Final answer:
Vestigial structures like whale's hind leg bones are remnants of evolutionary changes from land mammals to fully aquatic whales.
Explanation:
Vestigial structures are reduced and nonfunctional structures in organisms, such as the whale's vestigial leg bones which are remnants from their land-dwelling ancestors. These structures have lost their original function due to evolutionary changes. The evolution from land mammals to fully aquatic whales led to the reduction and disappearance of certain structures like hind leg bones.
Learn more about Vestigial structures and whale evolution here:
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