AP BIOLOGY

Detailed explanation-1: -The correct answer is: evolution from a distant common ancestor. It has been shown that most of vertebrate embryos such as fish, reptiles, amphibians, birds, and mammals’ embryos begin with a basically similar structure: they have gill arches, notochords, spinal cords, and primitive kidneys.

Detailed explanation-2: -Similarities in embryos are evidence of common ancestry. All vertebrate embryos, for example, have gill slits and tails (see the Figure below). Most vertebrates, except for fish, lose their gill slits by adulthood. Some of them also lose their tail.

Detailed explanation-3: -All vertebrate embryos develop tails, though adult humans retain only the coccyx. All vertebrate embryos show gill slits, though these develop into gill openings only in fish and larval amphibians. In humans, gills slits form the lower jaw and Eustachian tube.

Detailed explanation-4: -All vertebrate embryos have gill arches, notochords, spinal cords, and primitive kidneys.

Detailed explanation-5: -Similar anatomy across different species highlights their common origin and can be seen in homologous and vestigial structures. Embryology provides evidence for evolution since the embryonic forms of divergent groups are extremely similar.