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[机经题库答案] 托福阅读生物类真题Temperature Regulation in Marine Organisms原文+题目汇总

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发表于 2017-5-15 14:46 |显示全部楼层
类别:生物类
真题140816CN-P3
Title:Temperature Regulation in Marine Organisms
There are two  extremes of temperature regulation in organisms. Homeotherms are organisms that regulate body temperature  to a constant level, usually above that of the ambient (surrounding) environment. A constant and  relatively high body temperature enables biochemical  reactions to occur in a relatively constant internal environment and at a relatively high  rate. Most birds have a body  temperature of about 40℃, whereas the temperature of most marine mammals is about  38℃.  Because  such temperatures are much higher than that of most seawater, marine homeotherms lose heat rapidly to the  surrounding environment.  
There is another completely different style  of living. Poikilotherms are organisms whose  body temperature conforms to that of the ambient environment. All subtidal marine invertebrates and most fishes  fit into this  category. There is an interesting intermediate status in which body  temperature is usually  somewhat higher than ambient temperature. Strong-swimming fishes, such  as skipjack tuna and yellowfin tuna, have this intermediate  status. Their rise in temperature above ambient conditions stems from  metabolic heat generated by muscular activity (swimming) combined with a heat  retention mechanism. The temperature rise is  probably necessary to generate the increased biochemical reaction rates that are  needed for sustained activity. In contrast, some intertidal animals are not true Poikilotherms,  they maintain themselves at lower-than-ambient body temperature, using both evaporation and circulation of body fluids to avoid  being heated at low tide by the Sun. Their  body temperatures, therefore, differ from that  of an inanimate object of the same size and  shape that might be placed on the shore. Intertidal organisms absorb and lose heat  directly to the air. Darker-colored forms  can absorb more heat than can light-colored forms, therefore, variation in color can reflect  differences in adaptation to the capture  of solar energy  at different latitudes.
Ocean temperatures are usually less than 27℃ and may be less than  0℃ in some locations and during some  seasons. Therefore, most  homeothermic mammals and birds must lose heat continuously  to the environment. Their skin is the main pathway  of heat loss,  especially by direct  conduct of heat  from the skin  to the contacting colder water. Because animals have a circulatory system,  heat loss from the  body surface also  occurs as warm  interior blood is transferred and  moves into contact with the periphery of the body.  Their bodies also  radiate heat, usually in the infrared part of the  spectrum. Finally, as animals exhale, the resulting evaporation of water involves a  considerable loss of heat.
The first line of defense  against heat loss is a well-insulated body surface. Marine birds deal with this problem by means of specially adapted  feathers. A series  of interlocking contour  feathers encloses a thick layer  of down feathers that traps stationary air, which  in turn acts as an insulating layer.  Whales, porpoises, and seals  are insulated against the lower sea  temperatures by a thick layer  of subcutaneous fat. Sea  otters lack such a layer, but they constantly preen and fluff up a relatively thick layer of fur. Such  mechanisms are only partly successful, however, and to generate  more body heat to maintain a constant temperature, marine mammals usually must have a higher  metabolic rate than similarly sized terrestrial (land) animals.
In marine mammals that have limbs,  the limbs are the principal sources of heat loss because  they expose a relatively greater  amount of body surface area per unit volume  to cold water.  However, warm arterial blood must be supplied to limbs, such  as the flipper  of a porpoise. Heat loss  in porpoises is minimized by a  countercurrent heat exchanger. The arteries are  surrounded by veins,  within which blood  is returning to the core  of the animal. At any contact  point, the artery,  which is on the inside, is warmer than a surrounding vein, so heat  is lost to the returning venous blood flow. Heat is thus  reabsorbed and returned to the porpoise’s body core. This spatial  relationship of circulatory vessels minimizes heat loss to the flipper and thence to the water.  Although the anatomical details are quite different, fishes such as skipjack  tuna have a circulatory anatomy based on the same overall design. Arteries and  veins in the near-surface musculature are in contact, and in arteries and veins,  respectively, blood flows in opposite directions.

