46 Vision
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 than to develop an acute sense of smell. In the course of evolution members of the primate line have acquired large eyes while the snout has shrunk to give the eye an unimpeded view. 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 however occupies only a very narrow band in the whole electromagnetic spectrum. Ultraviolet rays are invisible to humans though ants and honeybees are sensitive to them. Humans have no direct perception of infrared rays unlike the rattlesnake which has receptors tuned into wavelengths longer than 0.7 micron. The world would look eerily different if human eyes were sensitive to infrared radiation. Then instead of the darkness 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 ways. They are in fact remarkably discerning in color gradation. The color sensitivity of normal human vision is rarely surpassed even by sophisticated technical devices.
谈谈攻克雅思听力的一些窍门
过来人雅思听力经验浅谈
历年雅思听力常考学类场景词汇
雅思听力交通题:堵车的感悟
雅思听力考试需要合理安排时间
名师解读雅思听力难点及对策
雅思听力常用的30个高频短语
雅思听力技巧:雅思听力级级提高
提高雅思听力分数的五大技巧
雅思听力备考:注意精听和泛听的结合
雅思听力提高方法:灵活利用关键词
雅思听力训练技巧指导
雅思听力:如何跟上你的速度
雅思听力预测及快速提分方法
雅思听力考点解析 把握数字关键点
雅思听力考试第三问:旅游话题如何针对性备考
雅思听力备考四大注意事项
雅思听力单项选择题如何解答?
备考指导:雅思听力高分小技巧
突破雅思听力语音部分的战略步骤
雅思听力高分常见关系词总结
备考指导:五大方法提高雅思听力
雅思听力第一问:Job类话题如何备考
在生活场景中积累雅思听力词汇
解读雅思听力考试中的各数字考点
雅思听力考试机经是否有用
雅思考试听力选择题详细解析
备考指导:雅思听力审题有何作用
雅思听力辅导:比较关系
雅思听力考试之信息表填空题分析
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