for them to fly. Due to their hollow nature, these bones do not contain bone marrow.

5. **Conclusion**: Therefore, the correct answer is that bone marrow does not occur in birds due to the presence of pneumatic bones.

**Final Answer**: Bone marrow does not occur in birds.

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