首页
登录
职称英语
The human criterion for perfect vision is 20/20 for reading the standard lin
The human criterion for perfect vision is 20/20 for reading the standard lin
游客
2023-09-04
37
管理
问题
The human criterion for perfect vision is 20/20 for reading the standard lines on a Snellen eye chart without a hitch. The score is determined by how well you read lines of letters of different sizes from 20 feet away. But being able to read the bottom line on the eye chart does not approximate perfection as far as other species are concerned. Most birds would consider us very visually handicapped. The hawk, for instance, has such sharp eyes that it can spot a dime on the sidewalk while perched on top of the Empire State Building. It can make fine visual distinctions because it is blessed with one million cones (视锥细胞) per square millimeter in its retina (视网膜). And in water, humans are farsighted, while the kingfisher, swooping down to spear fish, can see well in both the air and water because it is endowed with two foveae (凹窝)-areas of the eye, consisting mostly of cones, that provide visual distinctions. One fovea permits the bird, while in the air, to scan the water below with one eye at a time. This is called monocular vision. Once it hits the water, the other fovea joins in, allowing the kingfisher to focus both eyes, like binoculars, on its prey at the same time. A frog’s vision is distinguished by its ability to perceive things as a constant motion picture. Known as "bug detectors", a highly developed set of cells in a frog’s eyes responds mainly to moving objects. So, it is said that a frog sitting in a field of dead bugs wouldn’t see them as food and would starve.
The bee has a "compound" eye, which is used for navigation. It has 15,000 facets that divide what it sees into a pattern of dots, or mosaic. With this kind of vision, the bee sees the sun only as a single dot, a constant point of reference. Thus, the eye is a superb navigational instrument that constantly measures the angle of its line of flight in relation to the sun. A bee’s eye also gauges flight speed. And if that is not enough to leave our 20/20 "perfect vision" paling into insignificance, the bee is capable of seeing something we "can’t—ultraviolet light. Thus, what humans consider to be "perfect vision" is in fact rather limited when we look at other species. However, there is still much to be said for the human eye. Of all the mammals, only humans and some primates can enjoy the pleasures of color vision. [br] A bee finds its direction by_____.
选项
A、dividing what it sees into thousands of dots
B、constantly gauging its flying speed
C、using the sun as a constant point of reference
D、measuring the angle of the sun
答案
C
解析
第2段第3、4句描述了蜜蜂利用太阳导航的机制,据此可知C正确。
转载请注明原文地址:https://tihaiku.com/zcyy/2984297.html
相关试题推荐
PartⅡReadingComprehension(SkimmingandScanning)Directions:Inthispart,y
PartⅡReadingComprehension(SkimmingandScanning)Directions:Inthispart,y
PartⅡReadingComprehension(SkimmingandScanning)Directions:Inthispart,y
PartⅡReadingComprehension(SkimmingandScanning)Directions:Inthispart,y
PartⅡReadingComprehension(SkimmingandScanning)Directions:Inthispart,y
PartⅡReadingComprehension(SkimmingandScanning)Directions:Inthispart,y
PartⅡReadingComprehension(SkimmingandScanning)Directions:Inthispart,y
PartⅡReadingComprehension(SkimmingandScanning)Directions:Inthispart,y
WhenToyotaMotorCorp.movedoneofitsdivisionsintoanenvironmentallyfr
WhenToyotaMotorCorp.movedoneofitsdivisionsintoanenvironmentallyfr
随机试题
Thispartistotestyourabilitytodopracticalwriting.Youarerequiredtow
泰罗科学管理所要解决的中心问题是()。A.提高劳动效率 B.资源配置 C.
A. B. C. D.肾小球滤过率降低 E.
关于项目风险的描述,不正确的( )。A.已知风险与未知风险都可以进行管理 B
下列各项中,()是一种法定的垄断权,其他企业及个人未经专利权人的许可,不能
男,29岁,高处坠落2小时后送至医院,主诉腰背部疼痛,双下肢不能活动经正确的治疗
简述现代企业人力资源管理各个历史发展阶段的特点。
会议决定,《城市生活无着的流浪乞讨人员救助管理办法(草案)》经进一步修改后,国务
下列关于保险诈骗罪的说法,正确的有( )。A.侵犯的客体是复杂客体,既侵犯了国
甲企业是一家跨国公司,为了进入A国市场,其与A国本地的乙公司结成合作关系,形成战
最新回复
(
0
)