1. Many snakes can survive eating just once every few weeks. Why can’t birds do this? 2. Birds and mammals are both endotherms, and they both have a four-chambered heart. Why are birds classified as...

1. Many snakes can survive eating just once every few weeks. Why can’t birds do this?

2. Birds and mammals are both endotherms, and they both have a four-chambered heart. Why are birds classified as reptiles rather than as mammals?

3. Birds have hollow bones, an adaptation for flight. How do hollow bones help birds fly?