[討論]OG Passage43-biology

[Grace]

Passage 43
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(調整的) problem: maintaining adequate internal fluid balance. (Thesis Statement 整篇文章主題句)
總結: 作者以homeostatis 引導主題, 並分成兩個extreme physical enviroment 舉出三個例子來做說明(後面三段主題),


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 (對策) is behavioral: these rats stay in burrows (hole) during the hot part of the day, thus avoiding loss of fluid through panting (氣喘) or sweating, which are regulatory mechanisms for maintaining internal body temperature by evaporative
cooling. (ETS detail) Also, desert rats’ kidneys can excrete (排出) a urine having twice as high a salt content as sea water.

總結: How do desert rats keep from water loss?

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 thrity percent of their body weight. Nevertheless, camels rely on a special mechanism to keep water loss within a tolerable range: by sweating and panting only when their body temperature exceeds that which would kill a human, they conserve internal water (redundant information, since readers already know that).

總結: How do camels keep from water loss campared with desert rats?

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.

總結: How do marine vertebrates maintain their internal fluid balance?



261. Which of the following most accurately states the purpose of the passage? (主題)
(A) To compare two different approaches to the study of homeostasis
(B) To summarize the findings of several studies regarding organisms’ maintenance of internal
variables in extreme environments
(C) To argue for a particular hypothesis regarding various organisms’ conservation of water in
desert environments
(D) To cite examples of how homeostasis is achieved by various organisms (生物體)
(E) To defend a new theory regarding the maintenance of adeuate fluid balance

262. According to the passage, the camel maintains internal fluid balance in which of the
following ways?
I. By behavioral avoidance of exposure to conditions that lead to fluid loss (rats)
II. By an ability to tolearte high body temperatures (camels)
III. By reliance on stored internal fluid supplies (irrlevant)
(A) I only
(B) II only
(C) I and II only
(D) II and III only
(E) I, II, and III

263. It can be inferred from the passage that some mechanisms that regulate internal body
temperature, like sweating and panting, can lead to which of the following?
(A) A rise in the external body temperature (cooling)
(B) A drop in the body’s internal fluid level
(C) A decrease in the osmotic pressure of the blood (rats)
(D) A decrease in the amount of renal water loss (unmentioned)
(E) A decrease in the urine’s salt content (only rats mentioned )

264. It can be inferred from the passage that the author characterizes the camel’s kidney as
“entirely unexceptional” (line 24) primarily to emphasize that it
(A) functions much as the kidney of a rat functions (not as much)
(B) does not aid the camel in coping with the exceptional water loss resulting from the extreme
conditions of its environment
(C) does not enbale the camel to excrete as much salt as do the kidneys of marine vertebrates
(D) is similar in structure to the kidneys of most mammals living in water-deprived
environments
(E) requires the help of other organs in eliminating excess salt (marine verterbrate)

[agk99]

先頂，兩周內進度趕上一定加入討論

[游客]

by sweating and panting only when their body temperature exceeds that which would kill a human, they conserve internal water
=>
1.They conserve internal water by sweating and panting only when their body temperature exceeds that which would kill a human
2.This sentence only tell us when camel have to sweat and pant
3.so "They conserve internal water" is redundant information and misunderstand reader, since readers already know that.

[游客]

homeostatis:The ability of an organism to maintain a constant internal environment (i.e. body temperature, fluid content, etc.) though regulatory mechanisms that compensate for a changing external environment

[agk99]

本題講駱駝，基本上ok

[agk99]

一、這一篇基本上只要讀三段，第四段根本沒考
如此得到一個結論，若是像這種首段先講結論，後面是舉例說明，則乾脆讀完第一段後就直接做題，特別是機考的第四篇最好採用此法(只是用上的機率不高)

二、本篇算是簡單的生物類型題目，但文章簡單，題目就不簡單
261題的BD
263題的BD
都會讓人混滛

三、264 考的entirely unexception kidney，算是一個口氣極強的文字
一方面強調camel的平凡，一方面也突顯，和第二段舉例的desert rat不同
二三段就呈現出不同感覺

[micht]

261. Which of the following most accurately states the purpose of the passage? (主題)

(B) To summarize the findings of several studies regarding organisms’ maintenance of internal variables in extreme environments

(D) To cite examples of how homeostasis is achieved by various organisms (生物體)

B錯, 因為文中並沒有用"several studies" 不同的研究 來探討分析organisms’ 如何maintain adequate internal variables in extreme environments

D正確, 用兩種例子　illustrate how anmials maintain adequate internal fluid balance under most water-deprived environments

[micht]

263 題　重點要往後看找"mechanism"

Nevertheless, camels rely on a special mechanism to keep water loss within a tolerable range: by sweating and panting only when their body temperature exceeds that which would kill a human, they conserve internal water (redundant information, since readers already know that).


to keep water loss within a torlerable range
[說明 mechanism是為了要防止 internal water loss 超過tolerable range有個極限]

因此可證明 當起動 mechanism時一定表示此時　會有部份internal fluid(water) loss => B) A drop in the body's internal fluid level

[James]

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