What is a Bird?<br />Birds are reptile like animals that maintain a constant internal body temperature. They have an outer covering of feathers; two legs that are covered with scales and are used to walking or perching; and front limbs modified into wings.<br />
Feathers<br />Feathers are made mostly of protein and develop from pits in the birds skin.<br />----------><br />
The Evolution of Birds<br /><ul><li>Paleontologists agree that birds evolved from extinct reptiles.
Evidence for this hypothesis is provided by many embryological, anatomical, and physiological characteristics shared by modern birds and living reptiles. </li></li></ul><li>Forms, function, and Flight<br /><ul><li> Birds have a number of adaptations that enable them to fly. These adaptations include highly efficient digestive, respiratory, and circulatory systems; aerodynamic feathers and wings; strong, lightweight bones; and strong chest muscles.</li></li></ul><li>Body temperature Control<br /><ul><li> Animals that can generate their own body heat which is called endotherms.
Endotherms, which include birds , mammals, and some other animals, have high rates of metabolisms compared to ectoderms such As reptiles.</li></ul>How birds are related to reptiles <---------<br />
Feeding<br /><ul><li>Any body heat that a birds loses must be gained by eating food. The more food a bird eats, the more heat energy its metabolism can generate.
In fact, the title “eats like a bird” it is quite misleading, because most birds are voracious eaters.</li></li></ul><li>Also the birds feeding process<br /><ul><li>Birds that eat insects or seeds, however, have a muscular organ called the gizzard that helps in the mechanical breakdown of </li></ul>food.<br /><ul><li>The crop is located at the lower end of the esophagus. Food is stored and moistened in the crop as well.</li></li></ul><li>Respiration<br /><ul><li>Birds have a unique and highly efficient way of taking in oxygen and eliminating carbon dioxide.
Air sacs: when a bird inhales, most air enters large posterior air sacs in the body cavity and bones. </li></li></ul><li>The Systems<br />Circulation: Birds have four chambered hearts and two separates circulatory loops.<br />Excretion: The excretory system of many birds are similar to those of most living reptiles.<br />Response: Birds have well-developed since organs, which are adaptations that enable them to coordinates the movement required for flight.<br />Movements: Birds that can not fly,getaround mostly by walking, running and sometimes swimming.<br />Reproduction: In birds, both male and female reproductive tracts open into the cloaca.<br />