Animal eyes have one big job in common, and that’s to collect light.
Animals, including you, must collect light so they can see. No animal can see in total darkness—not even a cat, as some people think.
Animal eyes have many of the same basic parts for collecting light. First, they need a hole, or pupil, to let in the light. They also need a lens to focus it. Without a lens, images would be very fuzzy. Finally, eyes have a retina (RET-ih-na)—a bit like a movie screen—where the light is projected. Chemicals in the retina change the light images into nerve signals that the brain can understand.
We know what parts animal eyes have in common, but what makes them different?
