首页
登录
职称英语
Comparatively few fresh-water species of fishes are limited in their distrib
Comparatively few fresh-water species of fishes are limited in their distrib
游客
2024-02-05
47
管理
问题
Comparatively few fresh-water species of fishes are limited in their distribution to a single river system, yet not many are found on both sides of a high mountain ridge, such as the Rocky Mountains in North America. That is to say, the fishes of the Mississippi Valley are generally different from those of the Pacific slope.
While it is a well-known fact that the fish life in no two river systems, even though they empty into the sea on the same side of a divide(分水岭), is exactly identical, such streams do have many species in common. The principal rivers of the Atlantic slope of the United States, for example, contain several species common to all of them, including the bullhead catfish, the bluegill sunfish, and the largemouth bass. None of these species can endure salt water, so they cannot move from one river system to another. On the other hand, the more northern streams contain species not found in the southern ones, and vice versa. The common pike, for example, is found in the Atlantic streams from Maryland northward, and the brook trout and yellow perch occur only in the streams from North Carolina southward.
How the present distribution came about must remain a matter of guess. It is quite probable that some of the streams, including those on opposite sides of a divide, may have been connected at one time. Again, streams may be entirely separate during normal weather, but an exceptionally heavy rainfall or the sudden melting of snow in the uplands sometimes causes floods which may form a temporary connection between them, providing a passageway for fishes. It is also possible that water birds may accidentally carry fish or spawn(卵)from one stream to another, or that man may be instrumental in such a transfer.
Evidently, then, fresh-water fishes may become distributed far beyond the confines of the stream of their origin. Then chief factor in limiting the still wider distribution of species is temperature. This forms such an efficient barrier that comparatively few species of fresh-water fishes of the United States extend their range into Mexico. In Panama only one fish common to the fresh waters of the United States has been found, and that is the eel, which is not strictly a fresh-water form, as it enters salt water to spawn and is taken in fairly salty water at other times. [br] According to the passage,______.
选项
A、The Mississippi River and the Pacific slope are on the same side of the Rocky Mountains
B、The Mississippi River and the Pacific slope are on the two sides of the Rocky Mountains
C、The Mississippi River and the Rocky Mountains are on the two sides of the Pacific slope
D、The Pacific slope and the Rocky Mountains are on the two sides of the Mississippi
答案
B
解析
细节题。此题问的是Rocky Mountains,Mississippi Valley和Pacific Slope三者的位置关系。第一段提到极少的淡水鱼会出现在一座高山两边,比如说Rocky Mountains。这也就是说Rocky Mountains东边Mississippi Valley里的鱼与Pacific Slope里的鱼是不同的。这也就说明Rocky Mountains将Pacific Slope和Mississippi Valley隔开了。
转载请注明原文地址:http://tihaiku.com/zcyy/3423280.html
相关试题推荐
Aleadingbiologisthascomparedthephysiology(生理学)offlightedspecieswith
Aleadingbiologisthascomparedthephysiology(生理学)offlightedspecieswith
Aleadingbiologisthascomparedthephysiology(生理学)offlightedspecieswith
Aleadingbiologisthascomparedthephysiology(生理学)offlightedspecieswith
Aleadingbiologisthascomparedthephysiology(生理学)offlightedspecieswith
TheEarthhasbeenstrippedofupto90%ofitsspeciesfivetimesbeforein
TheEarthhasbeenstrippedofupto90%ofitsspeciesfivetimesbeforein
TheEarthhasbeenstrippedofupto90%ofitsspeciesfivetimesbeforein
TheEarthhasbeenstrippedofupto90%ofitsspeciesfivetimesbeforein
TheEarthhasbeenstrippedofupto90%ofitsspeciesfivetimesbeforein
随机试题
What’sthewoman’sproblem?[br][originaltext]M:Hey,Mrs.Jackson.Wouldyo
It’sclearthatsocialmedialikeTwitterandFacebookarechangingtheway
PASSAGEFOUR[br]Whatisthemainideaofthepassage?Secondaryschoolsshouldn
[originaltext]We’velongbeentoldthatanappleadaykeepsthedoctorawa
关于影响计算机X线摄影影像质量的因素说法错误的是A.读出装置激光点直径越小,图像
下列关于沪港股票市场交易互联互通机制试点有关税收政策的理解,不正确的有()。A
《临证指南医案》所说"宜升则健"的脏是()A.肺 B.脾 C.肝 D
1995-20.我国最早的脉学专书《脉经》提出多少种脉象 A.28种B
近来网上出现了一则有关“公务员绿色出行”的报道,即A市教育局通过添置公务自行车
下列哪种不是肝在脂类代谢中的特有作用A.酮体的生成 B.LDL的生成 C.V
最新回复
(
0
)