The links at left lead to additional resources to help you learn about the topics in this chapter. These resources include Hot Links to Web sites related to the subject of these topics, the Take It to the Net activities referred to in your textbook, and a Self-Test you can use to test your knowledge of this chapter.
Science News topics pages correlate recently published articles to the topics you are studying.
Section 31-1: Reptiles
A reptile is a vertebrate that has scaly skin, lungs, and eggs with several membranes.
Well-developed lungs; a double-loop circulatory system; an efficient excretory system; strong limbs; internal fertilization; and shelled, terrestrial eggs are the main adaptations that have contributed to the success of reptiles on land.
The four surviving orders of reptiles are lizards and snakes, crocodilians, turtles and tortoises, and the tuatara.
Section 31-2: Birds
Birds are reptilelike 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 for walking or perching, and front limbs modified into wings.
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; and strong chest muscles.