How Did Life Begin
For life to begin, it needed the right sorts of molecules, some sort of energy(such as that created by lightning), and the right environment-perhaps the “warm little pond” proposed by the great naturalist Charles Darwin. Further, the reactions that happened under these conditions, over time, must somehow have resulted in self-replicating molecules (molecules capable of producing copies of themselves). A famous experiment performed in 1953 by Stanley Miller and Harold Urey in fact created such possible conditions. It showed that a number of complex molecules could be formed in this way, especially amino acids, the building blocks of proteins and thus of life. However, life also would need some sort of protective membrane to form the precursor of living cells.
There now seems to be a growing consensus among scientists that chance reactions at one time long ago did, in fact, result in a cell membrane encasing a self-replicating molecule. But this still leaves the question: Where did it all happen? In a pond, as suggested by Darwin? Or in the sea? Earlier ideas held that because nearly all living things depend upon saline (salty) water in their cells, life probably evolved in the sea-somehow. One idea was that when tide pools evaporated, leaving briny soups, amino acids could have come together against some surface, such as tiny bubbles of air, and with sunlight providing the energy, a self-replicating biochemical system might have formed. That idea lost support when it was learned that the Sun’s ultraviolet radiation four billion years ago would have been too destructive for the complex molecules to have formed. Furthermore, the early oceans were probably constantly frozen over because the Sun was much weaker than it is today.
Today scientists are focused on the deep sea as the most likely environment for the initial evolution of life on Earth. In the late 1970s, deep submersibles investigating active undersea volcanoes came across areas where hot seawater, hotter than 350 degrees Celsius, was spewing out of cracks. The water was prevented from boiling because of the immense pressure at those depths, and it was rich in dissolved minerals that quickly precipitated out of solution upon encountering the cold surrounding waters, creating what have become known as “black smokers.” Entire biological communities were discovered that were being sustained by chemical energy from reactions involving hydrogen and carbon dioxide. These environments were common on the ancient seafloor at the time of the oceans’ first formation, and it is now thought that early life-forms first appeared here. Eventually these early life-forms led to modern forms that established themselves in shallower depths of the oceans. But as Darwin pointed out long ago, whatever did happen four billion years ago could not happen again today, at least not at the surface of the oceans, since life itself has changed the atmosphere and the oceans into a system not consistent with a new origin of life. We have too much oxygen in the atmosphere now.
Of course, the other idea is that life may have been brought to Earth long ago from outer space, as far-fetched as that may seem. The extraterrestrial hypothesis holds that life probably evolved first on Mars, and that a chunk of the Martian surface was blown into space by a large meteorite, and that eventually that chunk hit Earth as a meteorite, bringing with it some early protocell life-form. An attractive aspect of this hypothesis is that life would not have to have evolved independently on separate planets, but only once, somewhere in the solar system, and then spread from there. Support for this idea came several years ago when a Martian meteorite found in Antarctica was analyzed and found to have evidence of primitive life. More recently, in 2009, NASA scientists announced that they had found, for the first time, the amino acid glycine in material collected by the Stardust space probe from the tail of a comet. These findings and the various conclusions that were offered, however, remain very controversial.
题目：
1
For life to begin, it needed the right sorts of molecules, some sort of energy(such as that created by lightning), and the right environment-perhaps the “warm little pond” proposed by the great naturalist Charles Darwin. Further, the reactions that happened under these conditions, over time, must somehow have resulted in self-replicating molecules (molecules capable of producing copies of themselves). A famous experiment performed in 1953 by Stanley Miller and Harold Urey in fact created such possible conditions. It showed that a number of complex molecules could be formed in this way, especially amino acids, the building blocks of proteins and thus of life. However, life also would need some sort of protective membrane to form the precursor of living cells.
According to paragraph 1, the experiment performed in 1953 by Stanley Miller and Harold Urey showed that
Factual Information Questions事实信息题
ADarwin’s idea that life began in a “warm little pond” was incorrect
Bproteins play a more significant role than amino acids in building life
Cmolecules that produce copies of themselves can form if the right conditions are present
Dformation of protective membranes occurs before formation of amino acids
2
There now seems to be a growing consensus among scientists that chance reactions at one time long ago did, in fact, result in a cell membrane encasing a self-replicating molecule. But this still leaves the question: Where did it all happen? In a pond, as suggested by Darwin? Or in the sea? Earlier ideas held that because nearly all living things depend upon saline (salty) water in their cells, life probably evolved in the sea-somehow. One idea was that when tide pools evaporated, leaving briny soups, amino acids could have come together against some surface, such as tiny bubbles of air, and with sunlight providing the energy, a self-replicating biochemical system might have formed. That idea lost support when it was learned that the Sun’s ultraviolet radiation four billion years ago would have been too destructive for the complex molecules to have formed. Furthermore, the early oceans were probably constantly frozen over because the Sun was much weaker than it is today.
Why does the author note that”the early oceans were probably constantly frozen over”?
