Total Pageviews

Thursday, August 22, 2013

Reading Comprehension 1

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 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. 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 sweating 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.

1. Which of the following most accurately states the purpose of the passage?
(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
(E) To defend a new theory regarding the maintenance of adequate fluid balance

2. 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
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 (E) I,II , and Ill

3.It can be inferred from the passage that some mechanisms that regulate internal body temperature t like sweating and panting, can lead to which of the following?
(A) A rise in the external body temperature
(B) A drop in the body's internal fluid level
(C) A decrease i n the osmotic pressure of the blood
(D) A decrease in the amount of renal water loss
(E) A decrease in the urine's salt content

4.It can be inferred from the passage that the author characterizes the camel's kidney as"entirely unexceptional"(1ine 27)primarily to emphasize that it
(A) functions much as the kidney of a rat functions
(B) does not aid the camel in coping with the exceptional water loss resulting from the extreme conditions of its environment
(C) does not enable 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

Solution with explanation -

1. To answer this question,look at the passage as a whole since the purpose is reflected in the entire passage.The first paragraph defines homeostasis and names three animals that must maintain internal fluid balance in difficult circumstances.The topic of the second paragraph is how desert rats maintain fluid balance.The third paragraph discusses how camels maintain fluid balance,while the final paragraph describes maintenance of water balance in marine vertebrates。Thus, the overall purpose is to give three examples of how homeostasis is achieved.
(A)Examples of homeostasis are given,but different approaches to studying it are not discussed.
(B)The passage describes examples but it does not summarize studies.
(C)While the passage does discuss two desert animals,it does not present any argument for a particular hypothesis.
(D)Correct.The passage discusses the examples of desert rats,camels,and marine invertebrates to show how these organisms are able to achieve homeostasis.
(E) The passage describes how three organisms maintain water balance,but it presents no theory about it.

The correct answer is D.

2. Inference To answer this question about factual information stated in the passage,read the third paragraph carefully and compare its content to that of each statement.Line 26 says the camels cannot store water, so Statement III is obviously false.Since camels only pant and sweat when they reach temperatures that would kill a human,they must have an ability to tolerate high body temperatures Therefore.Statement II is true.Finally, there is no evidence that camels avoid exposure to conditions that lead to fluid loss.Lines 30-32show that camels suffer high levels of fluid loss. Therefore Statement I is false.The correct answer must include only Statement II,while excluding Statements I and III.
A Statement I is false.
B Correct.Statement II is the only true statement;fines 34.36 show that camels can tolerate high body temperatures.
C Statement II is true.but Statement I is false.
D Statement II is true.but Statement III is false
E Statement II is true.but Statements I and III are false.

The correct answer is B.

3. Inference An inference is drawn from stated information.To answer this question.1ook at the information about sweating and panting lines 17-19 and 30-32. The passage states that desert rats are avoiding loss of fluid through panting or sweating, which are regulatory mechanisms for maintaining internal body temperature by evaporative cooling. These mechanisms reduce internal body temperatures. Additionally, camels conserve internal water (line 36)when they avoid sweating and panting. Therefore, they must lose internal water when they do sweat and pant. Sweating and panting lead to loss of internal water. (A)The passage does not discuss external body temperature;these mechanisms 10wer internal body temperature,and there is no reason to infer external body temperatures might rise.
(B)Correct.Sweating and panting lead to loss of fluid, and avoiding them helps camels conserve internal water.
(C)The passage states that desert rats are able to maintain the osmotic pressure of their blood, as well as their total body-water content(1ines14-16)and does not connect changes in osmotic pressure to temperature-regulating mechanisms such as sweating and panting. While the passage does discuss renal water does not relate this to temperature-regulating mechanisms like sweating and panting.
(E) The passage does not relate body temperature regulators like sweating and panting to changes in the urine's salt content.

The correct answer is B.

4. Inference To answer this question,1ook at the phrase entirely unexceptional in the context of the passage.Desert rats and camels share the problem of conserving water in an environment where water is lacking, temperature is high, and humidity is low (lines 12—13).Desert rats have as part of their coping mechanisms exceptional kidneys that produce urine with a high salt content.The author compares camels‟ kidneys to those of desert rats and shows that the camels have ordinary kidneys that do not help the camels conserve water.
A Since a contrast is drawn between the kidneys of camels and those of desert rats,the two must function differently.
B Correct.The camel's kidney does nothing special to help the camel cope with its difficult environment. C No comparison between the kidneys of camels and the kidneys of marine vertebrates is made.
D There is no information given about the kidney structure of most mammals in desert environments so this conclusion is not justified.
E Marine vertebrates have other organs that help eliminate extra salt;camels do not.

The correct answer is B.

No comments:

Post a Comment

Comments :