首页
登录
职称英语
The two claws of the mature American lobster are decidedly different from ea
The two claws of the mature American lobster are decidedly different from ea
游客
2025-03-29
4
管理
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. [br] 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://tihaiku.com/zcyy/4017284.html
相关试题推荐
OurculturehascausedmostAmericanstoassumenotonlythatourlanguagei
OurculturehascausedmostAmericanstoassumenotonlythatourlanguagei
OurculturehascausedmostAmericanstoassumenotonlythatourlanguagei
Ihaveheardmanydifferent______ofthesamestory.A、sayingsB、statementsC、co
Thetactthattheyreactedsodifferentlywasareflectionoftheirdifferent__
Therearedifferent______ofbooksinalibrary.(2007年中国矿业大学考博试题)A、speciesB、bio
PresidentJimmyCarterinturnagreedtotrytoreduceAmericanoilimportsand
TheAmericanRevolutionhadnomedievallegalinstitutionsto___ortorootout,
It’ssocoldoutsidethatmyfingersfeel______.A、deadB、indifferentC、unawareD
Iceandwaterarethesame______indifferentforms.A、materialB、stuffC、elemen
随机试题
Ourfamilydoctor’sclinic________atthejunctionoftwobusyroads.A、restsB、st
Somepeoplethinkthatuniversitiesshouldprovidestudentswiththeknowledgea
Directions:Forthispart,youareallowed30minutestowriteashortessayent
从存储大量数据、图表的检索系统中获取数值型信息的检索类型是( )。A.数据检索
用数量指标对每种情况中可能有或可能没有的心理现象进行分析的方法是()A.趋势分
基金管理人合规培训的具体内容包括()。 Ⅰ.国家制定颁布的与基金行业有关的法
51、当交换机用于传输SV或GOOSE等可靠性要求较高的信息时应采用光接口。
某空置的无电梯旧写字楼的建筑面积为2000m2,剩余经济寿命为35年,在价值时点
下列各项中,属于借款人的权利的有()。A.自主向主办银行或者其他银行的经办机构
烧伤最常见的死亡原因是 A.休克 B.ARDS C.肾功能衰竭 D.感
最新回复
(
0
)