→ Mammals and birds generally maintain body temperature within a narrow range (36-38℃ for most mammals and 39-42℃ for most birds) that is usually considerably warmer than the environment. Because heat always flows from a warm object to cooler surroundings, birds and mammals must counteract the constant heat loss. This maintenance of warm body temperature depends on several key adaptations. The most basic mechanism is the high metabolic rate of endothermy itself. Endotherms can produce large amounts of metabolic heat that replace the flow of heat to the environment, and they can vary heat production to match changing rates of heat loss. Heat production is increased by such muscle activity as moving or shivering. In some mammals, certain hormones can cause mitochondria to increase their metabolic activity and produce heat instead of ATP. This nonshivering thermogenesis (NST) takes place throughout the body, but some mammals also have a tissue called brown fat in the neck and between the shoulders that is specialized for rapid heat production. Through shivering and NST, mammals and birds in cold environments can increase their metabolic heat production by as much as 5 to 10 times above the minimal levels that occur in warm conditions.
→ Another major thermoregulatory adaptation that evolved in mammals and birds is insulation (hair, feathers, and fat layers), which reduces the flow of heat and lowers the energy cost of keeping warm. Most land mammals and birds react to cold by raising their fur or feathers, thereby trapping a thicker layer of air.
Humans rely more on a layer of fat just beneath the skin as insulation; goose bumps are a vestige of hair-raising left over from our furry ancestors. 
Vasodilation and vasoconstriction also regulate heat exchange and may contribute to regional temperature differences within the animal. 
For example, heat loss from a human is reduced when arms and legs cool to several degrees below the temperature of the body core, where most vital organs are located. 
→ Another major thermoregulatory adaptation that evolved in mammals and birds is insulation (hair, feathers, and fat layers), which reduces the flow of heat and lowers the energy cost of keeping warm. Most land mammals and birds react to cold by raising their fur or feathers, thereby trapping a thicker layer of air.
Humans rely more on a layer of fat just beneath the skin as insulation; goose bumps are a vestige of hair-raising left over from our furry ancestors. Vasodilation and vasoconstriction also regulate heat exchange and may contribute to regional temperature differences within the animal. For example, heat loss from a human is reduced when arms and legs cool to several degrees below the temperature of the body core, where most vital organs are located.
单选题
According to paragraph 1, the most fundamental adaptation to maintain body temperature is
A. the heat generated by the metabolism
B. a shivering reflex in the muscles
C. migration to a warmer environment
D. higher caloric intake to match heat loss
A. the heat generated by the metabolism
B. a shivering reflex in the muscles
C. migration to a warmer environment
D. higher caloric intake to match heat loss
【正确答案】
A
【答案解析】"The most basic mechanism [for maintenance of warm body temperature] is the high metabolic rate." Choices B, C, and D are all ways to maintain body temperature, but they are not the most fundamental adaptation.
单选题
Based on information in paragraph 1, which of the following best explains the term "thermogenesis"?
A. Heat loss that must be reversed
B. The adaptation of brown fat tissue in the neck
C. The maintenance of healthy environmental conditions
D. Conditions that affect the metabolism
A. Heat loss that must be reversed
B. The adaptation of brown fat tissue in the neck
C. The maintenance of healthy environmental conditions
D. Conditions that affect the metabolism
【正确答案】
D
【答案解析】"In some mammals, certain hormones can cause mitochondria to increase their metabolic activity and produce heat instead of ATP. This nonshivering thermogenesis (NST) " Choice A is not correct because thermogenesis is the activity that generates heat, not the heat loss. Choice B is not correct because brown fat is one example of a more generalized process. Choice Cis not correct because thermogenesis is a response to the environment to maintain the health of the animal, not a process that maintains the environment.
单选题
Which of the sentences below best expresses the information in the highlighted statement in the passage? The other choices change the meaning or leave out important information.
