Question

How does class Agnatha (jawless fish) differ from class Osteichthyes (bony fish)?

1) Agnatha have no jaws while Osteichthyes have jaws
2) Agnatha have cartilaginous skeletons while Osteichthyes have bony skeletons
3) Agnatha have no paired fins while Osteichthyes have paired fins
4) Agnatha have no scales while Osteichthyes have scales

Answer 1

Class Agnatha (jawless fish) lacks jaws, has no internal ossification or paired fins, and no scales, unlike Class Osteichthyes (bony fish), which have jaws, bony skeletons, paired fins, and scales.

Step-by-step explanation:

The class Agnatha (jawless fish) differs from the class Osteichthyes (bony fish) in several ways:

• Agnatha, such as lampreys and hagfish, have no jaws, while Osteichthyes are characterized by having jaws.
• The skeletons of Agnatha are not bony; they typically lack internal ossification, whereas Osteichthyes have skeletons that are chiefly composed of bone.
• Agnatha do not possess paired fins as found in Osteichthyes, which sport paired pectoral and pelvic fins.
• Agnatha species have smooth skin without scales, in contrast to the scales present on most Osteichthyes.

These differences highlight fundamental divergences in their evolution, anatomy, and ecology. The jawless fish, being one of the earliest forms of vertebrates, provide a glimpse into the ancient features of vertebrate life, while Osteichthyes show significant evolutionary advancements such as the development of jaws and a bony skeleton.