Which one of the following statements is incorrect regarding notochord.

Options

A. It is present only in larval tail in ascidian
B. It is replaced by a vertebral column in adult
C. It is absent throughout life in humans from the very beginning
D. It is present througout life in Amphioxus

Answer

To determine which statement regarding the notochord is incorrect, we will analyze each of the provided statements one by one.

### Step-by-Step Solution:

1. **Statement A: "It is present only in larval tail of Ascidian."**
- Ascidian belongs to the subphylum Urochordata. In Urochordates, the notochord is indeed present only in the larval stage, specifically in the tail.
- **Conclusion**: This statement is **correct**.

2. **Statement B: "It is replaced by a vertebral column in adult."**
- In vertebrates, the notochord is present during the embryonic stage and is replaced by the vertebral column as development progresses.
- **Conclusion**: This statement is **correct**.

3. **Statement C: "It is absent throughout life in humans."**
- This statement claims that notochord is absent in humans throughout life. However, the notochord is present during the embryonic development of humans and is later replaced by the vertebral column. Thus, it does not remain absent throughout life.
- **Conclusion**: This statement is **incorrect**.

4. **Statement D: "It is present throughout the life in amphioxus."**
- Amphioxus (also known as lancelet) is a cephalocordate where the notochord is retained throughout its life, providing structural support.
- **Conclusion**: This statement is **correct**.

### Final Answer:
The incorrect statement regarding notochord is **Statement C: "It is absent throughout life in humans."**

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