1、托福-42 及答案解析(总分：136.00，做题时间：90 分钟)一、BREADING/B(总题数：0，分数：0.00)二、BPart 1/B(总题数：1，分数：6.50)ECTOTHERMY AND ENDOTHERMY1 Many biological systems are based on the process of homeostasis, which means “steady state.“ Homeostasis is the ability to maintain balance. Homeostatic mechanisms enable animals to survi
2、ve changes in their external environment by regulating conditions within their bodies. Conditions in the external environment, such as temperature, may vary widely, but conditions in the Uinternal environment/U can vary only within a narrow range necessary for survival.2 Temperature is a Uconstraint
3、/U for animals, all of which must maintain biochemical stability. When an animals body temperature drops too low, its metabolism slows, thus reducing the amount of energy the animal can use for activity. If body temperature rises too high, metabolic reactions become unbalanced, and enzyme activity i
4、s hindered. Animals can succeed only in a limited range of body temperatures, and for most, this is between 0 and 40 degrees Celsius.3 One way to classify animals is to emphasize their source of body heat. For instance, “cold-blooded“ animals are those that must warm their body with heat from the su
5、rrounding environment, and “warm-blooded“ animals are those that can heat themselves. However, these traditional terms are inaccurate and misleading. Some “cold-blooded“ animals, such as lizards, have higher body temperatures when active than many “warm-blooded“ animals have when hibernating. Physio
6、logists prefer the terms “ectotherm“ and “endotherm“ because they reflect the fact that an animals body temperature is a balance between heat loss and heat gain.4 All animals produce heat from cellular metabolism, but in most the heat is conducted away as fast as it is produced, so the amount of hea
7、t obtained from metabolism is very small. In these animals, the ectotherms, body temperature is determined almost entirely by their surroundings. Most invertebrates, fishes, amphibians, and reptiles are ectotherms. In contrast, some animals are able to generate and retain enough heat from metabolism
8、 to elevate their own body temperature to theU optimum/U level. These animals are called the endotherms because the source of their body heat is internal. Mammals, birds, some fishes, and numerous insects are endotherms.5 Ectotherms warm their body mainly by absorbing heat from their environment. Ec
9、totherms cannot control their body temperature physiologically, yet many are able to regulate it behaviorally by selecting areas of the environment with a more favorable temperature. Some, such as desert lizards, Uexploit/U hour-to-hour changes in solar radiation to keep their body temperature relat
10、ively constant. In the morning, the lizard absorbs the suns heat through its head, while keeping the rest of its body protected from the cool air. Later, the lizard will emerge to bask in the sun. At noon, with its body temperature high, it seeks shade under a rock. When the air temperature drops in
11、 the late afternoon, it emerges and lies parallel to the suns rays.6 Endotherms, on the other hand, derive most or all of their body heat from their own metabolism. A consistently warm body temperature requires active metabolism, which includes oxidation of foods, cellular respiration, and muscular
12、contraction. Conversely, a warm body temperature contributes to the high levels of metabolism required for extended periods of intense physical activity. This is one reason endotherms can generally endure vigorous activity longer than ectotherms. However, being endothermic is Uenergetically/U expens
13、ive, especially in a cold environment. Because much of an endotherms daily intake of calories is used to generate heat, the endotherm must eat more food than an ectotherm of the same size.Endothermy allows birds and mammals to stabilize their internal temperature so that biochemical processes and ne
14、rvous system functions can proceed at steady levels of activity. These animals maintain a constant body temperature through a delicate balance between heat production and heat loss. UThis is why endotherms can remain active in winter and exploit habitats denied to ectotherms./U If the animal becomes
15、 too cool, it can generate heat by increasing muscular activity (exercise or shivering), or it can decrease heat loss by increasing insulation. In general, birds and mammals are warmer than their surroundings, but they also have mechanisms for cooling the body in a hot environment. If the animal bec
16、omes too warm, it decreases heat production and increases heat loss by evaporative cooling (sweating or panting).（分数：6.50）(1).In using the term Uinternal environment/U in paragraph 1, the author is talking about A. the animals den B. the animals body C. the animals genetic code D. the animals social
