Explain how animals in Vertebrata are classified into further subgroups.

Vertebrates are categorised using a variety of features, including an exoskeleton, respiratory systems, a manner of giving birth, a heart with a certain number of chambers, a mode of life, etc. Vertebrata animals are primarily divided into six classes:

1. Cyclostomes: The modified and degenerated outgrowth of the original stalk of a vertebrate is seen in the cyclostomata. They are called Cyclostomes due to their round mouth. Since they are parasitic, they typically feed on adult fish. They resemble eels morphologically. Their name, Agnatha, derives from the fact that they are the only living vertebrates lacking true jaws. Ex: Hagfishes and lampreys.
2.  Pisces: They are cold-blooded, aquatic creatures. Two chambers make up their heart. They have scales or plates covering their bodies. They produce eggs and breathe through gills. They have cartilage as part of their endoskeleton. Ex: Fishes: Shark, Rohu, Tuna
3.  Amphibians: These cold-blooded creatures can be found both on land and in water. Gills, lungs, and skin are all used for respiration. They have a heart with three chambers. Ex: Frog, Toad, Salamander
4.  Reptiles: These animals are cold blooded. They breathe through their lungs and have a three chambered heart. Ex: Snakes, Lizards
5. Aves: These oviparous vertebrates with warm-blooded animals are covered in feathers. They breathe via their lungs and have a four chambered heart. Ex: Sparrow, Eagles
6. Mammals: These warm-blooded, four-chambered animals are mammals. They reproduce viviparously and have hair on skin and pinna. Ex: Tiger, Humans, Deer