1. The duck-billed platypus and other monotremes differ from other mammals in that they? a. are aquatic. b. have mammary glands. c. lay eggs. d. have hair. 2. The vertebrate group that describes all jawed vertebrates with two pairs of limbs is the? a. craniates. b. mammals. c. tetrapods. d. amniotes. 3. Lampreys differ from fishes in that lampreys a. lack a backbone. b. lack an endoskeleton. c. lack jaws. d. possess a backbone and skull. 4. A biologist visited a fish market and found a fish she did not recognize. To place the unknown fish into a major group, she would need to look at _____. a. only the structure and composition of the skeleton b. the structure and composition of the skeleton and the structure and arrangement of the fins c. only the structure of the fins d. whether a lateral line system was present 5. A key derived character of sharks and rays that distinguishes them from ray-finned fishes is a. calcified (hard) bones. b. jaws and a swim bladder. c. vertebrae. d. a skeleton made of cartilage 6. Which animals are ectothermic? a. turtles and lizards b. birds and mammals c. lizards and birds d. frogs and mammals 7. Which animals are ectothermic? a. turtles and lizards b. birds and mammals c. lizards and birds d. frogs and mammals 8. Which of the following statements best summarizes the difference between ectothermic and endothermic organisms? a. Ectotherms absorb external heat, but endotherms use metabolic heat to maintain a warm, steady body temperature. b. Ectotherms are warm-blooded, but endotherms are cold-blooded. c. Endotherms are warm-blooded, but ectotherms are cold-blooded. d. Endotherms control their temperature, but ectotherms have no control over their temperature.