Question

Write two salient features of chordates.

Answer 1

Vertebrates are members of the phylum Chordata and kingdom Animalia. Animals that possess bilateral symmetry can be divided into two groups: deuterostomes and protostomes, based on the patterns of embryonic development. The deuterostomes, meaning second mouth, consist of two phyla: Echinodermata and Chordata. Echinoderms are invertebrate marine animals that have a spiny body covering and pentaradial symmetry, a group that includes sea cucumbers, sea stars and sea urchins. The most familiar and conspicuous members of Chordata are vertebrates, but this phylum also consists of two groups of invertebrate chordates.

Complete answer:
Animals in the phylum Chordata share four key features which appear at some stage during their development: a dorsal hollow nerve cord, a notochord, a post-anal tail and pharyngeal slits. In some groups of animals, some of these features are present only during embryonic development.
The chordates are named for the notochord, which is a rod-shaped, flexible structure that is found during the embryonic stage of all chordates and in some chordate species during the adult stage. It is located between the nerve cord and the digestive tube, and provides skeletal support through length of the body. In some chordates, throughout an animal’s lifetime, the notochord acts as the primary axial support of the body. In vertebrates, notochord can be seen during embryonic development, at that time it induces the development of neural tubes and serves as a support for the embryonic body development. The notochord is not found during the postnatal stage of vertebrates; at this point, it is replaced by the vertebral column, that is, spine.
During development, the dorsal hollow nerve cord is derived from an ectoderm which rolls into a hollow tube. It is located dorsal to the notochord in chordates. But, other animal phyla are characterized by the solid nerve cords that are located either laterally or ventrally. In most chordate embryos, the nerve cord is developed into the spinal cord and brain, which compose the central nervous system.

Note: Other two features of chordates are: pharyngeal slits and post anal tail. Pharyngeal slits are the openings in pharynx that extend to the outside environment. Pharyngeal slits allow water to exit that enters the mouth during feeding in organisms that live in aquatic environments. The post anal tail is the posterior elongation of body, extending beyond the anus. The tail contains muscles and skeletal elements, which provide a source of locomotion in aquatic species like fishes.