Paragraph 2  
There is another completely different style  of living. Poikilotherms are organisms whose  body temperature conforms to that of the ambient environment. All subtidal marine invertebrates and most fishes  fit into this  category. There is an interesting intermediate status in which body  temperature is usually  somewhat higher than ambient temperature. Strong-swimming fishes, such  as skipjack tuna and yellowfin tuna, have this intermediate  status. Their rise in temperature above ambient conditions stems from metabolic heat generated by muscular activity (swimming) combined with a heat  retention mechanism. The temperature rise is  probably necessary to generate the increased biochemical reaction rates that are  needed for sustained activity. In  contrast, some intertidal animals are not  true Poikilotherms, they  maintain themselves at lower-than-ambient body temperature, using both evaporation and circulation of body fluids to avoid  being heated at low tide by the Sun. Their  body temperatures, therefore, differ from that  of an inanimate object of the same size and  shape that might be placed on the shore. Intertidal organisms absorb and lose heat  directly to the air. Darker-colored forms  can absorb more heat than can light-colored forms, therefore, variation in color can reflect  differences in adaptation to the capture  of solar energy  at different latitudes.  
  
1.    The word "sustained" in the passage is closest  in meaning to  
¡  intense  
¡  necessary  
¡  continued  
¡  physical  
  
2.    According to paragraph  2, the body temperature of strong-swimming fishes is usually above that of their surroundings probably so they can  
¡  generate heat to warm  themselves in cold waters  
¡  have enough energy for  prolonged activity  
¡  generate metabolic  heat for muscular activity  
¡  retain heat for later  use when the surrounding conditions change  
  
3.    According to paragraph 2, some intertidal animals are not considered true poikilotherms  because they  
¡  can change color and  therefore the amount of heat that is absorbed  
¡  keep their body  temperature lower than that of the ambient  environment  
¡   use various techniques to lower their body  temperature when overheated by the  Sun  
¡  match their body  temperature directly with the air temperature  
  
Paragraph 3  
Ocean temperatures are usually less than 27℃ and may be less than 0℃ in some locations and during some  seasons. Therefore, most  homeothermic mammals and birds must lose heat continuously  to the environment. Their skin is the main pathway  of heat loss,  especially by direct  conduct of heat  from the skin  to the contacting colder water. Because animals have a circulatory system,  heat loss from the  body surface also  occurs as warm  interior blood is transferred and  moves into contact with the periphery of the body.  Their bodies also  radiate heat, usually in the infrared part of the spectrum.  Finally, as animals exhale, the resulting evaporation of water involves a considerable loss of heat.  
  
4.    The word "considerable" in the passage is  closest in meaning to  
¡  gradual  
¡  unusual  
¡  temporary  
¡  significant
   
5.    According to paragraph  3, all of the following contribute to heat loss in homeothermic  animals EXCEPT  
¡  heat transfer from the  skin to the water  
¡  the  movement of blood to the animal’s periphery  
¡  an increase in their  activity during certain seasons  
¡  the evaporation of  water during breathing
    
The first line of defense  against heat loss is a well-insulated body surface. Marine birds deal with this problem by means of specially adapted  feathers. A series  of interlocking contour  feathers encloses a thick layer  of down feathers that traps stationary air, which in turn  acts as an insulating layer.  Whales, porpoises, and seals  are insulated against the lower sea  temperatures by a thick layer  of subcutaneous fat. Sea  otters lack such a layer, but they constantly preen and fluff up a relatively thick layer of fur. Such  mechanisms are only partly successful, however, and to generate  more body heat to maintain a constant temperature, marine mammals usually must have a higher  metabolic rate than similarly sized terrestrial (land) animals.  
  
6.    The word "stationary" in the passage is closest  in meaning to  
¡  warm  
¡  surface  
¡  nonmoving  
¡  nearby  
  
7.    All of the following are mentioned in paragraph 4 as defenses against heat loss  
EXCEPT  
¡  subcutaneous fat  
¡  layers of feathers  
¡  a thick layer of fur  
¡  constant metabolic rates  
  
8.    What can be inferred  from the comparison of terrestrial animals to marine animals in the  last sentence of paragraph 4?  
¡  An  animal’s size is not the only factor affecting its metabolic rate.  
¡   An animal’s size determines  what mechanism can be successfully used to prevent heat loss.  
¡  Smaller animals are  more successful than larger ones at preventing heat loss.  
¡   Terrestrial  animals have a wider variety of mechanisms for  preventing heat loss than marine animals do.  
  
