Vertebrates differ from other chordates in having ....... replaced in adults by a ......

Explanation

To solve the question "Vertebrates differ from other chordates in having ....... replaced in adults by a ......", we can follow these steps:

### Step 1: Understand the Key Terms
- **Vertebrates**: These are animals that have a backbone or spinal column.
- **Chordates**: This is a broader category that includes all animals with a notochord at some stage of their development.

### Step 2: Identify the Structure Present in Chordates
- In all chordates, there is a structure known as the **notochord**. This is a flexible rod that provides support during the embryonic stage.
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