During early stages of development, dolphin embryos being 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?

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

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

Dolphins are evolving to become terrestrial animals.

The early ancestors of dolphins had hind limbs.

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 development and atavism, where traits from ancestral species are present during the early stages of development but may not be expressed in the fully developed organism. In the case of dolphins, their ancestors were terrestrial mammals that had hind limbs, and some of the developmental pathways still reflect that ancestral trait before it is suppressed or modified for adaptation to an aquatic lifestyle.