Free Response

What are the characteristic features of the chordates?


The characteristic features of the phylum Chordata are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail.

What is the structural advantage of the notochord in the human embryo? Be sure to compare the notochord with the corresponding structure in adults.


The notochord is a flexible structure that provides support for the embryo’s body and formation of the neural tube. In the adults, the notochord has been replaced by the bony, rigid vertebral column. This loss of flexibility restricts the movement of adult humans, and would make it unlikely that the embryo would fit within the small space it is allotted inside the uterus.