Types of Vertebrates
. There are over 40,000 species of vertebrates, which scientists classify into five groups: (1) fish , (2) amphibians , (3) reptiles , (4) birds , and (5) mammals . Scientists divide fish into three groups based on their anatomy: jawless fish, cartilaginous fish, and bony fish. The other vertebrate groups are made up of tetrapods, which have lungs and generally live on land. Jawless fishes -> Cold-blooded animals that live in water. These fishes have no bone structure and their sole support is from a simple cartilaginous rod known as the notochord. Unlike other vertebrates, these fishes do not have opposing jaws. They have round, sucker-like mouths and use tongues with embedded teeth that scrape tissue from prey. Jawless fishes have primitive breathing openings that provide oxygen to the blood. They reproduce by laying eggs. - Examples: Hagfish, lamprey Cartilaginous fishes -> Cold-blooded animals that live in water. Their notochord is surrounded by rings of cartilage known as