Differentiate between class Chondrichthyes and class Osteichthyes.

1.	Differentiate between class Chondrichthyes and class Osteichthyes.
Answer» Class Chondrichthyes : • Have cartilagenous endoskeleton. • Mouth ventral. • Gill slits without operculum. • Skin has placoid scales. • Usually oviparous, fertilisation internal. • No air bladder, so swim constantly to avoid sinking. • Teeth are backwardly directed, modified placoid scales. • Notochord is persistent throughout life. Males have claspers on pelvicfins. • e.g., Torpedo, Trygon, Scoliodon. Class Osteichthyes : • Have bony endoskeleton. • Mouth is usually terminal. • Four pairs of gill slits covered by operculum. • Skin has cycloid/ctenoid scales. • Usually viviparous, fertilisation external. • Have air bladder which regulates buoyancy. • e.g., Hippocampus, Labeo, Catla, Betta.

Answer»

Class Chondrichthyes :

• Have cartilagenous endoskeleton.

• Mouth ventral.

• Gill slits without operculum.

• Skin has placoid scales.

• Usually oviparous, fertilisation internal.

• No air bladder, so swim constantly to avoid sinking.

• Teeth are backwardly directed, modified placoid scales.

• Notochord is persistent throughout life. Males have claspers on pelvicfins.

• e.g., Torpedo, Trygon, Scoliodon.

Class Osteichthyes :

• Have bony endoskeleton.

• Mouth is usually terminal.

• Four pairs of gill slits covered by operculum.

• Skin has cycloid/ctenoid scales.

• Usually viviparous, fertilisation external.

• Have air bladder which regulates buoyancy.

• e.g., Hippocampus, Labeo, Catla, Betta.

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