OG 43,一个没问过的问题

arrow9999

Passage 112 (12/17)

Homeostasis, an animal’s maintenance of certain internal variables within an acceptable range, particularly in extreme physical environments, has long interested biologists. The desert rat and the camel in the most water-deprived environments, and marine vertebrates in an all-water environment, encounter the same regulatory problem: maintaining adequate internal fluid balance.

For desert rats and camels, the problem is conservation of water in an environment where standing water is nonexistent, temperature is high, and humidity is low. Despite these handicaps, desert rats are able to maintain the osmotic pressure of their blood, as well as their total body-water content, at approximately the same levels as other rats. One countermeasure is behavioral: these rats stay in burrows during the hot part of the day, thus avoiding loss of fluid through panting or sweating, which are regulatory mechanisms for maintaining internal body temperature by evaporative cooling (evaporative cooling: 蒸发冷却). Also, desert rats’ kidneys can excrete a urine having twice as high a salt content as sea water.

Camels, on the other hand, rely more on simple endurance. They cannot store water, and their reliance on an entirely unexceptional kidney results in a rate of water loss through renal function significantly higher than that of desert rats. As a result, camels must tolerate losses in body water of up to thirty percent of their body weight. Nevertheless, camels do rely on a special mechanism to keep water loss within a tolerable range: by seating and panting only when their body temperature exceeds that which would kill a human, they conserve internal water.

Marine vertebrates experience difficulty with their water balance because though there is no shortage of seawater to drink, they must drink a lot of it to maintain their internal fluid balance. But the excess salts from the seawater must be discharged somehow, and the kidneys of most marine vertebrates are unable to excrete a urine in which the salts are more concentrated than in seawater. Most of these animals have special salt-secreting organs outside the kidney that enable them to eliminate excess salt.

262. According to the passage, the camel maintains internal fluid balance in which of the following ways?罗马数字题

I.      By behavioral avoidance of exposure to conditions that lead to fluid loss

II.     By an ability to tolerate high body temperatures

III.    By reliance on stored internal fluid supplies

(A) I only

(B) II only

(C) I and II only

(D) II and III only（B）

(E) I, II, and III

我想问的是I中 Camels, on the other hand, rely more on simple endurance，为什么不能理解为camel也有用RAT的方法，只是更少点呢？ 谢谢！

swlfx

MORE对应的意思正是更少点啊

arrow9999

更少点，就代表有啊？所以I应该是真确的啊？

ProteinMonica

因为文中没有提Camel "By behavioral avoidance of exposure to conditions that lead to fluid loss" 即使rely more on simple endurance，也不能说明，因为有可能是依赖其他手段，但并不一定是rat的方式。切记：文中没有说的一概不知道