Rhetorical Purpose Questions修辞目的题
ATo cast doubt on the idea that life could have begun on Earth four billion years ago
BTo support the idea that the Sun was much weaker four billion years ago than it is today
CTo provide additional evidence against the idea that life originated in tide pools
DTo point out why Darwin thought that life began in a pond, rather than in the sea
3
There now seems to be a growing consensus among scientists that chance reactions at one time long ago did, in fact, result in a cell membrane encasing a self-replicating molecule. But this still leaves the question: Where did it all happen? In a pond, as suggested by Darwin? Or in the sea? Earlier ideas held that because nearly all living things depend upon saline (salty) water in their cells, life probably evolved in the sea-somehow. One idea was that when tide pools evaporated, leaving briny soups, amino acids could have come together against some surface, such as tiny bubbles of air, and with sunlight providing the energy, a self-replicating biochemical system might have formed. That idea lost support when it was learned that the Sun’s ultraviolet radiation four billion years ago would have been too destructive for the complex molecules to have formed. Furthermore, the early oceans were probably constantly frozen over because the Sun was much weaker than it is today.
Paragraph 2 suggests that, based on current knowledge, self-replicating molecules probably first formed in a place that
Inference Questions推理题
Awas protected from sunlight
Blacked salt
Cprovided access to a large amount of fresh air
Dhad a large amount of ice available
4
Today scientists are focused on the deep sea as the most likely environment for the initial evolution of life on Earth. In the late 1970s, deep submersibles investigating active undersea volcanoes came across areas where hot seawater, hotter than 350 degrees Celsius, was spewing out of cracks. The water was prevented from boiling because of the immense pressure at those depths, and it was rich in dissolved minerals that quickly precipitated out of solution upon encountering the cold surrounding waters, creating what have become known as “black smokers.” Entire biological communities were discovered that were being sustained by chemical energy from reactions involving hydrogen and carbon dioxide. These environments were common on the ancient seafloor at the time of the oceans’ first formation, and it is now thought that early life-forms first appeared here. Eventually these early life-forms led to modern forms that established themselves in shallower depths of the oceans. But as Darwin pointed out long ago, whatever did happen four billion years ago could not happen again today, at least not at the surface of the oceans, since life itself has changed the atmosphere and the oceans into a system not consistent with a new origin of life. We have too much oxygen in the atmosphere now.
The word “immense” in the passage is closest in meaning to
Vocabulary Questions词汇题
Avariable
Bunusual
Cconstant
Denormous
5
Today scientists are focused on the deep sea as the most likely environment for the initial evolution of life on Earth. In the late 1970s, deep submersibles investigating active undersea volcanoes came across areas where hot seawater, hotter than 350 degrees Celsius, was spewing out of cracks. The water was prevented from boiling because of the immense pressure at those depths, and it was rich in dissolved minerals that quickly precipitated out of solution upon encountering the cold surrounding waters, creating what have become known as “black smokers.” Entire biological communities were discovered that were being sustained by chemical energy from reactions involving hydrogen and carbon dioxide. These environments were common on the ancient seafloor at the time of the oceans’ first formation, and it is now thought that early life-forms first appeared here. Eventually these early life-forms led to modern forms that established themselves in shallower depths of the oceans. But as Darwin pointed out long ago, whatever did happen four billion years ago could not happen again today, at least not at the surface of the oceans, since life itself has changed the atmosphere and the oceans into a system not consistent with a new origin of life. We have too much oxygen in the atmosphere now.
Which of the following can be inferred about the discovery of “biological communities”in the deep sea?
Rhetorical Purpose Questions修辞目的题
AIt provides support for the idea that the first life-forms appeared in similar environments on the ancient seafloor.
BIt proves that these communities will eventually establish themselves in shallower depths of the oceans.
CIt indicates that energy from chemical reactions protects these life-forms from the dangerous effects of undersea volcanoes.
DIt suggests that conditions in the oceans may not have changed as much since ancient times as scientists once believed.
6
Today scientists are focused on the deep sea as the most likely environment for the initial evolution of life on Earth. In the late 1970s, deep submersibles investigating active undersea volcanoes came across areas where hot seawater, hotter than 350 degrees Celsius, was spewing out of cracks. The water was prevented from boiling because of the immense pressure at those depths, and it was rich in dissolved minerals that quickly precipitated out of solution upon encountering the cold surrounding waters, creating what have become known as “black smokers.” Entire biological communities were discovered that were being sustained by chemical energy from reactions involving hydrogen and carbon dioxide. These environments were common on the ancient seafloor at the time of the oceans’ first formation, and it is now thought that early life-forms first appeared here. Eventually these early life-forms led to modern forms that established themselves in shallower depths of the oceans. But as Darwin pointed out long ago, whatever did happen four billion years ago could not happen again today, at least not at the surface of the oceans, since life itself has changed the atmosphere and the oceans into a system not consistent with a new origin of life. We have too much oxygen in the atmosphere now.
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
AWhatever happened four billion years ago resulted in changes to the atmosphere and oceans that made them into a very different kind of system than they were before.
