In which sub-phylum Notochord extends from head to tail region and persistent throughout their life?

Options

A. Cephalochordata
B. Urochordata
C. Both (A) and (B)
D. none of the above

Answer

To answer the question, "In which sub-phylum does the notochord extend from head to tail region and persist throughout their life?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Phylum Chordata**:
- The phylum Chordata is characterized by the presence of a notochord at some stage of development. The notochord is a flexible rod-like structure that provides support.

2. **Identifying Sub-phyla of Chordata**:
- The phylum Chordata is divided into three main subphyla:
- Urochordata (or Tunicates)
- Cephalochordata
- Vertebrata

3. **Analyzing Urochordata**:
- In Urochordata, the notochord is present only in the larval stage and is restricted to the tail region. It does not persist throughout the organism's life.

4. **Analyzing Cephalochordata**:
- In Cephalochordata, the notochord extends from the head to the tail region and persists throughout the life of the organism. This means that the notochord remains a significant structure for support throughout their entire life cycle.

5. **Conclusion**:
- Based on the analysis, the sub-phylum in which the notochord extends from head to tail and persists throughout life is **Cephalochordata**.

### Final Answer:
The answer to the question is **Cephalochordata**.

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