17、 position（分数：0.50）A.B.C.D.(2).The word Uconstraint/U in paragraph 2 is closest in meaning to A. restriction B. reward C. ertainty D. comfort（分数：0.50）A.B.C.D.(3).Why can animals survive only in a limited range of body temperatures? A. Body temperature is a key contributor to metabolic stability. B. A
18、nimals cannot maintain necessary bod,. fluids at extreme temperatures. C. Body temperature is linked to an animal ability to reproduce. D. Most environmental temperatures fall between 0 and 40 degrees Celsius.（分数：0.50）A.B.C.D.(4).According to paragraph 3, why are the terms “cold-blooded“ and “warm-b
19、looded“ inaccurate for classifying animals? A. They imply that warm blood is better. B. They incorrectly identify blood as important in body temperature. C. They suggest that some animals do not like heat. D. They imply that the animals blood is always cold or warm.（分数：0.50）A.B.C.D.(5).The word opti
20、mum in paragraph 4 is closest in meaning to A. environmental B. opposite C. most common D. most favorable（分数：0.50）A.B.C.D.(6).The word exploit in paragraph 5 is closest in meaning to A. get away with B. get used to C. take advantage of D. take care of（分数：0.50）A.B.C.D.(7).Which of the following state
21、ments can be inferred about ectotherms? A. They can engage in physical activity for long periods of time. B. They are the most intelligent animals that live in the desert. C. They must eat all day long to maintain their body temperature. D. They are likely to live where heat from the sun is availabl
22、e.（分数：0.50）A.B.C.D.(8).Why does the author use the term energetically expensive in paragraph 6? A. To point out that intense physical exercise is difficult for animals B. To stress that generating internal body heat requires a lot of calories C. To explain why there are many more ectotherms than end
23、otherms D. To show that endotherms consume too many environmental resources（分数：0.50）A.B.C.D.(9).Which sentence below best expresses the essential information in the highlighted sentence in paragraph 7? Incorrect choices change the meaning in important ways or leave out essential information. A. Beca
24、use endotherms can maintain their body temperature, they can live in cold habitats. B. In winter, endotherms do not allow ectotherms access to the resources they need for survival. C. Endotherms are naturally warmer than ectotherms, so the two kinds of animals prefer different habitats. D. Ectotherm
25、s thrive in cold habitats, but they must compete with endotherms for survival.（分数：0.50）A.B.C.D.(10).All of the following are mentioned as advantages of endothermy EXCEPT A. endurance of intense physical activity B. survival in cold surroundings C. high level of intelligence D. ability to cool the bo
26、dy（分数：0.50）A.B.C.D.(11).Which of the following is a mechanism that promotes heat loss? A. Shivering B. Insulation C. Exercise D. Panting（分数：0.50）A.B.C.D.(12).Look at the four squares, , , , and , which indicate where the following sentence could be added to the passage. Where would the sentence best
27、 fit?Many endotherms maintain a consistent internal temperature even as the temperature of their surroundings fluctuates,All animals produce heat from cellular metabolism, but in most the heat is conducted away as fast as it is produced, so the amount of heat obtained from metabolism is very small.
28、In these animals, the ectotherms, body temperature is determined almost entirely by their surroundings. Most invertebrates, fishes, amphibians, and reptiles are ectotherms. In contrast, some animals are able to generate and retain enough heat from metabolism to elevate their own body temperature to
29、the optimum level. These animals are called the endotherms because the source of their body heat is internal. （分数：0.50）填空项 1:_(13).Select the appropriate phrases from the answer choices and match them to the class of animal that they describe. TWO of the answer choices will NOT be used. This questio
30、n is worth 3 points. Answer Choices A. Are cold-blooded when active and warm-blooded when inactive B. Generate heat internally to achieve the correct body temperature C. Use the environment as their primary source of body heat D. Survive by hibernating when their body becomes too warm E. Need a larg
31、e amount of food to regulate metabolism and body temperature F. Maintain body temperature behaviorally, by seeking sun or shade G. Have bodily mechanisms for controlling heat production and heat loss （分数：0.50）A.B.C.D.E.F.G.三、BPart 2/B(总题数：2，分数：13.50)CANADIAN ENGLISH1 Canadian English is a regional v
32、ariety of North American English that spans almost the entire continent. Canadian English became a separate variety of North American English after the American Revolution, when thousands of Loyalists, people who had supported the British, left the United States and fled north to Canada. Many Loyali
33、sts settled in southern Ontario in the 1780s, and their speech became the basis for what is called General Canadian, a definition based on the Unorms/U of urban middle-class speech.2 Modern Canadian English is usually defined by the ways in which it resembles and differs from American or British Eng