A. An increase in heat production causes muscle activity such as moving or shivering.
B. Muscle activity like moving and shivering will increase heat production.
C. Moving and shivering are muscle activities that increase with heat.
D. When heat increases, the production of muscle activity also increases.
A. An increase in heat production causes muscle activity such as moving or shivering.
B. Muscle activity like moving and shivering will increase heat production.
C. Moving and shivering are muscle activities that increase with heat.
D. When heat increases, the production of muscle activity also increases.
【正确答案】
B
【答案解析】A passive grammatical structure in the passage is paraphrased by an active grammatical structure in the answer choice.
单选题
The word minimal in the passage is closest in meaning to
A. most recent
B. most active
C. newest
D. smallest
A. most recent
B. most active
C. newest
D. smallest
【正确答案】
D
【答案解析】In this passage, smallest is a synonym for "minimal./
单选题
In paragraph 2, the author explains the concept of vasodilation and vasoconstriction by
A. describing the evolution in our ancestors
B. giving an example of heat loss in the extremities
C. comparing the process in humans and animals
D. identifying various types of insulation
A. describing the evolution in our ancestors
B. giving an example of heat loss in the extremities
C. comparing the process in humans and animals
D. identifying various types of insulation
【正确答案】
B
【答案解析】"For example, heat loss from a human is reduced when arms and legs cool." Choice A is not correct because goose bumps, not heat loss in the extremities, is a vestige of our evolution. Choice C is not correct because no direct comparisons of these processes are made in the paragraph. Choice D is not correct because the types of insulation are mentioned before the concept of vasodilatation and vasoconstriction are introduced.
单选题
The word regulate in the passage is closest in meaning to
A. protect
B. create
C. reduce
D. control
A. protect
B. create
C. reduce
D. control
【正确答案】
D
【答案解析】In this passage, controlis a synonym for "regulate." Context comes from the reference to " temperature differences" at the end of the same sentence.
单选题
According to paragraph 3, why do many marine animals require a layer of blubber?
A. Because marine animals have lost their hair during evolution
B. Because heat is lost in water twice as fast as it is in air
C. Because dry hair does not insulate marine animals
D. Because they are so large that they require more insulation
A. Because marine animals have lost their hair during evolution
B. Because heat is lost in water twice as fast as it is in air
C. Because dry hair does not insulate marine animals
D. Because they are so large that they require more insulation
【正确答案】
B
【答案解析】"The loss of heat to water occurs 50 to 100 times more rapidly than heat loss to air." Choice A is not correct because hair loses insulating power when wet, but the evolution of marine animals is not mentioned. Choice C is not correct because dry hair insulates better than wet hair. Choice D is not correct because there are land animals that are of similar size.
单选题
The word those in the passage refers to
A. marine animals
B. core temperatures
C. land mammals
D. metabolic rates
A. marine animals
B. core temperatures
C. land mammals
D. metabolic rates
【正确答案】
D
【答案解析】... marine mammals maintain body core temperatures of about 36-38℃ with metabolic rates about the same as those [metabolic rates] of land mammals of similar size./
单选题
Why does the author mention chickadees in paragraph 4?
A. To discuss an animal that regulates heat very well
B. To demonstrate why chickadees have to eat so much
C. To mention an exception to the rules of thermoregulation
D. To give a reason for heat production in small animals
A. To discuss an animal that regulates heat very well
B. To demonstrate why chickadees have to eat so much
C. To mention an exception to the rules of thermoregulation
D. To give a reason for heat production in small animals
【正确答案】
A
【答案解析】.. capable of astonishing feats of thermoregulation. For example, small birds called chickadees... hold body temperature nearly constant." Choice B is not correct because the food supply supports thermoregulation, which is the main point of the example. Choice C is not correct because chickadees are capable of astonishing feats of thermoregulation. Choice D is not correct because the reason for heat production in animals is explained before the example of the chickadee.
