The Origin of Flight in Birds
题目：
Debate over avian origins was stimulated in 1861 when the 150-million-year-old fossil of a bird-like creature was unearthed. Called Archaeopteryx , it has feathers that are almost indistinguishable in form from modern flight feathers, yet it also has many reptilian features, including teeth. Archaeopteryx seems to have been capable of some sort of aerial activity. However, there is some debate over whether it was capable of powering itself through the air by flapping its wings.
Questions regarding the ancestry of modern birds are closely linked to questions about how birds developed the ability to fly. Birds are not the only animals to have evolved this ability, but they are the only ones to use feathers for the airfoil needed to create lift. Thus the evolution of flight in birds depended on feathers. But since feathers serve other functions (such as display and insulation), it is not necessarily true that the evolution of feathers depended on flight. Feathers also could have developed initially to provide insulation to help maintain high body temperature. Warm bodies are required to sustain the kind of activity needed for flapping flight because the chemical reactions required to support rapid repetitive muscle contractions proceed most efficiently at higher temperatures. Thus feathers and the ability to maintain warm body temperatures metabolically (endothermy) were prerequisites for flapping flight in birds. But did birds start flying by flapping? There are two major lines of thought about how, and when, birds evolved the feathers and high internal body temperatures that allowed them to engage in flapping flight.
The Trees-down Theory: For much of the twentieth century the conventional theory held that early birds were arboreal (tree dwelling) and that flight developed from gliding activities similar to those of flying squirrels, which take advantage of air currents as they leap from tree to tree by stretching out but not flapping their arms. According to this arboreal theory, feathers developed from early reptilian scales. The earliest protofeathers in this scenario were envisioned as arising from a genetic mutation that elongated or enlarged scales. Individuals with longer scales benefited because these scales would have increased the surface area of the outstretched forearms. which would have slowed the rate of fall and thus increased the distance of horizontal travel-when leaping from tree to tree. These advantages in turn, it is proposed, would have had survival benefits by reducing the risk of death from falling or from accidentally landing on the ground, where predators waited Further scale elaboration would have increased these advantages and longer, more aerodynamically shaped scales would have been selected for. Over the generations, as scales became more feather-like, short glides gave way to long ones, and gliding flight became possible. Simple gliders could have evolved into intermediate forms like Archaeopteryx, which may have supplemented gliding with weak flapping, and thence to modern birds with flapping flight Endothermy need not have arisen until the ancestors of birds were well differentiated from other reptiles and feathers were sufficiently elaborate to provide some insulating advantage. This theory was generated largely from the observation that Archaeopteryx had feet that could have grasped a branch. These grasping feet are taken as evidence that Archaeopteryx lived in trees. which makes the trees-down theory plausible.
The Ground-up Theory: In contrast, the ground-up, or terrestrial, theory posits that early birds were ground-dwelling, bipedal predators that chased down prey on foot and captured the victims with clawed forelimbs. This sort of behavior, like flapping flight, is best (though not exclusively) supported by a high body temperature. Warm-bodied predators can sustain the rapid repetitive muscle contractions used for running after prey for longer stretches of time than cold-bodied predators. Feathers may have developed for insulation, which would have improved the retention of body heat. Later. feathers might also have improved prey capture or balance while running by increasing the surface area of the extended forelimbs. As feathers enlarged. an airfoil developed, flight became possible and the advantages of flight drove further elaboration of feather structure. The ground-up idea arose from John Ostrom’s proposal linking Archaeopteryx to theropod dinosaurs which were apparently all active. terrestrial. bipedal predators and which increasingly are thought of as likely to have been able to maintain high body temperatures.
1
Debate over avian origins was stimulated in 1861 when the 150-million-year-old fossil of a bird-like creature was unearthed. Called Archaeopteryx , it has feathers that are almost indistinguishable in form from modern flight feathers, yet it also has many reptilian features, including teeth. Archaeopteryx seems to have been capable of some sort of aerial activity. However, there is some debate over whether it was capable of powering itself through the air by flapping its wings.
According to paragraph 1, disagreement exists on which of the following issues concerning Archaeopteryx?
