Chordata: Protochordata to Amphibia · Zoology

In Cephalochordates like Branchiostoma (Amphioxus), what is the extent of the notochord?

  1. It is restricted to the tail region only
  2. It extends from the rostrum to the tip of the tail throughout life
  3. It is replaced by a bony vertebral column during development
  4. It is present only during the embryonic stage
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Correct answer: It extends from the rostrum to the tip of the tail throughout life

Cephalochordates are unique in that the notochord extends beyond the brain into the tip of the rostrum (snout), which is why the group is named 'cephalochordate' (head-chord). Unlike vertebrates, this notochord persists as the main axial support throughout the animal's entire life.

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