Were Dinosaurs Endothermic
题目：
Because dinosaurs are considered reptiles, they were for many years thought to be cold-blooded (ectothermic) like modern reptiles, requiring external heat sources such as sunlight, rather than warm-blooded (endothermic) like birds and mammals, which produce heat internally. But some scientists have argued otherwise, presenting several lines of evidence. First, some dinosaurs of the mid-to-late Mesozoic era (approximately 251-265 million years ago) had surface insulation, or at least they seemed to. For ectotherms, surface insulation would only block absorption of the sun’s rays and interfere with efficient basking (exposing themselves to sunlight). But for endotherms, a surface layer holding in internally generated heat would be an expected adaptation. Unfortunately, soft insulation is rarely preserved in fossils, but a few fossils of the Mesozoic were suggestive of an insulating layer that resembled hair in some dinosaurs and feathers in others. In fact, feathers likely first arose as thermal insulation and only later evolved into aerodynamic surfaces (helpful for flying). Some Mesozoic dinosaurs, then, appeared to have had surface insulation like that of endotherms rather than bare skin like that of ectotherms.
Second, large Mesozoic dinosaurs were found in temperate regions. Today, large reptiles such as great land tortoises and crocodiles do not occur in temperate regions-they live in warm tropical or subtropical climates. The only modern reptile inhabitants of temperate regions are small or slender turtles, lizards, and snakes. When winter arrives in temperate regions and freezing cold settles in, these small ectothermic reptiles squeeze themselves into deep crevices or small burrows where they safely hibernate until spring and escape the freezing temperatures of winter. On the other hand, for a large and bulky animal, there are no large cracks or crannies into which they can retreat to avoid the bite of winter cold. Large animals must be endothermic to survive in temperate climates. Thus, the presence of large reptiles in temperate climates of the Mesozoic suggests that they were warm-blooded.
The ratio(proportion) of predator species to prey species also argues for endothermic dinosaurs. Endotherms, in a sense, have their metabolic furnaces (the chemical processes that heat their bodies) turned up all the time, day in and day out, to hold a high body temperature. Therefore, compared to an equal-size ectothermic predator, an endothermic predator requires more “fuel” in the form of more prey to keep those chemical processes going. Paleontologist Robert Bakker reasoned that there should be few predators but lots of prey (lots of fuel to feed the few predators) in ecosystems dominated by endothermic reptiles. But if ectothermic reptiles dominated, then less heating fuel(prey) would be needed and so proportionately more predators would be present. Studying fossils from over millions of years, Bakker compiled predator-to-prey ratios. Comparing results over time, Bakker reasoned that the ratio of predators to prey should drop if dinosaurs were evolving an endothermic physiology. That seemed to happen. As the ratio was followed from early reptiles to predinosaurs to dinosaurs, it dropped. As the time horizon reaches dinosaurs, Bakker found proportionately fewer predator species and more prey species.
Moreover, the architecture of dinosaur bones seemed to be similar to that of endothermic mammals, not to that of ectothermic reptiles. Bones of ectothermic reptiles show annual growth rings like those of trees and for much the same reason: they grow in seasonal spurts. Endothermic mammals, with constant body temperature year-round, lack such growth rings in their bones. When various groups of dinosaurs were first examined, the microarchitecture of their bones seemed to tell a clear story-no growth rings.
Critics of this four-part case for warm-blooded dinosaurs challenge the various lines of evidence. They point out that insulating hair or feathers were present in very few Mesozoic reptiles and that the fossil record preserves no evidence of an insulating coat of feathers or hair in most dinosaurs. Similarly, fossils from so-called temperate regions may actually come from subtropical deposits or represent dinosaurs that migrated to mild climates during cold winter months. Calculations of predator-to-prey ratios, they note, are not so straightforward and may reflect unrepresentative or otherwise faulty fossil collection. Finally, a nearly constant body temperature may result from large body size alone; therefore, evidence from the microarchitecture of bone need not reflect an endothermic physiology.
1
Because dinosaurs are considered reptiles, they were for many years thought to be cold-blooded (ectothermic) like modern reptiles, requiring external heat sources such as sunlight, rather than warm-blooded (endothermic) like birds and mammals, which produce heat internally. But some scientists have argued otherwise, presenting several lines of evidence. First, some dinosaurs of the mid-to-late Mesozoic era (approximately 251-265 million years ago) had surface insulation, or at least they seemed to. For ectotherms, surface insulation would only block absorption of the sun’s rays and interfere with efficient basking (exposing themselves to sunlight). But for endotherms, a surface layer holding in internally generated heat would be an expected adaptation. Unfortunately, soft insulation is rarely preserved in fossils, but a few fossils of the Mesozoic were suggestive of an insulating layer that resembled hair in some dinosaurs and feathers in others. In fact, feathers likely first arose as thermal insulation and only later evolved into aerodynamic surfaces (helpful for flying). Some Mesozoic dinosaurs, then, appeared to have had surface insulation like that of endotherms rather than bare skin like that of ectotherms.
