528 Vertebrate Animals Fish, amphibians, reptiles, birds, and mammals are all vertebrate animals. SECTION 1 Chordate Animals Main Idea Vertebrates have an internal system of bones including a backbone. SECTION 2 Amphibians and Reptiles Main Idea Amphibians and reptiles are both egg-laying, exothermic vertebrates. SECTION 3 Birds Main Idea Birds are the only animals with feathers. SECTION 4 Mammals Main Idea Mammals’ body systems are adapted to their environment. Traits We Share With Animals An eagle flies through the sky, a salmon swims through a stream, a snake slithers along the ground, and a grizzly bear walks along a river’s edge. Each of these animals appears different, but these animals, as well as humans, share a common trait—an internal skeleton. What other traits do these animals and humans share? Science Journal Tom & Pat Leeson
