All classes included in the Phylum Chordata share which of the following key common features?
The Phylum Chordata is a major taxonomic grouping characterized by the presence of a notochord and a dorsal hollow neural system at some stage in the organism's life cycle. Because diverse classes such as fishes, amphibians, reptiles, birds, and mammals all exhibit these defining features, they are unified under this single phylum.
Ref: NCERT Class 11 Biology