Verterates

Vertebrates An animal with cartilaginous or bony vertebrae that surrounds a nerve cord and its brain protected by a skull is called a vertebrate. A taxonomic class of animals known as the Subphylum Vertebrate is where all the vertebrates belong to (Klappenbach, n.d.). In other words, vertebrate are animals with backbones. Vertebrates are divided into five sub groups, which are the fish, amphibian, reptiles, birds and mammals.
The first class of vertebrate is the fish. Classification of vertebrates (n.d.) states that fish is a kind of aquatic vertebrate with special characteristics that allow them to spend all or part of their lives in water which is their habitat. “Aquatic" means they spend their lives in water (The five classes of vertebrates, 2009). According to The five classes of vertebrates (2009), fishes are ectothermic vertebrates which mean that fishes are cold-blooded vertebrate. Fish’s body temperature is equal to the surrounding environment. The characteristics of the fish’s body make it able to easily facilitate movements through the water mainly because of its body shape. The tail is a chief "organ" of locomotion, meanwhile the fins are used to steer, swim, and maintain balance. Overlapping slimy scales cover the body of most fish, though some fish, like sharks, have rough leathery skin (Classification of vertebrates, n.d.). Gills act as the breathing organ of fishes. These special organs called gills enable fishes to perform the gas exchange between water and fish blood. They enable the fish to breathe oxygen in water. For most fishes, their gills are protected by covers called opercula. When water enters a fish's mouth, it passes over the gills where tiny blood vessels absorb oxygen from the water and release carbon dioxide into it. Water is then expelled through the gill slits (Classification of vertebrates, n.d.). For the method of reproduction, Classification of vertebrates (n.d.) states that fishes are categorised into two categories,