Researchers have discovered that the ear bones of mammals are homologous to some bones in fish jaws. Which claim is BEST support
ed by this fact? A. Selection pressures have acted over time on mammals but not fish. B. Fish do not require a sense of sound. C. Fish and mammals have a distant common ancestor. D. Selection pressures have promoted similar evolution in fish and mammals.
Answer is C. Fish and mammals have a distant common ancestor.
From jaw bones to ear bones is a rare example of homology in vertebrates. It is fantastic example of evolution in which the structure of the fish jaw correlate to three tiny bones that make up the mammalian ear. It is the transition of the ancestral fish jaw bones into the tiny middle ear bones, which took place as vertebrates came out of the water and starting hearing in air. It reflects their common evolutionary origin.
