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 :
- A
Both (A) and (R) are correct and (R) is the correct explanation of (A)
- B
Both (A) and (R) are correct but (R) is not the correct explanation of (A)
- C
(A) is correct but (R) is not correct
- D
(A) is not correct but (R) is correct
Phylum Chordata is divided into three subphyla: Urochordata, Cephalochordata, and Vertebrata. Only members of Vertebrata possess a vertebral column in the adult. Members of the other two subphyla retain a notochord but do not develop a vertebral column.
So all vertebrates are chordates, but not all chordates are vertebrates. Assertion (A) is correct.
In adult vertebrates, the notochord present during embryonic development is replaced by a bony or cartilaginous vertebral column. Reason (R) is correct and directly explains why only vertebrates form this distinct subgroup within Chordata.
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