Question

Which extant chordate group is postulated to be most like the earliest chordates in appearance?

A) Cephalochordata
B) adult Urochordata
C) Amphibia
D) Reptilia
E) Chondrichthyes

Answer 1

Option A). The Cephalochordata, such as lancelets, are the extant chordate group most similar to the earliest chordates, possessing key chordate features in their adult form.

Step-by-step explanation:

A) Cephalochordata is the extant chordate group thought to resemble the earliest chordates in appearance the most. The clade's members, like lancelets, have the characteristic notochord, dorsal hollow nerve cord, pharyngeal slits, and post-tail of chordates in their adult form. Based on molecular analyses and the finding of fossils such as Haikouella, it is likely that Cephalochordata and the ancestral form from which vertebrates descended are closely related. Hence, Option A) is the correct answer.