Explain how animals in Vertebrata are classified into further subgroups.

Vertebrates are classified into further subgroups on following bases: 

1. Pisces: The body is streamlined. Muscular tail is present which assists in locomotion. Body is covered with scales. Paired gills are present; which can breathe oxygen dissolved in water. They are cold-blooded animals. The heart has only two chambers. They lay eggs. 

2. Tetrapoda: Animals have four limbs for locomotion and hence the name tetrapoda. Tetrapoda is divided into four classes, viz. amphibia, reptilia, aves and mammalia. 

(a) Amphibia: These animals are adapted to live both in water and land. Mucus glands on skin keep the skin moist. The animals breathe through skin when in water and through lungs when on land. The heart has three chambers. These are cold blooded animals. Examples: Frog, toad, salamander, etc. 

(b) Reptilia: These animals show crawling movement for locomotion. Skin is hardened to form scales. Most of the reptilians have three chambered heart but crocodile has four-chambered heart. They don’t need water to lay eggs, rather eggs are covered with hard shells and laid on land. Examples: snakes, lizards, crocodile, turtle, etc. 

(c) Aves: The body is covered with feathers. Forelimbs are modified into wings. These are warm-blooded animals. The heart has four chambers. Bones are hollow (pneumatic); which assists in flying. All the birds belong to this class. 

(d) Mammalia: The body is covered with hairs. Skin has seat glands and sebaceous glands. Mammary glands are present in females and are used for nourishing the young ones. Most of the mammalians give birth to young ones and are called viviparous. Some of the mammals lay eggs and are called oviparous. Examples: human, chimpanzee, lion, platypus, horse, etc.

Vertebrates are classified into further subgroups on following bases: 

1. Pisces: The body is streamlined. Muscular tail is present which assists in locomotion. Body is covered with scales. Paired gills are present; which can breathe oxygen dissolved in water. They are cold-blooded animals. The heart has only two chambers. They lay eggs. 

2. Tetrapoda: Animals have four limbs for locomotion and hence the name Tetrapoda. Tetrapoda is divided into four classes, viz. amphibia, reptilia, aves and mammalia. 

a. Amphibia: These animals are adapted to live both in water and land. Mucus glands on skin keep the skin moist. The animals breathe through skin when in water and through lungs when on land. The heart has three chambers. These are cold-blooded animals. 

Examples: Frog, toad, salamander, etc. 

b. Reptilia: These animals show crawling movement for locomotion. Skin is hardened to form scales. Most of the reptilians have three-chambered heart but crocodile has four-chambered heart. They don’t need water to lay eggs, rather eggs are covered with hard shells and laid on land. 

Examples: snakes, lizards, crocodile, turtle, etc. 

c. Aves: The body is covered with feathers. Forelimbs are modified into wings. These are warm-blooded animals. The heart has four chambers. Bones are hollow (pneumatic); which assists in flying. All the birds belong to this class. 

d. Mammalia: The body is covered with hairs. Skin has seat glands and sebaceous glands. Mammary glands are present in females and are used for nourishing the young ones. Most of the mammalians give birth to young ones and are called viviparous. Some of the mammals lay eggs and are called oviparous. 

Examples: human, chimpanzee, lion, platypus, horse, etc.

Animals in Vertebrata are classified into five classes:
(i) Class Pisces: This class includes fish such as Scoliodon, tuna, rohu, shark, etc. These animals mostly live in water. Hence, they have special adaptive features such as a streamlined body, presence of a tail for movement, gills, etc. to live in water.
(ii) Class Amphibia: It includes frogs, toads, and salamanders. These animals have a dual mode of life. In the larval stage, the respiratory organs are gills, but in the adult stage, respiration occurs through the lungs or skin.
They lay eggs in water.
(iii) Class Reptilia : It includes reptiles such as lizards, smakes, turtles, etc. They usually creep or crawl on land. The body of a reptile is covered with dry and cornified skin to prevent water loss. They lay eggs on land.
(iv) Class Aves: It includes all birds such as sparrow, pigeon, crow, etc. Most of them have feathers. Their forelimbs are modified into wings for flight, while hind limbs are modified for walking and clasping. They lay eggs.
(v) Class Mammalia : It includes a variety of animals which have milk producing glands to nourish their young ones. Some lay eggs and some give birth to young ones. Their skin has hair as well as sweat glands to regulate their body temperature.

The major characteristics used to classify animals in vertebrata are-1 . The king exosheleton or endoskeleton, 2. The king of respiratory organs,3. The method of reproduction and givin birth to yound ones. On the bais of above mentioned characters the vetebrata is divided into following classes:
(i) Exoskeleton of scales , Endskeloton of cartilage or bones , Breating through gill.....PISCES (Fishes)
(ii) Breathing through gill only in larva , Skin slimy....AMPHIBA
(iii) Exoskeletone of scales , Laying eggs outside the water ....REPTILIA.
(iv) Exoskeleton fo fethers , Lay eggs, fight possible ..... ...... AVES (Birds)
(v) Exoskeleton of hairs , External ears , Give birth to youn ones .....MAMMALIA