Question

Notochord persists throughout life in:

• A. Petromyzon
• B. Fish
• C. Frog
• D. Latimeria

Hint:

Lampreys and hagfish are unique among vertebrates for retaining a notochord throughout their life.

Answer 1

The Correct Option is A

Step 1: The notochord is a flexible, rod-shaped structure that provides support to the body in early development in chordates. In many chordates, the notochord is replaced by the vertebral column (backbone) during development. 
Step 2: In the case of Petromyzon (the lamprey, a type of jawless fish), the notochord persists throughout the organism's life. Lampreys are a part of the group called agnathans, and unlike most vertebrates, they retain the notochord as the primary structure for support throughout their life. |
Step 3: In most fish (Option 2), the notochord is replaced by the vertebral column as the animal matures, so it does not persist throughout life. 
Step 4: In frogs (Option 3), the notochord is replaced by the vertebral column during early development, so it does not persist throughout life. 
Step 5: In Latimeria (Option 4), also known as the coelacanth, the notochord is replaced by the vertebral column as development progresses, so it does not persist throughout life. 
Conclusion: The notochord persists throughout life only in Petromyzon.