[Campbell Biology P.774] According to the provided text and figure, what is the prevailing h... | Practice Question

According to the provided text and figure, what is the prevailing hypothesis regarding the evolutionary origin of gnathostome jaws?

  • A: Jaws evolved from the modification of existing skeletal rods that previously supported anterior pharyngeal (gill) slits.
  • B: Jaws developed directly from the cranium as a novel structure to aid in feeding.
  • C: Jaws originated from specialized dental elements similar to those found in conodonts.
  • D: Jaws are a result of the enlargement of the gnathostome forebrain, enhancing feeding capabilities.

Explanation

The text states: 'According to one hypothesis, gnathostome jaws evolved by modification of the skeletal rods that had previously supported the anterior pharyngeal gill slits.' Figure 34.13 illustrates this process, showing skeletal rods being modified into precursors of jaws.