During early stages of development, dolphin embryos begin to develop hind limbs. By the time the dolphin fetuses are fully developed, the hind limbs have disappeared.

Question

Which statement best explains the early development and then disappearance of hind limbs in dolphins?

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Dolphin fetuses change their development to adapt to an aquatic environment.

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The genes that control the development of hind limbs are destroyed as the fetus develops.

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The early ancestors of dolphins had hind limbs.

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Dolphins are evolving to become terrestrial animals.

Answer 1

The statement that best explains the early development and then disappearance of hind limbs in dolphins is:

The early ancestors of dolphins had hind limbs.

This reflects the concept of evolutionary history, where modern dolphins have retained certain embryonic features that are reminiscent of their distant ancestors, which had hind limbs. As they develop in an aquatic environment, these features are no longer necessary and are subsequently lost.