Given below is an example of certain structures and their special functional activities.
For example : Eye and vision, On a similar pattern complete the following:
Iris of the eye : ...............

Explanation

**Step-by-Step Solution:**

1. **Identify the Structure**: The structure we are focusing on is the "Iris of the eye."

2. **Understand the Function of the Iris**: The iris is a part of the eye that is responsible for controlling the size of the pupil.

3. **Determine the Special Functional Activity**: The special functional activity of the iris is to regulate the amount of light that enters the eye. It does this by adjusting the size of the pupil, which can dilate or constrict depending on the lighting conditions.

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