Factual Information Questions事实信息题
AWhether it flew by flapping its wings
BWhether it was able to engage in any kind of aerial activity
CWhy it continued to have so many reptilian features
DWhether its feathers were like modern flight feathers
2
Questions regarding the ancestry of modern birds are closely linked to questions about how birds developed the ability to fly. Birds are not the only animals to have evolved this ability, but they are the only ones to use feathers for the airfoil needed to create lift. Thus the evolution of flight in birds depended on feathers. But since feathers serve other functions (such as display and insulation), it is not necessarily true that the evolution of feathers depended on flight. Feathers also could have developed initially to provide insulation to help maintain high body temperature. Warm bodies are required to sustain the kind of activity needed for flapping flight because the chemical reactions required to support rapid repetitive muscle contractions proceed most efficiently at higher temperatures. Thus feathers and the ability to maintain warm body temperatures metabolically (endothermy) were prerequisites for flapping flight in birds. But did birds start flying by flapping? There are two major lines of thought about how, and when, birds evolved the feathers and high internal body temperatures that allowed them to engage in flapping flight.
Paragraph 2 suggests which of the following about the evolution of feathers?
Inference Questions推理题
AFeathers first arose in animals living in warm climates
BFeathers arose in other flying animals before they arose in birds
CFeathers arose only after warm bodies arose.
DFeathers first arose for reasons other than flapping flight.
3
Questions regarding the ancestry of modern birds are closely linked to questions about how birds developed the ability to fly. Birds are not the only animals to have evolved this ability, but they are the only ones to use feathers for the airfoil needed to create lift. Thus the evolution of flight in birds depended on feathers. But since feathers serve other functions (such as display and insulation), it is not necessarily true that the evolution of feathers depended on flight. Feathers also could have developed initially to provide insulation to help maintain high body temperature. Warm bodies are required to sustain the kind of activity needed for flapping flight because the chemical reactions required to support rapid repetitive muscle contractions proceed most efficiently at higher temperatures. Thus feathers and the ability to maintain warm body temperatures metabolically (endothermy) were prerequisites for flapping flight in birds. But did birds start flying by flapping? There are two major lines of thought about how, and when, birds evolved the feathers and high internal body temperatures that allowed them to engage in flapping flight.
According to paragraph 2, why are high body temperatures necessary for flapping flight?
Factual Information Questions事实信息题
AHigh body temperatures are needed to create the airfoil required for lift.
BBodies tend to lose a lot of heat during flapping flight
CMuscles work most effectively at high body temperatures.
DHigh body temperatures encourage efficient feather growth.
4
The Trees-down Theory: For much of the twentieth century the conventional theory held that early birds were arboreal (tree dwelling) and that flight developed from gliding activities similar to those of flying squirrels, which take advantage of air currents as they leap from tree to tree by stretching out but not flapping their arms. According to this arboreal theory, feathers developed from early reptilian scales. The earliest protofeathers in this scenario were envisioned as arising from a genetic mutation that elongated or enlarged scales. Individuals with longer scales benefited because these scales would have increased the surface area of the outstretched forearms. which would have slowed the rate of fall and thus increased the distance of horizontal travel-when leaping from tree to tree. These advantages in turn, it is proposed, would have had survival benefits by reducing the risk of death from falling or from accidentally landing on the ground, where predators waited Further scale elaboration would have increased these advantages and longer, more aerodynamically shaped scales would have been selected for. Over the generations, as scales became more feather-like, short glides gave way to long ones, and gliding flight became possible. Simple gliders could have evolved into intermediate forms like Archaeopteryx, which may have supplemented gliding with weak flapping, and thence to modern birds with flapping flight Endothermy need not have arisen until the ancestors of birds were well differentiated from other reptiles and feathers were sufficiently elaborate to provide some insulating advantage. This theory was generated largely from the observation that Archaeopteryx had feet that could have grasped a branch. These grasping feet are taken as evidence that Archaeopteryx lived in trees. which makes the trees-down theory plausible.
Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.
Sentence Simplification Questions句子简化题
AIt was once thought that early birds gained the ability to move from tree to tree by using air currents at the same time that flying squirrels gained this ability.
BIt was long believed that early birds lived in trees and developed flight by gliding on air currents as flying squirrels do, stretching but not flapping their arms
CThe gliding activities of flying squirrels suggested the conventional theory that early birds moved from tree to tree without flapping
DBecause flying squirrels are arboreal creatures that can leap from tree to tree and take advantage of air currents, early birds were also thought to have been arboreal.
