Touch Receptors can adapt to a stimulus - put an ear ring on pretty soon you don't know it is there. Light comes through the pupil. When examining something close, the cillary muscle are contacted relaxing the zonular fibers which allows the lens to become more spherical. Optic disk - blind spot where optic nerves comes through retina no rods or cones. Each photopigment is bound to a chomophobe molecule called retinal, a Vit.
Most domestic animals have limited color vision.
Colors are a blend of these 3 pigment being stimulated - like mixing colors. If you tried to catch 50,000 broilers in a chicken house when it is light you would probably hurt or kill the majority of them. Makes it tough to read a stop light. Carnivores have more binocular vision - need to see where dinner is at in order to catch. Herbivores have more peripheral vision - seeing with only one eye a good part of the time.