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
外语
This section measures your ability to understand academic passages in English. The Reading section of TOEFL iBT is divided i
This section measures your ability to understand academic passages in English. The Reading section of TOEFL iBT is divided i
admin
2013-04-25
56
问题
This section measures your ability to understand academic passages in English.
The Reading section of TOEFL iBT is divided into 2 or 3 separately timed parts.
Most questions in the Reading section are worth 1 point, but the last question for each passage is worth more than 1 point. The directions for the last question include the point value of the question.
Some passages will include a word or phrase that is underlined. You can see its definition or an explanation in the Glossary box.
Within each part in the real test, you can go on to the next question by clicking the Next icon. You may skip questions and go back to them later. If you want to go back to previous questions, click the Back icon. You may click the Review icon at any time and the review screen will show you which questions you have answered and which you have not. From the review screen, you can go directly to any question you have already seen in the Reading section.
You will now begin the Reading section. There is 1 passage for this part of the section, and you will have 20 minutes to read the passage and answer the questions.
Natural Selection
First coined by Darwin, the term natural selection refers to the process at the core of evolutionary theory. Simply put, Darwin believed that every living organism had to struggle to survive and reproduce. By random chance, some individuals in a species would have characteristics that made them better adapted to this struggle than their contemporaries. Such individuals would be more likely to reproduce and pass their characteristics on to their offspring. Over many generations, a series of small differences in characteristics would accumulate, until eventually the creatures that were produced would be so different from their original ancestors that they would constitute a new species.
(A) Although Darwin did not know how variations between individual members of the same species were able to arise in the first place or how such traits could then be passed on from species to species, we now know that this process occurs through genes.
(B) Genes determine what characteristics an organism will possess, from its size to its skin color to its gender.
(C) Sometimes these genes become damaged or altered--a process known as mutation.
(D) Most mutations are either too small to have any effect, or have detrimental effects on the organism. A few, however, can be beneficial to helping an organism survive. The organisms with these beneficial mutations are the ones that .survive and reproduce, passing their particular genetic mutation on to future generations.
Originally, Darwin thought that two particular types of traits were naturally selected for evolution. The first type included any and all traits that helped an organism survive, either by giving it easier access to food, better protection from predators, or superior adaptability to shifting environmental conditions. Several examples of the natural selection of such traits have been observed since Darwin first proposed his theory. The most often cited example is the coloration of moths near industrial centers. Some of them have white wings and the others have black wings. Under normal conditions, the lighter-colored moths predominate since white moths are less visible against the light-colored bark of the trees in the forests where they live, which means they can more easily avoid predators. Near industrial centers, however, darker-colored moths predominate, as the pollution from the factory has darkened the bark of the nearby trees. Moths landing on these trees are much more difficult to see if they have black wings. This trait has now become most common in moth populations living in areas where pollutants have changed the color of the tree bark.
The second type of naturally selected traits envisioned by Darwin involved those characteristics of an organism that made it easier for that organism to find a mate. This form of natural selection, often called sexual selection, was thought to explain the existence of highly developed traits in certain animals that seemed to play no particular role in their survival, and that in some cases seemed to make it even harder for them to survive. A prime example of such a trait is the peacock’s elaborate, colorful tail feathers. A long, unwieldy tail that can expand into a display of bright colors that draws the attention of any predator in the vicinity seems less likely than that of other kinds of birds to help the bird survive. However, researchers discovered that peahens invariably chose to mate with those peacocks whose tail feathers produced the most artistic displays. Thus, although the peacock’s tail feathers have no adaptive function in terms of coping with survival pressure, the gene that controls feather color is the one that is most likely to be passed on because of its role in the mating process.
Many scientists now believe that a third type of naturally selected characteristics exists, namely those that may be harmful to an individual organism but beneficial to that organism’s species. This helps to explain the persistence of certain traits that were viewed under traditional evolutionary theory as not assisting in adaptation. For instance, in many animal species, including humans, a small subset of the population is homosexual. Under the old view of evolution, this could not be accounted for since homosexual individuals do not normally reproduce, meaning the gene that codes for it should have long been phased out of the gene pool. However, recent studies among wild sheep populations have found that the prevalence of homosexuality in the sheep population increases in times of severe food shortages, causing the sheep to form stronger bonds with sheep of the same sex than they otherwise would. As a result, instead of fighting over a particular food source, these sheep share the food they find with each other, increasing the species’ chance of surviving hard times. Though still controversial, the idea that traits may be naturally selected because of their benefits to the species instead of their benefits to the individual is rapidly gaining acceptance in the scientific community because of the wide array of characteristics that it can explain, including the human tendency towards altruism
The word "particular" in the passage is closest in meaning to
选项
A、exacting.
B、noteworthy.
C、precise.
D、specifi
答案
D
解析
词汇题 particular的意思是“特定的”、“特别的”,选项中与其意义相近的是specific(特定的)。
转载请注明原文地址:https://kaotiyun.com/show/97yO777K
0
托福(TOEFL)
相关试题推荐
Completethesummarybelow.UseNOMORETHANTHREEWORDSforeachanswer.PROJECTMANAGENTLastweek’sdefinitionofpro
CompletethefollowingnotesusingNOMORETHANTHREEWORDSforeachanswerIfrobbed,youshouldcontactyour【16】orDarling
Completethenotesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.ResearchTopic-InstantMessagingaddictio
Completethenotesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.ResearchTopic-InstantMessagingaddictio
Completethenotesbelow.WriteNOMORETHANTHREEWORDSforeachanswer.ResearchTopic-InstantMessagingaddictio
SECTION3Questions21-30Questions21-25AnswerthefollowingquestionsusingNOMORETHANTHREEWORDSAND/ORNUMBERSforeac
CompletethenotesbelowbywritingNOMORETHANTHREEWORDSinthespacesprovided.TheGovernmentplanstogive【T14】$______to
Whichgroupgavethefollowingadvice?TickColumnAifitwasmainlywomen.TickColumnBifitwasmainlymen.TickColumnCi
Choosethecorrectletter,A,BorC.WinridgeForestRailwayParkWhentheystarted,thefamilydecidedto
Choosethecorrectletter,A,BorC.CourseFeedbackWhatdoesSpirosthinkofhisreadingskills?
随机试题
下列各组词语中,存在错别字的有()。
________的关键就在于企业要不断地进取创新,提升产品的质量,并不断开发系列新产品,使得竞争对手无力招架,无法应对。()
省级以上药品监督管理部门根据实际情况建立监控信息网络实时监控麻醉药品和精神药品定点生产企业、定点批发企业和使用单位的下列哪些活动
黄连配吴茱萸可治
什么是无纸通关?
房产税的纳税义务人为()或者使用人。
甲公司2017年1月1日售出大型设备一套,协议约定采用分期收款方式,从销售当年年末开始分5年分期收款,每年收取1000万元,合计5000万元,成本为3000万元。不考虑增值税等相关税费的影响。假定销货方在销售成立日应收金额的公允价值为4000万元,实际利率
【2015年】下列有关抽样风险的说法中,错误的是()。
下图为我国西部某省人口数据统计图。近年全国人口自然增长率为0.5%左右。据此回答下列问题。关于该省人口状况的叙述,正确的是()。
Americansdependontheircarsmorethananyotherpeople.Thefamilycarhasbeenacommonthingsincetheearly20thcenturya
最新回复
(
0
)