BDarwin pointed out that whatever happened at the surface of the oceans four billion years ago resulted in a system that was not consistent with life’s origin there.
CThe presence of life has changed the atmosphere and the oceans in ways that now make a new origin of life, especially at the surface of the oceans, impossible.
DDarwin was right when he pointed out long ago that life in the atmosphere and the oceans has changed greatly from the way it was four billion years ago.
7
Of course, the other idea is that life may have been brought to Earth long ago from outer space, as far-fetched as that may seem. The extraterrestrial hypothesis holds that life probably evolved first on Mars, and that a chunk of the Martian surface was blown into space by a large meteorite, and that eventually that chunk hit Earth as a meteorite, bringing with it some early protocell life-form. An attractive aspect of this hypothesis is that life would not have to have evolved independently on separate planets, but only once, somewhere in the solar system, and then spread from there. Support for this idea came several years ago when a Martian meteorite found in Antarctica was analyzed and found to have evidence of primitive life. More recently, in 2009, NASA scientists announced that they had found, for the first time, the amino acid glycine in material collected by the Stardust space probe from the tail of a comet. These findings and the various conclusions that were offered, however, remain very controversial.
The word “controversial” in the passage is closest in meaning to
Vocabulary Questions词汇题
Ainadequate
Bdebatable
Cunsatisfactory
Dhypothetical
8
Of course, the other idea is that life may have been brought to Earth long ago from outer space, as far-fetched as that may seem. The extraterrestrial hypothesis holds that life probably evolved first on Mars, and that a chunk of the Martian surface was blown into space by a large meteorite, and that eventually that chunk hit Earth as a meteorite, bringing with it some early protocell life-form. An attractive aspect of this hypothesis is that life would not have to have evolved independently on separate planets, but only once, somewhere in the solar system, and then spread from there. Support for this idea came several years ago when a Martian meteorite found in Antarctica was analyzed and found to have evidence of primitive life. More recently, in 2009, NASA scientists announced that they had found, for the first time, the amino acid glycine in material collected by the Stardust space probe from the tail of a comet. These findings and the various conclusions that were offered, however, remain very controversial.
Which of the following is presented in paragraph 4 as evidence that life may have evolved only once in the solar system and spread from there?
Factual Information Questions事实信息题
AA Martian meteorite containing evidence of primitive life
BThe discovery by the Stardust space probe of an early proto-cell life-form on Mars
CEvidence that a chunk of Mars was blown into space by a large meteorite
DThe absence of life on Earth before it was hit by a meteorite from Mars
9
For life to begin, it needed the right sorts of molecules, some sort of energy(such as that created by lightning), and the right environment-perhaps the “warm little pond” proposed by the great naturalist Charles Darwin. Further, the reactions that happened under these conditions, over time, must somehow have resulted in self-replicating molecules (molecules capable of producing copies of themselves). A famous experiment performed in 1953 by Stanley Miller and Harold Urey in fact created such possible conditions. [■]It showed that a number of complex molecules could be formed in this way, especially amino acids, the building blocks of proteins and thus of life. [■]However, life also would need some sort of protective membrane to form the precursor of living cells. [■]
There now seems to be a growing consensus among scientists that chance reactions at one time long ago did, in fact, result in a cell membrane encasing a self-replicating molecule. [■]But this still leaves the question: Where did it all happen? In a pond, as suggested by Darwin? Or in the sea? Earlier ideas held that because nearly all living things depend upon saline (salty) water in their cells, life probably evolved in the sea-somehow. One idea was that when tide pools evaporated, leaving briny soups, amino acids could have come together against some surface, such as tiny bubbles of air, and with sunlight providing the energy, a self-replicating biochemical system might have formed. That idea lost support when it was learned that the Sun’s ultraviolet radiation four billion years ago would have been too destructive for the complex molecules to have formed. Furthermore, the early oceans were probably constantly frozen over because the Sun was much weaker than it is today.
Look at the four squares [■] that indicate where the following sentence could be added to the passage
And this was not created in the experiment.Insert Text Questions句子插入题
Where would the sentence best fit？Click on a square sentence to the passage.
10
Life cannot begin without an energy source, a suitable environment, and certain kinds of molecules.
Prose Summary Questions概要小结题
Select 3 answers
AAt first scientists disagreed with Darwin that life could originate in a pond, but recent evidence suggests that Darwin may have been right.
BThe idea that life evolved in the sea lost support when scientists realized that tide pools lacked essential amino acids present in most living cells.
CSome think that primitive life may have first originated elsewhere in the solar system and then arrived on Earth long ago via meteorites.
DIt was once thought that life originated in tide pools in which the water had dried up, but this idea was eventually abandoned, in part because the Sun was weaker when life began than it is today.
EToday many scientists believe that the earliest life-forms were sustained by chemical reactions around undersea volcanoes, where hot water, cold water, and minerals interacted.
FThe extraterrestrial hypothesis resulted from the realization that Earth’s atmosphere and oceans contain too much oxygen to make Earth a suitable environment for life to originate.
