Choose the correct statements :
I. Cartilaginous fish swims continously due to the presence of an air bladder.
II. Osteichthyes have four pairs of gills that are covered by an operculum.
III. The notochord is persistent throughout life in Chondrichthyes.
IV. Teeth of cartilaginous fishes are modified placoid scales.

Select the option with a correct representation of an animal to the below-mentioned class of vertebrates: I. The jawless animal in which the body is devoid of scales and paired fins. II. They have four pairs of gills that are covered by an operculum. III. The body is covered by dry and cornified skin, epidermal scales or scutes. IV. Skin is dry without glands and long bones are hollow with air cavities.

Select the option with a correct representation of an animal to the below-mentioned class of vertebrates: I. The jawless animal in which the body is devoid of scales and paired fins. II. They have four pairs of gills that are covered by an operculum. III. The body is covered by dry and cornified skin, epidermal scales or scutes. IV. Skin is dry without glands and long bones are hollow with air cavities.

Due to the absence of air bladder, fishes belonging to the class Chondrichthyes have to swim constantly. How important is the presence of air bladder in these fishes?

Which of the following are correct regarding Osteichthyes? I. They are also called bony fishes. II. They are also called bony fishes. III. They are also called cartilaginous fishes. IV. They include sharks, rays and rat fishes.

Which of the following is/are not the characteristics of the Class Osteichthyes? (i) Body is streamlined and mouth is terminal. (ii) Gills are convered by operculum. (iii) Skin convered with cycloid and placoid scales. (iv) Many of them are viviparous.

Which of the following is/are not the characteristics of the Class Osteichthyes? (i) Body is streamlined and mouth is terminal. (ii) Gills are convered by operculum. (iii) Skin convered with cycloid and placoid scales. (iv) Many of them are viviparous.

Which of the following is/are not the characteristics of the Class Osteichthyes? (i) Body is streamlined and mouth is terminal. (ii) Gills are convered by operculum. (iii) Skin convered with cycloid and placoid scales. (iv) Many of them are viviparous.