5
The Trees-down Theory: For much of the twentieth century the conventional theory held that early birds were arboreal (tree dwelling) and that flight developed from gliding activities similar to those of flying squirrels, which take advantage of air currents as they leap from tree to tree by stretching out but not flapping their arms. According to this arboreal theory, feathers developed from early reptilian scales. The earliest protofeathers in this scenario were envisioned as arising from a genetic mutation that elongated or enlarged scales. Individuals with longer scales benefited because these scales would have increased the surface area of the outstretched forearms. which would have slowed the rate of fall and thus increased the distance of horizontal travel-when leaping from tree to tree. These advantages in turn, it is proposed, would have had survival benefits by reducing the risk of death from falling or from accidentally landing on the ground, where predators waited Further scale elaboration would have increased these advantages and longer, more aerodynamically shaped scales would have been selected for. Over the generations, as scales became more feather-like, short glides gave way to long ones, and gliding flight became possible. Simple gliders could have evolved into intermediate forms like Archaeopteryx, which may have supplemented gliding with weak flapping, and thence to modern birds with flapping flight Endothermy need not have arisen until the ancestors of birds were well differentiated from other reptiles and feathers were sufficiently elaborate to provide some insulating advantage. This theory was generated largely from the observation that Archaeopteryx had feet that could have grasped a branch. These grasping feet are taken as evidence that Archaeopteryx lived in trees. which makes the trees-down theory plausible.
Why does the author include the information that the feet of Archaeopteryx “could have grasped a branch”?
Rhetorical Purpose Questions修辞目的题
ATo identify a feature that is viewed as support for the trees-down theory
BTo support the idea that the feathers of Archaeopteryx provided an insulating advantage
CTo support the claim that Archaeopteryx likely had evolved a warm body
DTo provide evidence that Archaeopteryx was already very different from reptiles
6
The Trees-down Theory: For much of the twentieth century the conventional theory held that early birds were arboreal (tree dwelling) and that flight developed from gliding activities similar to those of flying squirrels, which take advantage of air currents as they leap from tree to tree by stretching out but not flapping their arms. According to this arboreal theory, feathers developed from early reptilian scales. The earliest protofeathers in this scenario were envisioned as arising from a genetic mutation that elongated or enlarged scales. Individuals with longer scales benefited because these scales would have increased the surface area of the outstretched forearms. which would have slowed the rate of fall and thus increased the distance of horizontal travel-when leaping from tree to tree. These advantages in turn, it is proposed, would have had survival benefits by reducing the risk of death from falling or from accidentally landing on the ground, where predators waited Further scale elaboration would have increased these advantages and longer, more aerodynamically shaped scales would have been selected for. Over the generations, as scales became more feather-like, short glides gave way to long ones, and gliding flight became possible. Simple gliders could have evolved into intermediate forms like Archaeopteryx, which may have supplemented gliding with weak flapping, and thence to modern birds with flapping flight Endothermy need not have arisen until the ancestors of birds were well differentiated from other reptiles and feathers were sufficiently elaborate to provide some insulating advantage. This theory was generated largely from the observation that Archaeopteryx had feet that could have grasped a branch. These grasping feet are taken as evidence that Archaeopteryx lived in trees. which makes the trees-down theory plausible.
According to paragraph 3, how might tree-dwelling animals have benefited from a genetic mutation that lengthened or enlarged their scales?
Factual Information Questions事实信息题
AThey would have been better protected against the teeth of predators.
BThey would have been better hidden while in trees.
CThey would have been able to leap farther.
DThey would have been warmer.
7
The Ground-up Theory: In contrast, the ground-up, or terrestrial, theory posits that early birds were ground-dwelling, bipedal predators that chased down prey on foot and captured the victims with clawed forelimbs. This sort of behavior, like flapping flight, is best (though not exclusively) supported by a high body temperature. Warm-bodied predators can sustain the rapid repetitive muscle contractions used for running after prey for longer stretches of time than cold-bodied predators. Feathers may have developed for insulation, which would have improved the retention of body heat. Later. feathers might also have improved prey capture or balance while running by increasing the surface area of the extended forelimbs. As feathers enlarged. an airfoil developed, flight became possible and the advantages of flight drove further elaboration of feather structure. The ground-up idea arose from John Ostrom’s proposal linking Archaeopteryx to theropod dinosaurs which were apparently all active. terrestrial. bipedal predators and which increasingly are thought of as likely to have been able to maintain high body temperatures.
