Except for the Hagfish,lamprey,and Their Close Relatives,all Vertebrates Have Paired

question 51

Multiple Choice

Except for the hagfish,lamprey,and their close relatives,all vertebrates have paired jaws; how did jaws evolve within an evolutionary clade that already had a skeleton?

• A) A mutation causing extraskeletal cell division allowed the extra cells to form the jaws.
• B) A modification of an existing skeletal element occurred; in this case, the gill arch was modified.
• C) Reproduction between a nonjawed chordate and a jawed arthropod produced jawed offspring.
• D) To date, biologists have been unsuccessful in explaining the origin of jaws.

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