Notochord is converted to _________in the adult stage.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Notochord**: The notochord is a flexible rod-like structure found in the embryos of all chordates. It serves as a primary support structure during the early stages of development.

2. **Developmental Changes**: As the organism matures, particularly in vertebrates, the notochord undergoes transformation. In many species, it is replaced by a more complex structure.

3. **Formation of the Vertebral Column**: In adult vertebrates, the notochord is converted into the vertebral column (also known as the backbone or spine). The vertebral column is made up of individual vertebrae that provide a rigid structure for support and protection.

...