All vertebrates are chordates but all chordates are not vertebrates. Justify the statement.

All chordates have a notochord. Chordates include Urochordates, Cephalochordates (both are called protochordates) and vertebrates. In vertebrates notochord is replaced by vertebral column (backbone), however vertebral column is not present in protochordates. Therefore, all vertebrates are chordates but all chordates are not vertebrates.