Brian Berg, age 8, of Denton, Texas, for his question:

HOW MANY KINDS OF LIZARDS ARE THERE?

Lizards are reptiles that are closely related to snakes. Scientists have identified about 3,000 different kinds of lizards. Most of them live in the tropics and the warm parts of the temperate zones. They are the most common reptile found in deserts.

In the northeastern part of the United States, many people mistake salamanders for lizards. Few lizards live in this area, but there are many salamanders. The salamander is commonly called the "spring lizard" or "wood lizard."

Lizards are cold blooded animals. They cannot keep their bodies much warmer or cooler than their surroundings. They have dry, scaly skin.

Most lizards live on the ground or in trees. Those that spend much time in trees are called geckos. Their feet have soft pads with tiny, brush like hooks. Geckos have claws that they can draw in as a cat does. The animal can walk upside down on a ceiling or cling to a pane of glass.