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
The two claws of the mature American lobster are decidedly different from each other. The crusher claw is short and stout; the c
The two claws of the mature American lobster are decidedly different from each other. The crusher claw is short and stout; the c
admin
2021-06-15
44
问题
The two claws of the mature American lobster are decidedly different from each other. The crusher claw is short and stout; the cutter claw is long and slender. Such bilateral asymmetry, in which the fight side of the body is, in all other respects, a mirror image of the left side, is not unlike handedness in humans. But where the majority of humans are right-handed, in lobsters the crasher claw appears with equal probability on either the right side or left side of the body.
Bilateral asymmetry of the claws comes about gradually. In the juvenile fourth and fifth stages of development, the paired claws are symmetrical and cutter like. Asymmetry begins to appear in the juvenile sixth stage of development, and the paired claws further diverge toward well-defined cutter and crusher claws during succeeding stages. An intriguing aspect of this development was discovered by Victor Emmer. He found that if one of the paired claws is removed during the fourth or fifth stage, the intact claw invariably becomes a crusher, while the regenerated claw becomes a cutter. Removal of a claw during a later juvenile stage or during adulthood, when asymmetry is present, does not alter the asymmetry; the intact and regenerate claws retain their original structures.
These observations indicate that the conditions that trigger differentiation must operate in a random manner when the paired claws are intact, but in a nonrandom manner when one of the claws is lost. One possible explanation is that differential use of the claws determines their asymmetry. Perhaps the claw that is used more becomes the crusher. This would explain why, when one of the claws is missing during the fourth or fifth stage, the intact claw always becomes a crusher. With two intact claws, initial use of one claw might prompt the animal to use it more than the other throughout the juvenile fourth and fifth stages, causing it to become a crusher.
To test this hypothesis, researchers raised lobsters in the juvenile fourth and fifth stages of development in a laboratory environment in which the lobsters could manipulate oyster chips.(Not coincidentally, at this stage of development lobsters typically change from a habitat where they drift passively, to the ocean floor where they have the opportunity to be more active by borrowing in the substrate.)Under these conditions, the lobsters developed asymmetric claws, half with crusher claws on the left, and half with crusher claws on the right. In contrast, when juvenile lobsters were reared in a smooth tank without the oyster chips, the majority developed two cutter claws. This unusual configuration of symmetrical cutter claws did not change when the lobsters were subsequently placed in a ma-nipulable environment or when they lost and regenerated one or both claws.
Which of the following experimental results, if observed, would most clearly contradict the findings of Victor Emmer?
选项
A、A left cutter like claw is removed in the fifth stage and a crusher claw develops on the right side.
B、A left cutter like claw is removed in the fourth stage and a crusher claw develops on the left side.
C、A left cutter like claw is removed in the six stage and a crusher claw develops on the right side.
D、A left cutter like claw is removed in the fourth stage and a crusher claw develops on the right side.
答案
B
解析
本题的四个选项中,只有B项为正确答案。这可从文中的内容推知,即Victor Emmer的发现是:如果在龙虾生长的第四或第五期弄掉它只螯的话,那么完好的那只螯就会成为crusher claw,而再生的就会成为cutter claw。但如果这发生在这生长期之后,那么龙虾的已有结构就不会改变了。
转载请注明原文地址:https://kaotiyun.com/show/MDTO777K
0
考博英语
相关试题推荐
Recentresearchfromanimalbehavioristssuggeststhat"asthecrowflies"shouldnolongerbetakentomean"theshortestdista
The______of"snake"issimplythis:aleglessreptilewithalong,thinbody.
Althoughtheaccidentdidverylittle______tothecar,Istillsuggestthatyoudrivemorecarefullynexttime.
Forsomeonewhoselifehasbeenshattered,HiroshiShimizuisremarkablycalm.InacrampedTokyolawoffice,thesubdued,bitte
Thebasicreasonfortheexistenceofmulti-nationalcompaniesisthecompetitiveadvantageofaglobalnetworkofproductionan
Cananimalshaveasenseofhumor?SallyBlanchard,publisherofanewslettercalledthePetBirdReport,thinksapetparrotma
Aknowledgeofhistory______ustodealwiththevastrangeofproblemsconfrontingthecontemporaryworld.(2007年中国人民大学考博试题)
Apoliceofficerwassentto______thecrime.
PresidentJimmyCarterinturnagreedtotrytoreduceAmericanoilimportsandstem______intheUnitedStates.
Itisreportedthatmentalhealthhasbecomeatroublesomeissue.Thenumberofpeoplecommittingsuicideisontherise.Youar
随机试题
A.地尔硫B.硝苯地平C.氢氯噻嗪D.贝那普利E.美托洛尔高血压伴痛风的患者降压不宜选用
掌握知识是智力发展的基础,因此掌握的知识越多,智力发展水平就越高。()
为什么说“口语第一性,书面语第二性”。
注册会计师B在对应收账款进行审计时,选取的函证对象为( )。下列有关对应收账款函匪的提法错误的有( )。
2012年7月1日起实施的《党政机关公文格式》规定,公文中成文日期用阿拉伯数字将年、月、日标全。()
水是万物本原的观点属于()。
面对“两会”:代表,委员的依法______,有的官员虽然还不能圆满______,但都表现出虚心接受、认真反思的态度。填入横线部分最恰当的一项是()。
ThebeginningofAmericanliteratureAmericanhasalwaysbeenalandofbeginnings.AfterEuropeans"discovered"Americain
Toclaimsupernaturalpowersandthenbecaughtindirtyacts—sexuallyabusingchildrenor,evenworse,protectingtheabusers—i
A、Bykeepingtheproblemsbyherself.B、Bygoingdirectlytothebosswithherproblems.C、Bytellingherboss’smotheraboutth
最新回复
(
0
)