Eyes: Evolution of

Eyes detect the peak in the sun's electromagnetic radiation—light—and come in limited, convergent forms because of constraints set by the physics of light. Eyes are the sensory organs at the beginning of visual systems. A visual system such as our own, with its associated processing unit, is a complex of parts that have different functions and that are unrelated in their initial evolutionary history. A lens focuses light to form an image, retinal cells convert light waves to electrical signals, optic nerves carry those signals to the brain, the brain re-constructs the image and constructs color, and another part of the brain makes a decision about how the body will react to that image.

Eyes themselves can be classified as either chamber (or simple) or compound ...