what on earth books EYE SPY Wild Ways Animals See the World GUILLAUME DUPRAT
CONTENTS Reptiles amphibians worms and mollusks How do we see Mammals Birds Insects Glossary Index List of sources 3 7 17 23 29 34 34 35
HOW DO WE SEE Below is a scene viewed through human eyes But what about the other animals in the picture Do they see the same thing Some animals have a wide field of vision but others have a narrow one Some see fast movements and others can only perceive motion when it’s slow Some animals see the world in many colors others only see one or two Some can make out lots of detail others move through a world of fuzzy shapes Look out for the symbols below to learn more about how animals see Field of vision How much of their surroundings animals see depends on where their eyes are on their heads Light and color When light enters our eyes it hits the surface at the back of the eyeball This surface the retina is Predators such as tigers and wolves have eyes that face forward They see very well in front of them Prey animals such as deer and cows have eyes on the sides of their heads They see much better what’s around them keeping a lookout for hungry predators 180 degrees 360 degrees Humans have a field of vision of 200 degrees This means we see just over half of the circle around us This system allowed our ancestors to spot danger to the sides Our vision has three areas In the one on each side we see with only one eye But in the area in the center we see with both eyes at once called binocular vision In this zone we see objects in 3-D and judge distances best Capturing movement To see movement our eyes take still snapshots Then our brain puts them together to make a sequence Humans take about twenty of these snapshots per second But some animals take as few as four snapshots per second This means they can only see much slower movements than we do Others take as many as 300 They can see movements so fast that they are invisible or very blurry to us covered in special cells that capture light There are two types of these cells called rods and cones Rod cells only detect light’s brightness But cone cells detect wavelengths of light and convert them to colors We are used to the rainbow of colors we see but many animals cone cells are different from ours This means some see fewer colors than we do Others see lots more including ultraviolet and infrared ultraviolet violet blue green yellow orange red infrared invisible to humans colors visible to humans invisible to humans Sharp or blurry Some animals can see in sharp focus Others travel through a blurry world For most animals in this book sharpness depends on three things the size of the eye the shape of the lens that focuses light and the number of rod and cone cells on the back of the eye
