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Which one of the following statements is totally wrong about the occurrence of notochord, while the other three are correct?
A
It is absent throughout life in humans from the very beginning
B
It is present throughout life in $Amphioxus$
C
It is present only in larval tail in Ascidians
D
It is replaced by a vertebral column in adult frog
Detailed Solution
The notochord is a fundamental character of all chordates; every chordate has it at least in the embryonic stage.
Humans are vertebrates: the notochord is present in the embryo and is later replaced by the vertebral column. So saying it is absent throughout life from the very beginning is totally wrong.
In $Amphioxus$ (Cephalochordata) the notochord extends from head to tail and persists throughout life – correct.
In Ascidians (Urochordata) the notochord is present only in the larval tail – correct.
In the frog, a vertebrate, the notochord is replaced by a vertebral column in the adult – correct.
Hence the wrong statement is that it is absent throughout life in humans.
Humans are vertebrates: the notochord is present in the embryo and is later replaced by the vertebral column. So saying it is absent throughout life from the very beginning is totally wrong.
In $Amphioxus$ (Cephalochordata) the notochord extends from head to tail and persists throughout life – correct.
In Ascidians (Urochordata) the notochord is present only in the larval tail – correct.
In the frog, a vertebrate, the notochord is replaced by a vertebral column in the adult – correct.
Hence the wrong statement is that it is absent throughout life in humans.