All vertebrates are chordates but all chordates are not vertebrates”. Justify the statement
All vertebrates are chordates : This is so because they possess three basic chordates features as:
(a) All chordates possess a notochord.
(b) All chordates have a dorsal, hollow nerve cord.
(c) All chordates have pharyngeal gill clefts in some stage of their life cycle. All chordates are not vertebrates: Vertebrates have vertebral column but protochordates and agnatha have notochord that is not replaced by vertebral column.