Animals on the MoveIt looked like a scene from “Jaws” but without the dramatic mus
Animals on the Move
It looked like a scene from “Jaws” but without the dramatic music. A huge shark was lowly swimming through the water, its tail swinging back and forth like the pendulum of a clock.
Suddenly sensitive nerve ending in the sharks skin picked up vibrations of a struggling fish. The shark was immediately transformed into a deadly, efficient machine of death. With muscles taut, the shark knifed through the water at a rapid speed. In a flash the shark caught its victim, a large fish, in its powerful jaws. Then, jerking its head back and forth, the shark tore huge chunks of flesh from its victim and swallowed them. Soon the action was over.
Moving to Survive
In pursuing its prey, the shark demonstrated in a dramatic way the important role of movement, or locomotion, in animals.
Like the shark, most animals use movement to find food. They also use locomotion to escape enemies, find a mate, and explore new territories. The methods of locomotion include crawling, hopping, slithering, flying, swimming, or walking.
Humans have the added advantage of using their various inventions to move about in just about any kind of environment. Automobiles, rockets, and submarines transport humans from deep oceans to as far away as the moon. However, for other animals movement came about naturally through millions of years of evolution. One of the most successful examples of animal locomotion is that of the shark. Its ability to quickly zero in on its prey has always impressed scientists. But it took a detailed study by Duke University marine biologists S. A． Wainwright, F． Vosburgh, and J. H. Hebrank to find out how the sharks did it. In their study the scientists observed sharks swimming in a tank at Marine land in Saint Augustine, Fla. Movies were taken of the sharks’ movements and analyzed. Studies were also made of shark skin and muscle.
Skin Is the Key
The biologists discovered that the skin of the shark is the key to the animal’s 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.
The Duke University biologists have found that the greatest stretching occurs where the shark bends its body while swimming. During the body’s 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 shark’s body snaps back the other way.
As energy is alternately stored and released on both sides of the animal’s 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
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.
When the shark swims slowly, the pressure on the fibers is relatively low. The fibers are more relaxed, and the shark is able to bend its body at sharp angles. The animal swims this way when looking around for food or just swimming. However, when the shark detects an important food source, some fantastic involuntary changes take place.
The pressure inside the animal may increase by 10 times. This pressure change greatly stretches the fib
A．to find food
B．to avoid being chased by its enemies
C．to find a new place to live
D．to show its braveness
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