Q.Choose the term that does not belong in the following group and explain why it does not belong?
Notochord, cephalisation, dorsal nerve cord and radial symmetry

Chordata is the largest, most familiar animal phylum, uniting fishes, amphibians, reptiles, birds and mammals with lancelets and tunicates. Three fundamental features, each present at some stage of the life cycle, define every chordate: an elongated rod-like notochord below the nerve cord and above the gut, serving as a primitive internal skeleton; a dorsal, hollow, tubular nerve cord above the notochord, which enlarges anteriorly into the brain in higher chordates; and pharyngeal gill slits, appearing at some point in every chordate's development, functional as gills in aquatic forms but only transient, non-functional clefts in terrestrial chordates. …