Human vision like that of other primates has evolved in an arborealenvironment. In the den
Human vision like that of other primates has evolved in an arboreal
environment. In the dense complex world of a tropical forest, it is more
important to see well to develop an acute sense of smell. In the 【M1】______
course of evolution members of the primate line has acquired large 【M2】______
eyes while the snout has shrunk to give the eye an unimpeding view. 【M3】______
Of mammals only humans and some primates enjoy color vision. The red
flag is black to the bull. Horses live in a monochrome world. Light visible to
human eyes, therefore, occupies only a very narrow band in the whole 【M4】______
electromagnetic spectrum. Ultraviolet rays are invisible to humans though
ants and honeybees are insensitive to them. Humans have no direct perception 【M5】______
of infrared rays like the rattlesnake that has receptors tuned into 【M6】______
wavelengths longer than 0. 7 micron. The world would look eery different 【M7】______
if human eyes are sensitive to infrared radiation. Then instead of the darkness 【M8】______
of night, we would be able to move easily in a strange shadowless world
where objects glowed with varying degrees of intensity. But human eyes excel
in other way. They are in fact remarkably discerning in color gradation. 【M9】______
The color sensitivity of normal human vision is rarely surpassed even 【M10】______
sophisticated technical devices.
【M1】