Pupil Function and difference pupil in animal eyes

 pupil - The pupil is the opening in the center of the iris.

Function of pupil - The function of the pupil is to allow light to enter the eye so it can be focused on the pupil appear perfectly round and black in color.

Q. Why is pupil black ?

ans.  Thee black color is because light that passes through the pupil is total absorbed by reflected back.

• In low light conditions - the pupil dilates so more light can reach the retina to improve night vision.
• In bright condition - pupil constricts

Generally normal pupil size in adults ranges from 2mm to 4mm in bright light to 4mm to 8mm in the dark both pupils normally constrict when you focus on a near object.

Rectangular pupil - sheep , Goats , Octopuses and Toads 

Vertical site - cats , snakes , alligators and crocodiles 

spherical - human , cow horse , ..... etc.