1. Tardigrade
  2. Question
  3. Biology
  4. Choose the correct statements: I. Cartilaginous fish swims continuously 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.

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Q. Choose the correct statements:
I. Cartilaginous fish swims continuously 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.

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Solution:

Due to absence of air bladder in cartilaginous fishes, they have to swim constantly to avoid sinking. They have usually five pairs of gill slits which are separate and are without operculum.