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: -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.

Detailed explanation-3: -Often, these vestigial structures were organs that performed some important functions in the organism at one point in the past. However, as the population changed due to natural selection, those structures became less and less necessary until they were rendered pretty much useless.

Detailed explanation-4: -Vestigial structures are body parts that have lost their use through evolution. Homologous structures are structures that have a common function and suggest common ancestry. Similar embryos suggest that these animals are related and have common ancestors.