Skin Is the Key
C) The biologists discovered that the skin of the shark is the key to the animals high efficiency in swimming through the water. The skin contains many fibers that crisscross like the inside of a belted radial tire. The fibers are called collagen fibers. These fibers can either store or release large amounts of energy depending on whether the fibers are relaxed or taut. When the fibers are stretched, energy is stored in them the way energy is stored in the string of a bow when pulled tight. When the energy is released, the fibers become relaxed.
D) The Duke University biologists have found that the greatest stretching occurs where the shark bends its body while swimming. During the bodys back and forth motion, fibers along the outside part of the bending body stretch greatly. Much potential energy is stored in the fibers. This energy is released when the sharks body snaps back the other way.
As energy is alternately stored and released on both sides of the animals body, the tail whips strongly back and forth. This whip-like action propels the animal through the water like a living bullet.
Source of Energy
E) What causes the fibers to store so much energy? In finding the answer the Duke University scientists learned that the sharks similarity to a belted radial tire doesnt stop with the skin. Just as a radial tire is inflated by pressure, so, too, is the area just under the sharks collagen radials. Instead of air pressure, however, the pressure in the shark may be due to the force of the blood pressing on the collagen fibers.
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