Chameleon - biology.

Chameleon - biology. Chameleon, common name for certain lizards that are well known for their ability to change colors. The chameleon changes color when it is frightened and in response to light, temperature, and other environmental changes. The color change is caused by hormones that affect special pigment-bearing cells in the skin. Its color does not always change to match its surroundings, however, as is commonly believed. The chameleon has a remarkably long, sticky tongue, which darts into the air to catch insects. Its body is unusually shaped, and most chameleons are specially adapted to living in trees. The lizard's long, thin legs raise it from the ground, and its toes are divided into opposable sets of two and three digits that enable it to grasp branches rather than cling to them as with claws. The strong, curled tail is also adapted to grasping. Many chameleons have large domed, or casqued, heads, and males may have as many as three horns, sometimes used for combat. One striking three-horned species is Jackson's chameleon of Africa. The chameleon has a short neck that is of limited mobility; however, the eyes are big and can move independently of each other in many directions. The chameleon has no external eardrum, or tympanic membrane. Chameleons range in size from just a few centimeters to as large as 63 cm (25 in). More than 100 species of true chameleons exist. They are found in Africa, Madagascar, Spain, southern Europe, Arabia, India, Sri Lanka, and the Seychelles Islands. Several color-changing lizards in the United States, commonly called anoles, are also popularly called chameleons. Scientific classification: Chameleons constitute the subfamily Chamaeloninae of the family Chamaelonidae. Jackson's chameleon is classified as Chamaeleo jacksoni. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.