28 Incredible Eyes-Low

Incredible Eyes FOCUS Question How do eyes help animals survive?

Why Eyes? If you look at your eyes in the mirror, you will see the pupil and the iris. The pupil is the dark hole in the center. The iris is the colored part. These two parts work together to let light into the eye. Have you tried to take a photo in a dark room? The picture will look better if you use a flash. Light from the flash reflects off the items in the room. Reflected light enters the camera and the camera records the image. Animal eyes do something similar. They take in reflected light and the brain makes sense of the image.

How the Eye Works When reflected light enters the eye, it passes through the cornea, a thin, clear covering. Next, the light goes into the pupil. Eye muscles on the iris control the pupil by making it larger or smaller. This lets in more or less light. The lens is the curved structure in your eye. that bends light to focus an image onto the back of the eye. In the back of the eye is the retina. The image that forms there is actually upside down! The brain fixes this and flips the image to make it right-side-up.

Roses Are Red What makes a green leaf look green? The answer begins with understanding sunlight. You can make a rainbow with a prism, which separates the Sun's white light into the many colors we see. When sunlight hits a leaf, some light is absorbed and some is reflected. A green leaf absorbs all the colors of light except green. The reflected green light is the color you see. Your eye has small cells in the retina called cones that respond to different colors of light. When you see green, the cones that react to the color green send signals to your brain. Your brain processes that information and tells you that you are seeing green. Do You Know? Some animals such as snakes, vampire bats and bedbugs can "see" heat. One form of heat is infrared light. which is outside the spectrum of light that humans can see.

Seeing in the Dark Unlike people, cats are most active at night. How do they see in the dark? Cats have a shiny, reflective surface inside their eyes. This surface reflects light onto the retina to help cats see in the dark. At night, their pupils open up to let in more light. Other nocturnal animals, like deer, have similar eyes. Deep-sea animals like the giant squid and the octopus live in darkness. They have some of the largest eyes of all animals. Large eyes can let more light in to help these animals see in the dark.

Eat or Be Eaten One of the biggest reasons animals need vision is to be able to hunt for food and to avoid being hunted. Animals that hunt are called predators and the animals they eat are called prey. Most predators, including owls, have eyes on the front of their heads. This lets them focus both eyes forward, giving them stereoscopic (STEH-ree-oh-SKOP-ick) vision. Their two eyes create a single image. This ability helps animals tell how far away an object is. Try covering one eye. It's hard to figure out how near or far something is without stereoscopic vision. The owl's prey, a squirrel, has eyes on the sides of its head. This allows the squirrel to spot predators on all sides without moving around and risking getting noticed.