The wheel organ is found in:

Select the correct option for the animal given below.

All vertebrates are chordates but all chordates are not vertebrates. Explain.

Which of the following is a Cephalochordate?

Which of the following animals possesses a post-anal tail?

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 $(R)$: Notochord is replaced by vertebral column in the adult vertebrates.
In the light of the above statements,choose the most appropriate answer from the options given below: