Final answer:
Birds have nearly hollow bones, an adaptation for flight that reduces weight while maintaining support, contrasting with the denser, marrow-filled bones of mammals. The unidirectional airflow through bird lungs leads to more efficient oxygen transport to cells, necessary for their high metabolic needs during flight.
Step-by-step explanation:
Difference Between Birds and Mammals Regarding Bone Structure
One of the key differences between birds and mammals is related to their skeletal structure. Birds have nearly hollow bones, which are lightweight and filled with air. This adaptation is particularly useful for flight, as it reduces the overall weight of the bird while still providing structural support. In contrast, mammals typically have bones that are denser and filled with marrow, which aids in the production of blood cells and serves as a fat reserve. The hollow, or pneumatic, bones of birds are a unique adaptation that helps them with the energetically taxing process of flying.
While both birds and mammals are endothermic, meaning they can regulate their body temperature, their approaches to respiration also differ. The bird respiratory system is more efficient in transporting oxygen to cells, which is crucial for sustaining high metabolic rates during flight. Birds have air sacs that store inhaled air and push it into the lungs like bellows, maintaining a constant flow of oxygenated air through the lungs even as the bird exhales. This contrasts with mammalian lungs where air flows in a bidirectional way—being inhaled and then exhaled—leading to a less efficient gas exchange compared to birds.