NEET BIOLOGY

Detailed explanation-1: -Notochord. The chordates are named for the notochord: a flexible, rod-shaped structure that is found in the embryonic stage of all chordates and also in the adult stage of some chordate species.

Detailed explanation-2: -Dorsal, rod-like notochord is the primary feature of all chordates. Based on this feature, all animals which show the presence of notochord are grouped under the phylum Chordata.

Detailed explanation-3: -D. A dorsal solid nerve cord. Hint: Animals that belong to the same chordates are fundamentally characterized by the presence of a notochord, a dorsal hollow nerve cord, and paired pharyngeal gill slits.

Detailed explanation-4: -Gill slits vertebral column and notochord.

Detailed explanation-5: -All chordates have a notochord at some stage in their lives, but in some (such as tunicates) the notochord is lost in the adult, whereas in others (such as the vertebrates) the notochord is present in the embryo, but in later stages is largely replaced and surrounded by the vertebrae, or backbones.