Which class do the majority of fish belong to?

Which class do the majority of fish belong to?

• A. Osteichthyes
• B. Chondrichthyes
• C. Agnatha
• D. Amphibia

Answer: (A)

When scientists classify fish, the big split is between bony fishes and the rest with cartilaginous or jawless skeletons. The group with a bone-based skeleton, Osteichthyes, is by far the most species-rich among fishes. These include the familiar ray-finned and lobe-finned fishes, many of which have a swim bladder for buoyancy and an operculum that protects the gills. In contrast, cartilaginous fishes like sharks and rays have skeletons made of cartilage, and jawless fishes such as lampreys are much fewer in number and more primitive. Amphibians aren’t fishes at all; they’re tetrapods that typically live in water as larvae and on land as adults. So the class that encompasses the majority of fish is Osteichthyes.

When scientists classify fish, the big split is between bony fishes and the rest with cartilaginous or jawless skeletons. The group with a bone-based skeleton, Osteichthyes, is by far the most species-rich among fishes. These include the familiar ray-finned and lobe-finned fishes, many of which have a swim bladder for buoyancy and an operculum that protects the gills. In contrast, cartilaginous fishes like sharks and rays have skeletons made of cartilage, and jawless fishes such as lampreys are much fewer in number and more primitive. Amphibians aren’t fishes at all; they’re tetrapods that typically live in water as larvae and on land as adults. So the class that encompasses the majority of fish is Osteichthyes.