Which one of the following structure is present in all adult vertebrates?

Options

A. Notochord
B. Dorsal tubular nerve cord
C. Pharyngeal gill slits
D. Renal portal system

Answer

To determine which structure is present in all adult vertebrates, we can analyze the options provided:

1. **Notochord**:
- The notochord is a flexible rod-like structure that is present in the embryonic stages of all chordates. However, in most adult vertebrates, it is replaced by the vertebral column (spine). Therefore, this option is incorrect for adult vertebrates.

2. **Dorsal Tubular Nerve Cord**:
- The dorsal tubular nerve cord is a hollow structure that runs along the back of the organism. It is a defining characteristic of chordates and is present in all adult vertebrates. This option is correct.

3. **Pharyngeal Gill Slit**:
- Pharyngeal gill slits are structures that are present during the embryonic stages of many vertebrates, but they do not persist in all adult forms. In many adult vertebrates, these structures are either modified or absent. Thus, this option is also incorrect.

4. **Renal Portal System**:
- The renal portal system is a feature found in some vertebrates, particularly in certain groups of fish and amphibians, but it is not universally present in all adult vertebrates. Therefore, this option is incorrect.

Based on the analysis of the options, the only structure that is present in all adult vertebrates is the **dorsal tubular nerve cord**.

**Final Answer**: The structure present in all adult vertebrates is the **dorsal tubular nerve cord**.

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