Vertebrates

"jawless fishes"

"jawed vertebrates, which include the cartilaginous fishes (sharks, rays, and ratfish)"

"tetrapods, which include amphibians, reptiles, birds and mammals"

"bony fishes"

"So vertebrates like us are unusually huge and unusually fragile, have rela­tively simple life cycles, and are built from the least common type of cell. The fact that we are not the standard mode of life is important to remember."