Which one of the following statements is totally wrong about the occurrence of notochord, while the other…
Which one of the following statements is totally wrong about the occurrence of notochord, while the other three are correct?
It is present only in larval tail in Ascidians
It is replaced by a vertebral column in adult frog
It is absent throughout life in humans from the very beginning
It is present throughout life in Amphioxus
Solution
The notochord is a flexible, rod-shaped body found in embryo of all chordates. It is composed of cells derived from the mesoderm. It represents the primitive axis of embryo. In some chordates, it persists throughout life as the main axial support of the body (e.g., Amphibians), while in most vertebrates including humans it becomes the vertebral body of the vertebral column.