AP BIOLOGY

Detailed explanation-1: -These unused structures without function are called vestigial structures. Other examples of vestigial structures are wings (which may have other functions) on flightless birds like the ostrich, leaves on some cacti, traces of pelvic bones in whales, and the sightless eyes of cave animals.

Detailed explanation-2: -The existence of vestigial organs can be attributed to changes in the environment and behaviour patterns of the organism in question. As the function of the structure is no longer beneficial for survival, the likelihood that future offspring will inherit the “normal” form of the structure decreases.

Detailed explanation-3: -A vestigial structure is a biological structure that has lost a major ancestral function and is usually drastically reduced in size. Well-known examples include the eyes of blind cave fishes and blind cave salamanders, and the diminutive wings of kiwis and emus.