Explain how animals in Vertebrata are classified into further subgroups.

Explanation

The subphylum vertebrata has been classified into two Superclasses, namely, Agnatha and Gnathostomata, on the basis of presence or absence of jaws and paired appendages. Agnatha does not have jaws and paired appendages while gnathostomata bear jaws and paired appendages.
Superclass Gnathostomata is further classified into Pisces, Amphibia, Reptilia, Aves and Mammalia. The major characteristics used to classify are :
(i) Exoskeleton of scales, Endoskeleton of cartilage or bones, Breathing through gills-Pisces (fishes).
(ii) Breathing through gills only in larva, Skin slimy - Amphibia.
(iii) Exoskeleton of scales, Laying eggs outside the water-Reptilia.
(iv) Exoskeleton of feathers, Lay eggs, Flight possible - Aves (Birds).
(v) Exoskeleton of hairs, External ears , Give birth to young ones-Mammalia.