Here's a breakdown:
* Pupils are openings in the iris, the colored part of the eye.
* Light enters the eye through the pupil.
* The iris controls the size of the pupil, regulating the amount of light entering the eye.
Why is this important?
* In bright light, the pupil constricts to prevent too much light from entering, which can damage the retina.
* In dim light, the pupil dilates to let in more light, improving vision in low-light conditions.
Dogs, in particular, have pupils that are shaped like slits. This shape helps them to:
* See better in low light: The slit shape allows more light to enter the eye when it's dark.
* See more clearly at a distance: The slit shape helps to focus light on the retina for sharper vision.
So, in short, dogs have pupils to let in light, and the shape of their pupils is an adaptation that allows them to see better in different lighting conditions.