Fish is a kind of vertebrate animals. Vertebrate animals are kinds of animals that have a backbone. This animal is also included in the group of cold-blooded animals (poikilothermic). Fish has very much species. More than 27,000 species of fish scattered around the world. Based on the type of bones, they are classified into 3 types they are jawless fish (class Agatha, 75 species including lampreys and hagfish), cartilaginous fish (class Chondrichthyes, 800 species including sharks and rays), and the rest belong to bony fishes (class Osteichthyes).
