AP BIOLOGY

Detailed explanation-1: -All vertebrate embryos, for example, have gill slits and tails. Most vertebrates, except for fish, lose their gill slits by adulthood. Some of them also lose their tail. In humans, the tail is reduced to the tail bone.

Detailed explanation-2: -All vertebrate embryos have gill arches, notochords, spinal cords, and primitive kidneys.

Detailed explanation-3: -These slits are found in the embryos of all vertebrates because they share as common ancestors the fish in which these structures first evolved.

Detailed explanation-4: -The first stage in vertebrates is called neurulation, where the neural plate folds forming the neural tube (see above). Other common organs or structures that arise at this time include the heart and somites (also above), but from now on embryogenesis follows no common pattern among the different taxa of the animalia.

Detailed explanation-5: -So, the correct answer is ‘Recapitulation’