Question

A marine biologist catches a species of fish she has never seen before. Upon examination, she determines that the species has a predominantly cartilaginous skeleton and a swim bladder. If its pectoral fins are not fused with its head, to which category of fish does the specimen belong?

a) Chondrichthyes
b) Osteichthyes
c) Agnatha
d) Sarcopterygii

Answer 1

The fish with a cartilaginous skeleton and a swim bladder, and unfused pectoral fins, belongs to the category of Osteichthyes, specifically to the clade Actinopterygii, which includes ray-finned fishes. Hence, the correct answer is option (b).

Step-by-step explanation:

If a marine biologist catches a species of fish that has a predominantly cartilaginous skeleton and a swim bladder, and its pectoral fins are not fused with its head, the specimen likely belongs to the category of Osteichthyes, specifically to the clade Actinopterygii, which includes ray-finned fishes. This deduction is based on the presence of a swim bladder, an organ not found in the cartilaginous fishes of the class Chondrichthyes.

Members of Chondrichthyes, which include sharks, rays, skates, and ghost sharks, lack a swim bladder and have skeletons made entirely of cartilage, while bony fishes (Osteichthyes) have skeletons made predominantly of bone and typically possess a swim bladder. The presence of pectoral fins that are not fused with the head is another characteristic common to Actinopterygii.