Multiple choice Presence of gill slits in the embryos of all vertebrates support the theory of organic evolution biogenesis metamorphosis recapitulation Reveal answer Fill a bubble to check yourself D Correct answer Explanation The presence of gill slits in vertebrate embryos is a classic example used to support the recapitulation theory (biogenetic law), which suggests that an organism's development (ontogeny) repeats its evolutionary history (phylogeny).