MEDIUM. The theory of recapitulation, also called the biogenetic law or embryological parallelism is often expressed in Ernst Haeckel's phrase as "ontogeny recapitulates phylogeny". Both fish and bird embryos exhibit gill slits and a tail. All vertebrate embryos follow a common developmental path due to their common ancestry. For example, all vertebrate embryos have "gill slits" which are not actually gills. Since Darwin's time, textbooks have reiterated that early embryos of many vertebrates, including humans, have tiny pouches that reflect an evolutionary fish stage. Mayr is not claiming that human embryos actually have the gill slits of a fish. Reason for incorrect answer: Option a. is given as, “backbone.” Backbone is the property of vertebrates and all chordates are not vertebrates. Explanation: According to embryology, all vertebrates exhibit similar traits and structures at their embryonic stage. Embryos of all vertebrates have deep structural similarities and these deep similarities are said to clearly show evidence for evolutionary relationships. Darwin’s theory of biological evolution noted that all vertebrates have gill slits and tails in early stages of embryo formation, even though these features may be lost or modified in … Answer. The embryos of birds and mammals clearly show gill-like structures, more technically called pharyngeal arches. So what makes a chordate, a chordate? The nerve cord, notochord, postnatal tail, and pharyngeal slits are the four characteristics that are present in the chordates. A. Recapitulation. More recently, embryologists … Example: All vertebrates embryos have gill slits, which may become gills or ear bones. B. Organic evolution. German zoologist Ernst Haeckel is perhaps most famous for defending evolution with the argument that creatures replay their evolutionary past when developing in the womb. Animals in the phylum Chordata share four key features that appear at some stage during their development: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and; a post-anal tail. The vertebrae and nervous systems develop early so all embryos appear to have a tail. D. Biogenesis. All vertebrate embryos follow a common developmental plan due to having a set of genes that gives the same instructions for development. Embryos of many different kinds of animals: mammals, birds, reptiles, fish, etc. The development of the human embryo reveals steady progress toward a fully functional human body. The so-called gill slits of a human embryo have nothing to do with gills, and the human embryo does not pass through a fish stage or any other evolutionary stage. Like all chordates, vertebrates have a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. look very similar and it is often difficult to tell them apart. So, the embryo of all chordates does not have a backbone. As chordates, all vertebrates have a similar anatomy and morphology with the same qualifying characteristics: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. It becomes very difficult to differentiate between the embryos of a fish, and that of a bird, or embryo of a fish, and a human. Many traits of one type of animal appear in the embryo of another type of animal. For example, fish embryos and human embryos both have gill slits. They connect the throat to the outside early in development but eventually close in many species; only in fish and larval amphibians do they contribute to the development of gills. C. Metamorphosis. The most conspicuous and familiar members of Chordata are vertebrates, but not all have vertebrae. The presence of gill slits in the embryos of all vertebrates supports the theory of. 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