9.    Paragraph 4 expands on  paragraph 3 by  
¡   presenting various reasons  why first-time defenses are inadequate to deal  with the problem described in paragraph 3  
¡   discussing mechanisms that marine animals use  to reduce the problem described in  paragraph 3  
¡   identifying  specific ways that  the problem described in paragraph 3 harms  marine animals  
¡   explaining  why the problem  described in paragraph 3 harms some marine animals more than others
  
In marine mammals that have limbs,  the limbs are the principal sources of heat loss because  they expose a relatively greater  amount of body surface area per unit volume  to cold water.  However, warm arterial blood must be supplied to limbs, such  as the flipper  of a porpoise. Heat loss  in porpoises is minimized by a  counter current heat exchanger. The arteries are  surrounded by veins,  within which blood  is returning to the core  of the animal. At any contact  point, the artery, which is on the inside, is warmer than a surrounding vein, so heat  is lost to the returning venous blood flow. Heat is thus  reabsorbed and returned to the porpoise’s body core. This spatial  relationship of circulatory vessels minimizes heat loss to the flipper and thence to the water.  Although the anatomical details are quite different, fishes such as skipjack tuna have a circulatory anatomy based on the  same overall design. Arteries and  veins in the near-surface musculature are in contact, and in arteries and veins,  respectively, blood flows in opposite directions.  
  
10.  The word "overall" in the passage is closest in  meaning to  
¡  simple  
¡  effective  
¡  well-planned  
¡  general  
  
11.  According to paragraph  5, some marine mammals that have limbs minimize heat loss by using a system in which  
¡   vessels that return blood to  the animal’s core absorb heat from warm interior  arteries  
¡  blood returning to the  core is warmer than blood flowing from the  core  
¡  the placement of the  arteries reduces blood flow to the veins  
¡  both arteries and  veins are in contact with near-surface musculature  
  
12.  Why  does the author discuss ¯fishes such as  skipjack tuna‖?  
¡  To explain by contrast  why the circulatory anatomy of porpoises is  efficient  
¡   To show that marine animals other than mammals  use a countercurrent exchange system to minimize heat loss  
¡  To identify and illustrate a type of circulatory anatomy that is common  in fishes  
¡   To provide evidence that the amount of heat  marine animals lose increases with increased body surface area  
  
Paragraph 2  
There is another completely different style of living. ■ Poikilotherms  are organisms whose body temperature conforms to that  of the ambient environment. ■All subtidal marine invertebrates and most fishes  fit into this category.  ■There is an interesting  intermediate status in which body  temperature is usually  somewhat higher than ambient temperature. ■ Strong-swimming fishes, such as skipjack tuna and yellow fin tuna, have this intermediate status.  Their rise in temperature above ambient conditions stems from metabolic heat generated by muscular activity (swimming) combined with a heat  retention mechanism. The  temperature rise is probably  necessary to generate the increased biochemical reaction rates that are needed for sustained  activity. In contrast, some intertidal animals are not true  Poikilotherms, they maintain themselves at lower-than-ambient body temperature, using  both evaporation and circulation of body fluids  to avoid being heated  at low tide by the Sun. Their body temperatures, therefore, differ from that of  an inanimate object of the same size and shape that might be placed on the shore. Intertidal organisms absorb and  lose heat directly to the air. Darker-colored forms can absorb more heat than can  light-colored forms, therefore, variation in color  can reflect differences in adaptation to the capture  of solar energy at different latitudes.  
  
13.  Look at  the four squares [■] that indicate where the  following sentence can be added to  the passage.  
However, not all marine  organisms can be easily classified as either homeotherms or poikilotherms.
Where would the sentence best fit?  
  
14.  Directions: An introductory sentence for a brief  summary of the passage is provided  below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong  in the summary  because they express  ideas that are not presented in the passage or are minor  ideas in the  passage. This question is worth 2 points.  
Drag your choices to the  spaces where they belong. To review the passage, click on View Text.  
   
Marine and other organisms are classified as      homeotherms      if they maintain a constant body temperature      and as      poikilotherms if their body temperature      matches that of the environment.      
   
  

Answer Choices
¡   Although strong-swimming  fishes and intertidal organisms  have body temperatures that are higher or lower than ambient  temperatures, most fishes and  subtidal marine organisms are poikilotherms.
¡   There are no homeotherms in cold ocean waters because it is too difficult for homeotherms to prevent  heat loss in these environments.  
¡   Features such as fur help  reduce heat loss, but marine homeotherms require a higher metabolism than do terrestrial homeotherms of similar size to maintain  a constant body temperature.
¡   Some organisms are thought  to have various methods of heat regulation in order to  maintain different body temperatures at different times of year.  
¡   Marine homeotherms lose  heat to the environment through respiration  and other means, the most important  being skin contact with colder seawater.  
¡   Animals with limbs are at a disadvantage regarding body temperature because their circulatory anatomy is poorly designed for managing heat loss.  
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