Question

What is a distinctive feature of the chondrichthyans?

1) an amniotic egg
2) unpaired fins
3) an acute sense of vision that includes the ability to distinguish colors
4) a cartilaginous endoskeleton
5) lack of jaws

Answer 1

A distinctive feature of chondrichthyans is their cartilaginous endoskeleton, which differs from the bony skeletons of other fish. They also have paired fins and acute sensory systems.

Step-by-step explanation:

A distinctive feature of the chondrichthyans, such as sharks, rays, and skates, is a cartilaginous endoskeleton. This group of jawed fishes, which are part of the clade Chondrichthyes, is characterized by having paired fins and skeletons made not of bone, but of cartilage. This cartilaginous skeleton can be partially strengthened by granules of calcium carbonate, but it remains distinct from the bony skeletons of other fish, known as Osteichthyes. Unlike the jawless fishes (Agnatha), Chondrichthyes have jaws. Their scales are keel-shaped, which is beneficial for reducing drag and increasing swimming efficiency.