Fish

Fish are aquatic, craniate, gill-bearing vertebrates that lack limbs. Around 99% of all living fish species are ray-finned fish. They are known to be the earliest vertebrates that have existed. Most species of fish, are cold-blooded, allowing their temperatures to vary. Fish are abundant in most bodies of water, found in nearly all aquatic environments, with about 34,000 species classified, they make the largest group of all vertebrate group.