Question

Adult tunicates are sessile, have no notochord, have only a simple neural net, and do not have a tail; however, they do have pharyngeal slits. Why are these animals classified as chordates?A. Pharyngeal slits are the most prominent features of chordates.B. These creatures are not chordates.C. The adult form exhibits pharyngeal slits, which are only found in chordates.D. The mobile larval form has all the chordate features.

Answer 1

Although adult tunicates are invertebrates, the tunicates are considered as chordates. Therefore, B is wrong.

Pharyngeal slits are a feature of chordates, but it is not the most prominent one. Also, to be considered a chordate, having only pharyngeal slits is not enough. Therefore, A is wrong too and C is also incorrect.

To be considered a chordate, a creature must present four structures: a notochord, a dorsal hollow nerve cord, a tail and pharyngeal slits. In adults only the pharyngeal slit is present, but the larval form presents all of those features.

Therefore, the correct answer is D. The mobile larval form has all the chordate features.