34、lish. Canadian English has Ua great deal in common with/U the English spoken in the United States, yet many Americans identify a Canadian accent as British. Many American visitors to Canada think the Canadian vocabulary sounds British-for example, they notice the British “tap“ and “braces“ instead o
35、f the American “faucet“ and “suspenders.“ On the other hand, many British people identify a Canadian accent as American, and British visitors think the Canadians have become Americanized, saying “gas“ and “truck“ for “petrol“ and “lorry.“3 People who live outside North America often find it difficul
36、t to hear the differences between Canadian and American English. There are many similarities between the two varieties, yet they are far from identical. Canadian English is instantly recognizable to other Canadians, and one Canadian in a crowded room will easily Uspot/U the other Canadian among the
37、North Americans.4 There is no distinctive Canadian grammar. The differences are mainly in pronunciation, vocabulary, and idioms. UCanadian pronunciation reflects the experience of a people struggling for national identity against two strong influences/U. About 75 percent of Canadians use the British
38、 “zed“ rather than the American “zee“ for the name of the last letter of the alphabet. On the other hand, 75 percent of Canadians use the American pronunciation of “schedule,“ “tomato,“ and “missile.“ The most obvious and distinctive feature of Canadian speech is probably its vowel sound, the diphth
39、ong “ou.“ In Canada, “out“ is pronounced like “oat“ in nearby U.S. accents. There are other identifying features of Canadian vowels; for example, “cot“ is pronounced the same as “caught“ and “collar“ the same as “caller.“5 An important characteristic of the vocabulary of Canadian English is the use
40、of many words and phrases originating in Canada itself, such as “kerosene“ and “chesterfield“ (“sofa“). Several words are borrowed from North American Indian languages, for example, “kayak,“ “caribou,“ “parka,“ and “skookum“ (“strong“). The name of the country itself has an Indian origin; the Iroquo
41、is word “kanata“ originally meant “village.“ A number of terms for ice hockey-“face-off, blue-line,“ and “puck“-have become part of World Standard English.6 Some features of Canadian English seem to be unique and are often deliberately identified with Canadian speakers in such contexts as dramatic a
42、nd literary characterizations. Among the original Canadian idioms, perhaps the most famous is the almost universal use of“eh?“ as a tag question, as in “Thats a good movie, eh? Eh“ is also used as a filler during a narrative, as in “Im walking home from work, eh, and Im thinking about dinner. I fina
43、lly get home, eh, and the refrigerator is empty.“7 The traditional view holds that there are no dialects in Canadian English and that Canadians cannot tell where other Canadians are from just by listening to them. The linguists of today disagree with this view. While there is a greater degree of Uho
44、mogeneity/U in Canadian English compared with American English, several dialect areas do exist across Canada. Linguists have identified distinct dialects for the Maritime Provinces, Newfoundland, the Ottawa Valley, southern Ontario, the Prairie Provinces, the Arctic North, and the West.（分数：6.50）(1).
45、According to the passage, how did Canadian English become a distinct variety of North American English? A. Linguists noticed that Canadians spoke a unique dialect. B. A large group of Loyalists settled in one region at the same time. C. Growth of the middle class led to a standard school curriculum.
46、 D. Canadians declared their language to be different from U.S. English.（分数：0.50）A.B.C.D.(2).The word Unorms/U in paragraph 1 is closest in meaning to A. patterns B. history C. words D. ideas（分数：0.50）A.B.C.D.(3).The phrase Ua great deal in common with/U in paragraph 2 is closest in meaning to A. dif
47、ferent words for B. the same problems as C. many similarities to D. easier pronunciation than（分数：0.50）A.B.C.D.(4).In paragraph 2, what point does the author make about Canadian English? A. Canadian English is more similar to American than to British English. B. American and British visitors define C
48、anadian English by their own norms. C. Canadian English has many words that are not in other varieties of English. D. Canadians speak English with an accent that Americans cannot understand.（分数：0.50）A.B.C.D.(5).The word Uspot/U in paragraph 3 is closest in meaning to A. describe B. ignore C. prefer D. find（分数：0.50）A.B.C.D.(6).Which sentence below best expresses the essential information in the highlighted sentence in paragraph 4? Incorrect choices change the meaning in important ways or leave out essential information. A. Canadian English has been strongly influenced by both Bri
