Bone marrow does not occur in

Options

A. Reptilia
B. Amphibia
C. Fishes
D. Birds

Answer

**Step-by-Step Solution:**

1. **Understanding Bone Marrow**: Bone marrow is a semi-solid tissue located within the spongy portion of bones. It plays a crucial role in the production of blood cells, a process known as hematopoiesis.

2. **Identifying the Role of Bone Marrow**: In mammals and birds, bone marrow is the primary site for the formation of new blood cells. This includes red blood cells, white blood cells, and platelets.

3. **Differences in Bone Structure**: The structure of bones in birds differs from that in mammals. Birds have adaptations that allow them to fly, which include lighter bones.

4. **Understanding Pneumatic Bones**: Many bones in birds are pneumatic, meaning they are hollow and filled with air sacs. This adaptation helps reduce weight and aids in respiration during flight.

5. **Conclusion**: Since birds have pneumatic bones that do not contain bone marrow, the answer to the question "Bone marrow does not occur in" is **birds**.

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