How are Sharks so Flexible?
Dear Digger Doug,
How are sharks so flexible?
—Jackson, Montgomery, AL
Thank you for asking this interesting question. The skeleton of a shark is different from the skeletons of other fish, because a shark skeleton has only cartilage and no bones. Cartilage is stretchy, flexible tissue. Most cartilage in humans is replaced as they grow. Sharks enjoy their cartilage, however, because it is lighter than bone, and keeps them from sinking. Some of their cartilage is also enhanced with calcium salts, giving it the strength of bone.
The shark’s swimming muscles are attached to its thick skin instead of being attached to bones. This means that the shark uses less energy as it swims. God designed the shark with the perfect physical qualities for survival. These traits could not have evolved.