Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Branchiostoma is classified as a chordate but it is not a vertebrate. Reason (R): In Branchiostoma, the notochord is present only in the embryonic stage and gets replaced by a vertebral column in the adult. In the light of the above statements, choose the most appropriate answer from the options gi

Step-by-step solution

Assertion (A) is correct because Branchiostoma belongs to the subphylum Cephalochordata, which is a group of protochordates. Therefore, it is a chordate but not a vertebrate. Reason (R) is incorrect because in Cephalochordates like Branchiostoma, the notochord extends from the head to the tail region and is persistent throughout their life. It is not replaced by a vertebral column. The replacement of the embryonic notochord by a cartilaginous or bony vertebral column in adults is a characteristic feature of the sub