fish.

iintroduction

fish, diverse group of animals that live and breathe in water. all fishes are vertebrates animals with backbones with gills for breathing. most fish have fins for swimming, scales for protection, and a streamlined body for moving easily through the water.
fishes live in nearly every underwater habitat, from near-freezing arctic waters to hot desert springs from mud in dried-up tropical ponds to the deepest ocean abyss. special antifreeze chemicals in the blood of antarctic icefish enable them to survive in water below 0 c 32 f. desert pupfish found in hot springs of western north america live in temperatures higher than 40 c 100 f. killifish release their eggs, or spawn, as the dry season begins in the tropics of south america and africa, leaving their eggs to dry in the ground until the rains return six months later. in the deep ocean, where sunlight never reaches, many fishes cooperate with glowing bacteria to create their...