According to paragraph 1,insulation would be a problem for ectotherms for which of the following reasons?
Factual Information Questions事实信息题
AInsulation would interfere with ectotherms’ability to internally produce heat.
BInsulation would prevent ectotherms from taking in enough heat from sunlight.
CInsulation would prevent ectotherms from releasing absorbed heat.
DInsulation would result in ectotherms producing too much internally generated heat.
2
Because dinosaurs are considered reptiles, they were for many years thought to be cold-blooded (ectothermic) like modern reptiles, requiring external heat sources such as sunlight, rather than warm-blooded (endothermic) like birds and mammals, which produce heat internally. But some scientists have argued otherwise, presenting several lines of evidence. First, some dinosaurs of the mid-to-late Mesozoic era (approximately 251-265 million years ago) had surface insulation, or at least they seemed to. For ectotherms, surface insulation would only block absorption of the sun’s rays and interfere with efficient basking (exposing themselves to sunlight). But for endotherms, a surface layer holding in internally generated heat would be an expected adaptation. Unfortunately, soft insulation is rarely preserved in fossils, but a few fossils of the Mesozoic were suggestive of an insulating layer that resembled hair in some dinosaurs and feathers in others. In fact, feathers likely first arose as thermal insulation and only later evolved into aerodynamic surfaces (helpful for flying). Some Mesozoic dinosaurs, then, appeared to have had surface insulation like that of endotherms rather than bare skin like that of ectotherms.
According to paragraph 1， it is difficult to know whether dinosaurs of the mid-to-late Mesozoic had insulation because
Factual Information Questions事实信息题
Afew dinosaur fossils date back to the mid-to-late Mesozoic era
Bit is unclear whether surface layers found in fossils were hair or feathers
Cinsulating layers tend not to be preserved in the fossil record
Dfeathers were more likely used for flying than for insulation
3
Second, large Mesozoic dinosaurs were found in temperate regions. Today, large reptiles such as great land tortoises and crocodiles do not occur in temperate regions-they live in warm tropical or subtropical climates. The only modern reptile inhabitants of temperate regions are small or slender turtles, lizards, and snakes. When winter arrives in temperate regions and freezing cold settles in, these small ectothermic reptiles squeeze themselves into deep crevices or small burrows where they safely hibernate until spring and escape the freezing temperatures of winter. On the other hand, for a large and bulky animal, there are no large cracks or crannies into which they can retreat to avoid the bite of winter cold. Large animals must be endothermic to survive in temperate climates. Thus, the presence of large reptiles in temperate climates of the Mesozoic suggests that they were warm-blooded.
According to paragraph 2,why are large animals in temperate climates endothermic?
Factual Information Questions事实信息题
ABeing endothermic makes hibernating in winter easier for large animals.
BLarge animals do not have the ability to hide in small spaces to preserve heat.
CThe cracks and crannies into which large animals are able to retreat tend to remain cold.
DLarge animals are unable to migrate to tropical or subtropical climates in the winter.
4
The ratio(proportion) of predator species to prey species also argues for endothermic dinosaurs. Endotherms, in a sense, have their metabolic furnaces (the chemical processes that heat their bodies) turned up all the time, day in and day out, to hold a high body temperature. Therefore, compared to an equal-size ectothermic predator, an endothermic predator requires more “fuel” in the form of more prey to keep those chemical processes going. Paleontologist Robert Bakker reasoned that there should be few predators but lots of prey (lots of fuel to feed the few predators) in ecosystems dominated by endothermic reptiles. But if ectothermic reptiles dominated, then less heating fuel(prey) would be needed and so proportionately more predators would be present. Studying fossils from over millions of years, Bakker compiled predator-to-prey ratios. Comparing results over time, Bakker reasoned that the ratio of predators to prey should drop if dinosaurs were evolving an endothermic physiology. That seemed to happen. As the ratio was followed from early reptiles to predinosaurs to dinosaurs, it dropped. As the time horizon reaches dinosaurs, Bakker found proportionately fewer predator species and more prey species.
It can be inferred from paragraph 3 that, according to Robert Bakker, an ecosystem in which most of the predators are ectotherms would be associated with which of the following?
Inference Questions推理题
AProportionately more endothermic prey species than ectothermic prey species
BA decreasing number of predators over time
CPredators of smaller size than would be found in an ecosystem with many endothermic predators
DA smaller number of prey per predator than would be found in an ecosystem with many endothermic predators
5
Moreover, the architecture of dinosaur bones seemed to be similar to that of endothermic mammals, not to that of ectothermic reptiles. Bones of ectothermic reptiles show annual growth rings like those of trees and for much the same reason: they grow in seasonal spurts. Endothermic mammals, with constant body temperature year-round, lack such growth rings in their bones. When various groups of dinosaurs were first examined, the microarchitecture of their bones seemed to tell a clear story-no growth rings.
