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
20
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
"Before,weweretooblacktobewhite.Now,we’retoowhitetobeblack."Hadija,oneofSouthAfrica’s3.5mColoured(mixedr
AsApplepreparestoreportwhat(analystsproject)maybethecompany’sfirstyear-over-yearquarterlyearningsdeclineinadeca
Don’tcallhimjustacollegeprofessor.Internetentrepreneur,TVpersonality,advisortopresidents,andfriendtotherichan
Don’tcallhimjustacollegeprofessor.Internetentrepreneur,TVpersonality,advisortopresidents,andfriendtotherichan
ManyEuropeans______theContinentofAfricainthe19thcentury.
Apoliceofficerwassentto______thecrime.
TheInternet,E-commerceandglobalizationaremakinganeweconomicerapossible.Inthefuture,capitalistmarketswilllargel
随机试题
金属切削机床应通过设计尽可能排除或减少所有潜在的危险因素,通过设计不能避免或充分限制的危险,应采取必要的安全防护装置。下列关于防止机械危险安全措施的说法中。正确的是()。
患者,男,30岁。急起发热,伴头痛乏力。体查:体温39℃,血压75/60mmHg,球结膜充血,颜面及胸前皮肤潮红,肝于肋下1cm触及,血常规:WBC25×109/L,N0.83,L0.14,PLT61.1×109/L,尿蛋白(+++)。本病例的诊
脾为气血生化之源的理论基础是
苏某为庆祝其喜得贵子,邀请胡某等到酒店聚餐。苏某从顾某处购得一超大海螺,将海螺带到酒店交给厨师时,从中剖得一颗硕大的橙黄色椭圆形珍珠,市值1万元。关于该珍珠的归属,下列哪一项说法是正确的?(2018/回忆/单)
在相同条件下的同一种岩石,重度大,说明()。
用友软件中,关于账套主管的说法正确的是()、
甲公司为某企业集团的一个投资中心,X是甲公司下设的一个利润中心,相关资料如下:资料一:2015年X利润中心的营业收入为120万元。变动成本为72万元,该利润中心副主任可控固定成本为10万元,不可控但应由该利润中心负担的固定成本为8万元。资料二:甲公司2
行政机关提供行政许可申请格式文本可以收费。()
下列与水果有关的说法错误的是:
Agroupofpeopleworkingtogetherforabusiness(生意).Thepeoplemaybewillingtohelpyou.
最新回复
(
0
)