Those Chordates which have back bone or vertebral or spinal column in their bodies are called vertebrates. Most of chordates belong to the group vertebrata.
Vertebrata is the group of such chordates in which Notochord is replaced by a series of bones called vertebrae which are arranged in the form of a column called vertebral or spinal column. Inside the spinal column nerve cord is present. The brain is also protected in a brain box which is called Cranium.
Classification of Vertebrates:
All Vertebrates are usually classified into the following five classes:
1) Class Pisces (Fishes) (Important Characters)
i. Fishes are aquatic animals (i.e Fresh water and marine).
ii. Their body is stream lines (i.e spindle shaped) which offer less resistance to water, while swimming.
iii. Fishes are cold blooded animals.
iv. They respire by means of gills.
v. Their skin is usually covered with scales.
vi. Heart consists of two chambers i.e one Atrium and one Ventricle.
Sharks, Labeo (Rohu), Trout, Hilsa (Pullah), Dogfish, Cat fish (Khagga)
It is found in fresh water. Labeo is common edible fish. Its gills are covered with bony plates, which are called opercula (Singular: Operculum). The skin is covered with scales, which act as Exoskeleton.
Fishes are very important source of food (having large amount of protein) for animals including man. Many people around the world are involved in fishing industry. Fishing is also a popular game throughout the world.