According to paragraph 4,which of the following types of animals generally develop growth rings?
Factual Information Questions事实信息题
AAnimals that live a very long time, like trees do
BAnimals that have very small bones
CAnimals that maintain a constant body temperature year-round
DAnimals that grow during a particular part of the year
6
Critics of this four-part case for warm-blooded dinosaurs challenge the various lines of evidence. They point out that insulating hair or feathers were present in very few Mesozoic reptiles and that the fossil record preserves no evidence of an insulating coat of feathers or hair in most dinosaurs. Similarly, fossils from so-called temperate regions may actually come from subtropical deposits or represent dinosaurs that migrated to mild climates during cold winter months. Calculations of predator-to-prey ratios, they note, are not so straightforward and may reflect unrepresentative or otherwise faulty fossil collection. Finally, a nearly constant body temperature may result from large body size alone; therefore, evidence from the microarchitecture of bone need not reflect an endothermic physiology.
The word “straightforward”in the passage is closest in meaning to
Vocabulary Questions词汇题
Asimple
Btypical
Cnecessary
Dwell accepted
7
Critics of this four-part case for warm-blooded dinosaurs challenge the various lines of evidence. They point out that insulating hair or feathers were present in very few Mesozoic reptiles and that the fossil record preserves no evidence of an insulating coat of feathers or hair in most dinosaurs. Similarly, fossils from so-called temperate regions may actually come from subtropical deposits or represent dinosaurs that migrated to mild climates during cold winter months. Calculations of predator-to-prey ratios, they note, are not so straightforward and may reflect unrepresentative or otherwise faulty fossil collection. Finally, a nearly constant body temperature may result from large body size alone; therefore, evidence from the microarchitecture of bone need not reflect an endothermic physiology.
The word “faulty” in the passage is closest in meaning to
Vocabulary Questions词汇题
Anot relevant
Bnot current
Cproblematic
Dcomplicated
8
Critics of this four-part case for warm-blooded dinosaurs challenge the various lines of evidence. They point out that insulating hair or feathers were present in very few Mesozoic reptiles and that the fossil record preserves no evidence of an insulating coat of feathers or hair in most dinosaurs. Similarly, fossils from so-called temperate regions may actually come from subtropical deposits or represent dinosaurs that migrated to mild climates during cold winter months. Calculations of predator-to-prey ratios, they note, are not so straightforward and may reflect unrepresentative or otherwise faulty fossil collection. Finally, a nearly constant body temperature may result from large body size alone; therefore, evidence from the microarchitecture of bone need not reflect an endothermic physiology.
Which of the following describes the purpose of paragraph 5 in the passage?
Rhetorical Purpose Questions修辞目的题
ATo argue that it is impossible to reach a conclusion about whether dinosaurs were endothermic or ectothermic
BTo summarize the findings presented in the first four paragraphs of the passage
CTo provide more recent evidence supporting the idea that dinosaurs were ectothermic
DTo explain why not all scientists agree that dinosaurs were warm-blooded
9
Second, large Mesozoic dinosaurs were found in temperate regions. [■] Today, large reptiles such as great land tortoises and crocodiles do not occur in temperate regions-they live in warm tropical or subtropical climates. [■] The only modern reptile inhabitants of temperate regions are small or slender turtles, lizards, and snakes. [■] When winter arrives in temperate regions and freezing cold settles in, these small ectothermic reptiles squeeze themselves into deep crevices or small burrows where they safely hibernate until spring and escape the freezing temperatures of winter. [■] On the other hand, for a large and bulky animal, there are no large cracks or crannies into which they can retreat to avoid the bite of winter cold. Large animals must be endothermic to survive in temperate climates. Thus, the presence of large reptiles in temperate climates of the Mesozoic suggests that they were warm-blooded.
Look at the four squares [■] that indicate where the following sentence could be added to the passage
The reason is easy to understand.
Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
There have been a number of challenges to the long-held idea that Mesozoic dinosaurs were ectothermic.
Prose Summary Questions概要小结题
Select 3 answers
ACold temperatures in the mid-to-late Mesozoic make it seem unlikely that large animals would have survived if they had been cold-blooded.
BMany scientists now suggest that dinosaurs may have made migrations from temperate to tropical or subtropical climates in winter to keep warm.
CDinosaur bones lack the growth rings characteristic of ectotherms, but this may be due to dinosaurs’ large size and is not necessarily proof that they were endotherms.
DDinosaurs may have had feathers or hair that would have provided surface insulation, but only a few fossils show evidence of this.
ECharacteristics of ecosystems where fossils of large dinosaurs were found, including a temperate climate and a large number of prey per predator, may indicate warm-bloodedness.
FConclusions drawn from the microarchitecture of bones from some large Mesozoic dinosaurs are not reliable because the samples may be unrepresentative of the population.
