Kitty Shelton, age 9, of Jackson, Miss., for her question:
DO ALL ANIMALS HAVE TEETH?
Not all animals have teeth. Birds, turtles, certain anteaters and adult whalebone whales do not have teeth. Most of the other animals have highly specialized teeth that allow them to do certain kinds of jobs or to eat certain kinds of food.
Lion and tigers, for example, eat only meat. They have long, pointed teeth to tear their prey apart. Horses and cows, on the other hand, eat only plants. They have short, flat teeth that grind leafy foods. Beavers use their large, strong teeth to gnaw through tree trunks.
Many animals use their teeth as weapons and to hold captured prey. And many only use their teeth to chew up their food.
The teeth of most fish are finely pointed. Fish use their teeth for grasping food, not chewing. But some fish have rounded teeth with which they can crush and grind food.
Mammals have fewer teeth than do fish. Most mammals have two sets of teeth: a primary set that is replaced by a permanent set in adulthood. In some, the permanent set continues to grow throughout the animal's life.
For example, beavers would soon wear down their incisors by their constant gnawing on tree trunks and branches. But the incisors continue to grow as long s the animal lives. An elephant's tusks, which really are long, curved teeth, also grow as long as the elephant lives.
An elephant's tusks are the largest teeth on any land animal. The elephant uses the tusks to fight and also to dig for food.
Animal teeth are subject to many of the same diseases as are those of man. When decay, abscesses and defective teeth occur in animal pets and livestock, veterinarians treat or remove the teeth.
A snake's fangs are actually teeth. They fold back when the snake closes its mouth. Venom spurts through grooves in the fangs when a snake bites.
A garfish has many rows of teeth. If one tooth is lost, another moves into its place.
Many insects have large, hard jaws that they use for chewing by moving them sideways. But some, such as dragonflies, have sharp teeth for biting and chewing.
Scientists who study prehistoric man often become specialists in tooth and jaw structures. Because teeth are the hardest substance in the body, they frequently survive under. conditions that destroy all other parts of the body.
For example, all that remains of the Heidelberg Man, who lived about 375,000 years ago, are the lower jaw and teeth.
Among the largest human teeth that scientists have found are those of the Java Man, who lived about 1.5 million years ago. The Cro Magnon Man, who lived between about 35,000 and 8,000 B.C., had shorter, smaller teeth, similar to those of modern man.
Large teeth and jaws, the scientists tell us, were important to primary man as weapons and as tools. As man developed other tools and began to grow his own food, his teeth became less important and did not need to grow so large.