AP BIOLOGY

Detailed explanation-1: -Bony fish have lungs which have in many types evolved into a buoyancy aid the swim-bladder. It seems that early stages of bony fish evolution occurred in fresh water where the lung was used for respiration. The lung gradually evolved into a swim-bladder containing gases for buoyancy.

Detailed explanation-2: -Class Osteichthyes includes all bony fishes. Like all fishes, Osteichthyes are cold-blooded vertebrates that breathe through gills and use fins for swimming. Bony fishes share several distinguishing features: a skeleton of bone, scales, paired fins, one pair of gill openings, jaws, and paired nostrils.

Detailed explanation-3: -Tropical reef clown fish, freshwater eels, pelagic swordfish, deep water anglerfish, and river dwelling catfish are all examples of fish in the class Osteichthyes.

Detailed explanation-4: -Air bladder is present in Osteicthyes which regulates buoyancy.