2014年8月16日托福阅读真题P3+题目+答案：Temperature Regulation in Marine Organisms

2014年8月16日托福阅读真题P3+题目+答案：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.

1. The word "sustained" in the passage is closest in meaning to

A.intense

B.necessary

C.continued

D.physical

答案：C

2. According to paragraph 2, the body temperature of strong-swimming fishes is usually above that of their surroundings probably so they can

A.generate heat to warm themselves in cold waters

B.have enough energy for prolonged activity

C.generate metabolic heat for muscular activity

D.retain heat for later use when the surrounding conditions change

答案：B

3. According to paragraph 2, some intertidal animals are not considered true poikilotherms because they

A.can change color and therefore the amount of heat that is absorbed

B.keep their body temperature lower than that of the ambient environment

C.use various techniques to lower their body temperature when overheated by the Sun

D.match their body temperature directly with the air temperature

答案：B

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.

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