单选题
In paragraph 6, the author states that evaporative cooling is often accomplished by all of the following methods EXCEPT
A. by spreading saliva over the area
B. by urinating on the body
C. by panting or fluttering a pouch
D. by immersing themselves in water
A. by spreading saliva over the area
B. by urinating on the body
C. by panting or fluttering a pouch
D. by immersing themselves in water
【正确答案】
D
【答案解析】Choice A is mentioned in paragraph 6, sentence 7. Choice B is mentioned in paragraph 6, sentence 8. Choice C is mentioned in paragraph 6, sentences 3 and 4.
单选题
The word enhance in the passage is closest in meaning to
A. simplify
B. improve
C. replace
D. interrupt
A. simplify
B. improve
C. replace
D. interrupt
【正确答案】
B
【答案解析】In this passage, improve is a synonym for "enhance." Context comes from the reference to "promote" in the previous sentence.
单选题
Look at the four squares [■] that show where the following sentence could be inserted in the passage.
The insulating power of a layer of fur or feathers mainly depends on how much still air the layer traps.
Where could the sentence best be added?
Click on a square [■] to insert the sentence in the passage.
A. Square Ａ.
B. Square Ｂ.
C. Square Ｃ.
D. Square Ｄ.
The insulating power of a layer of fur or feathers mainly depends on how much still air the layer traps.
Where could the sentence best be added?
Click on a square [■] to insert the sentence in the passage.
A. Square Ａ.
B. Square Ｂ.
C. Square Ｃ.
D. Square Ｄ.
【正确答案】
A
【答案解析】Reference is a transitional device that connects the insert sentence with the previous sentence. "... a layer of fur or feathers" and "how much still air the layer [of fur or feathers] traps" in the insert sentence refers to "... fur or feathers" and "a thicker layer of air" in the previous sentence.
填空题
Directions: An introduction for a short summary of the passage appears below. Complete the summary by selecting the THREE answer choices that mention the most important points in the passage. Some sentences do not belong in the summary because they express ideas that are not included in the passage or are minor points from the passage.
This question is worth 2 points.
Thermoregulation is the process by which animals control body temperatures within healthy limits.
·__________
·__________
·__________
A. Although hair can be a very efficient nsulation when it is dry and it can be raised, hair becomes ineffective when it is submerged in cold water.
B. Some animals with few adaptations for thermoregulation migrate to moderate climates to avoid the extreme weather in the polar regions and the tropics.
C. Mammals and birds use insulation to mit- igate heat loss, including hair and feathers that can be raised to trap air as well as fat or blubber under the skin.
D. Some birds have a special pouch in the mouth, which can be fluttered to increase evaporation and decrease their body temperatures by as much as 20℃.
E. Endotherms generate heat by increasing muscle activity, by releasing hormones into their blood streams, or by producing heat in brown fat tissues.
F. Panting, sweating, and spreading saliva or urine on their bodies are all options for the evaporative cooling of animals in hot environmental conditions.
This question is worth 2 points.
Thermoregulation is the process by which animals control body temperatures within healthy limits.
·__________
·__________
·__________
Answer Choices
A. Although hair can be a very efficient nsulation when it is dry and it can be raised, hair becomes ineffective when it is submerged in cold water.
B. Some animals with few adaptations for thermoregulation migrate to moderate climates to avoid the extreme weather in the polar regions and the tropics.
C. Mammals and birds use insulation to mit- igate heat loss, including hair and feathers that can be raised to trap air as well as fat or blubber under the skin.
D. Some birds have a special pouch in the mouth, which can be fluttered to increase evaporation and decrease their body temperatures by as much as 20℃.
E. Endotherms generate heat by increasing muscle activity, by releasing hormones into their blood streams, or by producing heat in brown fat tissues.
F. Panting, sweating, and spreading saliva or urine on their bodies are all options for the evaporative cooling of animals in hot environmental conditions.