All of the following are characteristics of urochordates,except:

Which of the following is $NOT$ a subphylum of Phylum $Chordata$?

In $Urochordata$,the notochord is found in:

In some chordates,the notochord is replaced by the vertebral column. Such animals are called vertebrates. Which one of the following statements is correct?

Differentiate between Invertebrates and Vertebrates.

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ All vertebrates are chordates but all chordates are not vertebrates.
Reason $(R):$ The members of subphylum Vertebrata possess a notochord during the embryonic period; the notochord is replaced by a cartilaginous or bony vertebral column in adults.
In the light of the above statements,choose the correct answer from the options given below: