Class Reptilia 3 main features that help them survive on land 1. amniotic egg – waterproof egg with a shell 2. internal fertilization – sperm is deposited in the female and the swims to the egg. External fertilization that occurs in most fishes and amphibians would not work on land. 3. Water-tight skin – prevents dehydration. Reptiles have scales (hard overlapping structures made up of the protein keratin) 4. All reptiles, birds, and mammals (these organisms are collectively called amniotes) have the characteristics described above.

Class Reptilia Ectothermic Have lungs throughout their lives Examples: –Snakes –Lizards –Turtles –Crocodiles –Alligators

Class Aves (birds) Endothermic (warm-blooded) Characteristics: –Feathers –Lightweight, hollow bones –Beak, no teeth –Hard-shelled eggs

Birds Birds lack teeth (makes them lighter ). Instead they have a gizzard. A gizzard is a muscular organ, often containing small stones that is used to grind up seeds and other foods. Most birds have a crop as well. A crop is a sac-like organ used for temporarily storing food.