The word “retention” in the passage is closest in meaning to
Vocabulary Questions词汇题
Adistribution
Bproduction
Cuse
Dkeeping
8
The Ground-up Theory: In contrast, the ground-up, or terrestrial, theory posits that early birds were ground-dwelling, bipedal predators that chased down prey on foot and captured the victims with clawed forelimbs. This sort of behavior, like flapping flight, is best (though not exclusively) supported by a high body temperature. Warm-bodied predators can sustain the rapid repetitive muscle contractions used for running after prey for longer stretches of time than cold-bodied predators. Feathers may have developed for insulation, which would have improved the retention of body heat. Later. feathers might also have improved prey capture or balance while running by increasing the surface area of the extended forelimbs. As feathers enlarged. an airfoil developed, flight became possible and the advantages of flight drove further elaboration of feather structure. The ground-up idea arose from John Ostrom’s proposal linking Archaeopteryx to theropod dinosaurs which were apparently all active. terrestrial. bipedal predators and which increasingly are thought of as likely to have been able to maintain high body temperatures.
According to the ground-up theory as presented in paragraph 4, what advantage do warm-bodied animals have over cold-bodied animals?
Factual Information Questions事实信息题
AWarm-bodied animals can achieve better balance while running
BWarm-bodied animals can chase prey longer
CWarm-bodied animals can develop feathers.
DWarm-bodied animals can quickly increase the surface area of their forelimbs.
9
Debate over avian origins was stimulated in 1861 when the 150-million-year-old fossil of a bird-like creature was unearthed. [■] Called Archaeopteryx , it has feathers that are almost indistinguishable in form from modern flight feathers, yet it also has many reptilian features, including teeth. [■] Archaeopteryx seems to have been capable of some sort of aerial activity. [■] However, there is some debate over whether it was capable of powering itself through the air by flapping its wings. [■]
uestions regarding the ancestry of modern birds are closely linked to questions about how birds developed the ability to fly. Birds are not the only animals to have evolved this ability, but they are the only ones to use feathers for the airfoil needed to create lift. Thus the evolution of flight in birds depended on feathers. But since feathers serve other functions (such as display and insulation), it is not necessarily true that the evolution of feathers depended on flight. Feathers also could have developed initially to provide insulation to help maintain high body temperature. Warm bodies are required to sustain the kind of activity needed for flapping flight because the chemical reactions required to support rapid repetitive muscle contractions proceed most efficiently at higher temperatures. Thus feathers and the ability to maintain warm body temperatures metabolically (endothermy) were prerequisites for flapping flight in birds. But did birds start flying by flapping? There are two major lines of thought about how, and when, birds evolved the feathers and high internal body temperatures that allowed them to engage in flapping flight.
Look at the four squares [■] that indicate where the following sentence could be added to the passage
This combination of features makes Archaeopteryx a clear candidate for a transitional form between reptiles and modern birdsInsert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
The discovery of Archaeopteryx stimulated debate about the evolutionary origins of birds
Prose Summary Questions概要小结题
Select 3 answers
ABoth the trees-down theory and the ground-up theory of bird flight are based on findings suggesting that birds are descended from small, warm-bodied dinosaurs.
BAccording to one theory, early birds started out living in trees, evolved feathers that improved their gliding, and then developed endothermy and flapping flight.
CAccording to one theory, early birds were ground-dwelling predators who evolved feathers that improved their ability to stay warm and capture prey and were only later used for flight.
DBecause birds use their feathers for lift and because flapping flight requires a warm body, it seems likely that feathers and endothermy evolved before flapping flight did.
EAccording to one theory, early birds evolved from reptiles whose development of feathers and later development of flight enabled them to survive cold temperatures
FAccording to one theory, research showing that theropods had high body temperatures suggests that birds may have evolved flapping flight while still having very simple feathers
