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
35
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 conditions does the passage suggest is a possible cause for the failure of a lobster to develop a crusher claw?
选项
A、The loss of a claw during the third or earlier stage of development.
B、The lose of claw during the fourth or fifth stage of development.
C、The loss of a claw during the sixth stage of development.
D、Development in an environment devoid of material that can be manipulated.
答案
D
解析
本题的四个选项中,只有D项为正确答案。这可从文中的最后两句话“Incontrast,when juvenile lobsters were reared in a smooth tank without the oyster chips,the majority developed two cutter claws.This unusual configuration of symmetrical cutterclaws did not change when the lobsters were subsequently placed in a manipulable environment or when they lost and regenerated one or both claws.”推知,即在没有可以操作的对象的环境中长大的龙虾是不会长出crusher claw的。
转载请注明原文地址:https://kaotiyun.com/show/rDTO777K
0
考博英语
相关试题推荐
Recentresearchfromanimalbehavioristssuggeststhat"asthecrowflies"shouldnolongerbetakentomean"theshortestdista
It’snevereasyforamightymilitarytotreadlightlyonforeignsoil.InthecaseofAmericanforcesinSouthKorea,protector
"Before,weweretooblacktobewhite.Now,we’retoowhitetobeblack."Hadija,oneofSouthAfrica’s3.5mColoured(mixedr
Buildingthisroadwill______theconstructionoftenbridges,andthenthetotalcostreaches1millionUSdollars.
Thefundisfor______distressamongthefloodvictimsinthesoutherncity.
TheFreedomofInformationActgivesprivatecitizen______governmentfiles.
Thetwodelegateshadanin-depthexchangeofviewsonhowtoenhancetheir______cooperation.(2002年中国人民大学考博试题)
WhenPh.Dcandidates______theirimpendingprofessorships,theyconsiderhousingbenefitsofferedbytheprospectiveuniversiti
Apoliceofficerwassentto______thecrime.
AIDSiscausinggreatpublicconcernbecausethe______fataldiseasehitsprimarilyyoungpeople.(2002年中国人民大学考博试题)
随机试题
解热镇痛抗炎药的解热作用机制为
初产妇,28岁,孕41周,阵发性腹痛6小时阴道流液2小时,骨盆外测量出口横径7.5cm,余正常,枕右前位,胎心140次/分,肛诊宫口扩张6cm,先露+1,3小时后宫口开全,先露+2,宫缩40~50秒/2~3分钟,观察2小时无进展。
患者,男,65岁。慢性咳嗽、喘息史15年,近日感冒后症状加重。查体:神志清楚,口唇发绀,桶状胸,双肺叩诊过清音,呼吸音减低,动脉血气分析:PaO250mmHg,PaCO265mmHg,经治疗后病情缓解。该患者出院后,不适宜的治疗是
按资金来源划分,个人住房贷款可分为()。
在隧道施工测量中,隧道永久中线点应在竣工测量后用()包埋金属标志。
对危险房的处理措施有()。
一列火车通过一条长1140米的桥梁(车头上桥至车尾离桥)用50秒,火车穿越长1980米的隧道用80秒,则这列火车车身是()米。
考虑如下价格指数问题。一个只有3种商品进入CPI(消费价格指数)的简单经济,这三种商品是食品、住房和娱乐。假定居民在基年(1987年)以当时的价格消费如下表5.6所示:定义消费价格指数CPI。
理想与现实本来就是一对矛盾,二者是对立统一的关系。其中,统一性体现在()。
Aweathermapisanimportanttoolforgeographers.Asuccessionofthreeoffourmapspresentsacontinuouspictureofweather
最新回复
(
0
)