Final answer:
The main difference between the traditional and cladistic classifications of chordates is in their evolutionary history. Cladistics focuses on evolutionary relationships using derived characteristics, whereas traditional systems may consider physical traits more broadly.
Step-by-step explanation:
The difference between the traditional and cladistic classification of chordates and their extant sister groups is a difference in b. Evolutionary history. Traditional classification systems may rely on physical characteristics and overall similarities, whereas cladistics is an approach that focuses on the evolutionary relationships between different organisms, using shared derived characteristics to establish a phylogenetic tree.
In the context of chordates, cladistics has examined the evolutionary ties within the phylum Chordata, which encompasses both invertebrate clades such as Urochordata (tunicates) and Cephalochordata (lancelets), as well as the vertebrates or Craniata.