If you ask people to list six animals, they will probably mention a dog, cat, horse, lion, bird and snake. Very few people would answer rattlesnake, clam, earthworm, mosquito, ostrich, or jellyfish. Yet all are members of the wonderful and vast kingdom of animals. The other kingdom is made of plants. Following two basic guidelines, it is easy to tell large animals from plants. The first guideline is movement; any natural form that moves itself about is probably an animal. The other guideline is the ability to eat food; that is, any natural form that eats and digests food is probably an animal. There are exceptions to both of these rules, like in the case of tiny forms of life, but for the most part they hold true.

The big animal kingdom is divided into groups called classes. Fish is one class. Insects are another class. We ourselves belong to the class called mammals, along with the horses, elephants, monkeys and many others (mammals or animals that nurse their young on milk). Together, the members of this animal kingdom offer a wondrous variety of life.

The largest animals that have ever lived on land were the dinosaurs. The biggest dinosaur was more than 100 feet long and other dinosaurs stood 20 feet tall. Yet, there were other dinosaurs only a foot or so long. All the dinosaurs died out about 65 million years ago. The dinosaurs are classified as reptiles and are related to the ancestors of living reptiles like our snakes and crocodiles. Among the largest living reptiles are the giant sea turtle which may be 8 feet long and the American and Orinoco crocodiles that can grow up to 23 feet long. The largest snakes are the pythons and boas which are members of the same family. Among these, the largest to date would be the South American boa (or the Anaconda) that can grow to more than 40 feet long. The largest bird is the ostrich, which does not fly but can run fast. Among the largest flying birds are the condors of California and South America. The albatross has the largest wingspan and the male trumpeter swan is the heaviest bird at 40 pounds. Even the American bald eagle does not weigh more than 12 pounds.

Today, other large animals continue to exist on land. They are the great whales-- mammals, as it happens. The biggest whale is the blue whale which grows to more than 100 feet long and can weigh about 115 tons, or as much as 1300 men. Next to whales, the largest living animals are the whale shark and the basking shark, though they are classified as fishes. The whale shark may be 50 feet long, while the basking shark can reach a length of 45 feet. Several other large animals also inhabit the oceans. The giant squid can be 50 feet long when its arms are outstretched. The giant clam in the tropics can grow up to 5 feet in diameter and can weigh 500 pounds. The North Atlanta giant jellyfish can also weigh a ton. Its body is 8 feet wide and its tentacles can be 120 feet long.

The largest land mammal to live in our century is the African elephant. Some of these elephants have grown as high a 13 feet. The Indian elephant is only a bit smaller. It grows up to 10 feet high and weighs up to six tons. In contrast, the smallest mammals are the shrews, especially the Etruscan shrew that lives in southern Europe and weighs less than a dime.

Every class of animals has its own small and miniature kind. Most of the smaller animals consist of insects and one-celled animals like an amoeba. The smallest forms of animal life are one- celled creatures that can only be seen with a microscope. They can also be so small that they can live in blood cells. For example, some of these small creatures cause the disease called kala azar, which is widespread in Asia. These creatures are so small that it would take 6000 of them placed side-by-side measure an inch.