[填空题]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 41 ______
course of evolution members of the primate line has acquired large 42 ______
eyes while the snout has shrunk to give the eye an unimpeding view. 43 ______
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 44 ______
electromagnetic spectrum. Ultraviolet rays are invisible to humans though
ants and honeybees are insensitive to them. Humans have no direct perception 45 ______
of infrared rays like the rattlesnake that has receptors tuned into 46 ______
wavelengths longer than 0. 7 micron. The world would look eery different 47 _