Explain how animals in Vertebrata are classified into further subgroups.

Vertebrata has two main subclasses namely,
Pisces ( which have a streamlined body with tails and fins that helps them in swimming) and tetrapod ( which have four limbs for their movement).

The tetrapod animals are further classified into:

1. Amphibia : The animals belonging to this group are adapted to live in both land and water. They can breathe under the water through their skin and can breathe through the lungs when they are present on the land. They are cold-blooded and require an aquatic habitat to lay eggs. These organisms are mainly characterized by the presence of two pairs of limbs, smooth and moist skin for respiration.

2. Reptilia : The organisms of this group crawls for their movement. They are cold-blooded and are characterized by the presence of scales on their skin. Reptiles also lack an external ear and some reptiles such as snakes pick up vibrations through the ground.

3. Aves : The forelimbs of these organisms are modified into wings which help them in their flight. Most members of this group have a streamlined body which is specially designed to offer low air resistance during flight. Feathers play an important role in flight, thermal insulation and water-proofing. They are warm-blooded and are thus able to regulate their body temperature. Aves have beak which help them in preening and feeding.

4. Mammalia : These organisms are distinguished by the presence of mammary glands. They have two pairs of limb for walking, grasping, swimming etc. Skin is covered by hair and they have an external ear called pinnae. They are warm-blooded and viviparous in nature.