首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
专升本
Bacteria(细菌)are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measur
Bacteria(细菌)are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measur
admin
2015-10-30
20
问题
Bacteria(细菌)are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial size is measured in microns. One micron is a thousandth of a millimeter; a pinhead is about a millimeter across. Rod-shaped bacteria are usually from two to four microns long, while rounded ones are generally one micron in diameter. Thus, if you enlarged a rounded bacterium a thousand times, it would be just about the size of a pinhead. An adult human magnified by the same amount would be over a mile(1. 6 kilometers)tall.
Even with an ordinary microscope, you must look closely to see bacteria. Using a magnification of 100 times, one finds that bacteria are barely visible as tiny rods or dots. One cannot make out anything of their structure. Using special stains, one can see that some bacteria have attached to them wavy-looking "hairs" called flagella. Others have only one flagellum. The flagella rotate, pushing the bacteria through the water. Many bacteria lack flagella and cannot move about by their own power, while others can glide along over surfaces by some little-understood mechanism.
From the bacterial point of view the world is a very different place from what it is to humans. To a bacterium water is as thick as molasses(糖蜜)is to us. Bacteria are so small that they are influenced by the movements of the chemical molecules around them. Bacteria under the microscope even those with no flagella often bounce about in the water. This is because they collide with the water molecules and are pushed this way and that molecules move so rapidly that within a tenth of a second the molecules around a flagellum have been replaced by new ones. Even bacteria without flagella are thus constantly exposed to a changing environment.
The relationship between a bacterium and its flagella is most nearly analogous to which of the following?
选项
A、A rider jumping on a horse’s back.
B、A ball being hit by a bat.
C、A boat powered by a motor.
D、A door closed by a gust of wind.
答案
C
解析
转载请注明原文地址:https://kaotiyun.com/show/yfYC777K
本试题收录于:
英语题库成考专升本分类
0
英语
成考专升本
相关试题推荐
Inordertolearnaforeignlanguagewell,itisnecessarytoovercomethefearofmakingmistakes.Iftheprimarygoal(目标)of
OnthemorningofNovember18,1735,anearthquakeshookBoston,Massachusetts.JohnWinthrop,aprofessoratHarvardCollege,fe
Wildandfarmbirdsoftengetafluvirus.Yettheyusuallyareabletocarrytheviruswithoutgettingsick.In1997sixpe
Ihadjustgonetobedafteraveryharddaywhenthephonerang.Itwasaneccentric(怪癖)farmer.Ihadnevermethimbeforealt
OldJapaneselivingalonecannowhirea"family"forlunchandafewhours’pleasanttalk.Justgivethemaringandaskfor,sa
You______yesterdayifyouwerereallyseriousaboutthejob.
AirportbaggagescreenersintheUSA,displayingseizedchainsaws,machetesandknives,【21】travelerstochecktheirluggagefor
Ontelevisionallovertheworldthereareprogrammesabouttheworkofthepolice.Theyarepopularbecausetheyareusuallyve
Asprotectorofherfamily’shealth,thepoineerwomanconfrontedsituationssheneverimaginedbeforecrossingtheMississippi.
Notallpeoplegottheirnames【21】theirfathers.Somegottheirnamesfromtheplacesthey【22】.Forexample,afamilyhadlived
随机试题
下列句中的修辞手法运用不恰当的一项是()。
答问的技巧包括()
正常小儿,体重8kg,身长68cm,前囟1cm,有乳牙3颗。其可能达到的发育水平是()。
A.芍药、桂枝B.炙甘草C.生姜D.大枣E.饴糖
腰椎椎体不易除外骨破坏病变时需查()
“直客式”运行模式是指由购车人首先到经销商处挑选车辆,然后通过经销商的推荐到合作银行办理贷款手续。()
打开考生文件夹下的演示文稿yswg.pptx,按照下列要求完成对此文稿的修饰并保存。为整个演示文稿应用“风舞九天”主题,全部幻灯片切换方案为“华丽型”、“库”,效果选项为“自左侧”。
Theoutlookfromthetopofthemountainisbreathtaking.
TodaytherearethreedifferentkindsofNewYorkers:thepeoplewhoactasiftheywerebornhere:thepeoplewhoarehereand
•Readtheintroductionbelowaboutaconference.•ChoosethebestwordtofilleachgapfromA,B,CorDontheoppositepage.
最新回复
(
0
)