问答题Practice 1　　Biological diversity, or biodiversity, means the variety of life on earth and includes the entire web of living organisms ranging from soil microbes, frogs, and trees to bears and blue whales. From the perspective of sustainable use, wildli

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第三篇

“Life Form Found" on Saturn ' s Titan

Scientists say they have discovered hints of alien life on the Saturn'5 moon.The discovery of a sort of
life was announced after researchers at the US space agency,NASA,analyzed data from spacecraft Cassini,
which pointed to the existence of methane-based form of life on Saturn's biggest moon.
Scientists have reportedly discovered clues showing primitive alien beings are"breathing"in Titan's
dense atmosphere filled with hydrogen.
They argue that hydrogen gets absorbed before hitting Titan's planet-like surface covered with methane
lakes and rivers.This,they say,points to the existence of some"bugs"consuming the hydrogen at the surface
of the moon less than half the size of the Earth.
"We suggested hydrogen consumption because it's the obvious gas for life to consume on Titan,similar
to the way we consume oxygen on Earth,"says NASA scientist Chris McKay."If these signs do turn out to be
a sign of life,it would be doubly exciting because it would represent a second form of life independent from
water-based life on Earth."
To date,scientists have not yet detected this form of life anywhere,though there are liquid-water-based
microorganisms on Earth that grow well on methane or produce it as a waste product. On Titan,where
temperatures are around minus 17 Kelvin(minus 290 degrees Farenheit),a methane-based organism would
have to use a substance that is liquid as its medium for living processes,but not water itself. Water is frozen
solid on Titan'5 surface and much too cold to support life as we know it.
Scientists had expected the Sun'5 interactions with chemicals in the atmosphere to produce a coating of
acetylene on Titan'5 surface.But Cassini detected no acetylene on the surface.
The absence of detectable acetylene on the Titan's surface can very well have a non-biological explana-
tion,said Mark Allen,a principal investigator of the NASA Titan team.
"Scientific conservatism suggests that a biological explanation should be the last choice after all non-
biological explanations are addressed,"Allen said."We have a lot of work to do to rule out possible non-bio-
logical explanations.It is more likely that a chemical process,without biology,can explain these results."

It can be inferred from Mark Allen's address that_____________.
A:scientists are trying to confirm these is life on Titan
B:scientists agree that a chemical process is a convincing explanation
C:scientists share the opinion that a biological explanation is reasonable
D:scientists are arguing over whether there is life on Titan

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To Survive or to Vanish

1.Over 3.6 billion years ago,the first creature was born in the world.Since then,the earth started its era with life.The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent,the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time,the opposite effect,in which life actually modifies its surroundings,has been relatively slight. Only in the present century has one species一man acquired significant power to alter the nature of his world.
2.During the past 25 years,this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air,earth,rivers,and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable.In this now universal contamination of the environment,chemicals are the sinister partners of radiation in changing the very nature of the world the very nature of its life. Chemicals sprayed on croplands or forests or gardens lie long in soil,entering into living organisms, passing from one to another in a chain of poisoning and death.Or they pass mysteriously by underground streams until they emerge and combine into new forms that kill vegetation,sicken cattle,and work unknown harm on those who drink from once pure wells."Man can hardly even recognize the devils of his own creation,"as a scientist has said.
3.Hundreds of millions of years have passed before the globe produced the life that now inhabits the earth.Given time not in years but in millennia life adjusts,and a balance has been reached.But in the modern world there is no time.
4.The quick steps of change follows the impetuous pace of man rather than the deliberate pace of nature.Radiation is now the unnatural creation of man's tampering with the atom.The chemicals are the synthetic creations of man's inventive mind,having no counterparts in nature.
5.To survive these chemicals would require not merely the years of one man's life but the life of generations.And even this,were it by some miracle possible,would be futile,for the new chemicals come from our laboratories in an endless stream;almost five hundred annually find their way into actual use in the United States alone.Among them are many that are used in man's war against nature.Since the mid l940's over 200 basic chemicals have been created for use in killing insects,weeds,and other organisms described as"pests".
6.It is not my contention that chemical insecticides must never he used.I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons,without their consent and often without their knowledge.I contend,furthermore,that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil,water,wildlife,and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life.

Human's pollution on nature is for the most part_______.
A:man's tampering with the atom
B:enormous numbers of people to contact with these poisons
C:the integrity of the natural world that supports all life
D:inventive
E:irrecoverable
F:relatively slight

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To Survive or to Vanish

1.Over 3.6 billion years ago,the first creature was born in the world.Since then,the earth started its era with life.The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent,the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time,the opposite effect,in which life actually modifies its surroundings,has been relatively slight. Only in the present century has one species一man acquired significant power to alter the nature of his world.
2.During the past 25 years,this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air,earth,rivers,and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable.In this now universal contamination of the environment,chemicals are the sinister partners of radiation in changing the very nature of the world the very nature of its life. Chemicals sprayed on croplands or forests or gardens lie long in soil,entering into living organisms, passing from one to another in a chain of poisoning and death.Or they pass mysteriously by underground streams until they emerge and combine into new forms that kill vegetation,sicken cattle,and work unknown harm on those who drink from once pure wells."Man can hardly even recognize the devils of his own creation,"as a scientist has said.
3.Hundreds of millions of years have passed before the globe produced the life that now inhabits the earth.Given time not in years but in millennia life adjusts,and a balance has been reached.But in the modern world there is no time.
4.The quick steps of change follows the impetuous pace of man rather than the deliberate pace of nature.Radiation is now the unnatural creation of man's tampering with the atom.The chemicals are the synthetic creations of man's inventive mind,having no counterparts in nature.
5.To survive these chemicals would require not merely the years of one man's life but the life of generations.And even this,were it by some miracle possible,would be futile,for the new chemicals come from our laboratories in an endless stream;almost five hundred annually find their way into actual use in the United States alone.Among them are many that are used in man's war against nature.Since the mid l940's over 200 basic chemicals have been created for use in killing insects,weeds,and other organisms described as"pests".
6.It is not my contention that chemical insecticides must never he used.I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons,without their consent and often without their knowledge.I contend,furthermore,that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil,water,wildlife,and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life.

Paragraph 1_______
A:Man should be cautious in chemical use.
B:It takes generations for mankind to adapt themselves to the chemicals.
C:Chemicals are human's invention
D:Human's power increases and has changed its character in the past quarter century.
E:The new change in the relationship between earth and its creature一human's power playing a greater role in changing the world
F: Modern world gives no time for nature to adjust to human.

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第一篇

Plant Gas

Scientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.
In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.
With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.
Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.
The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.

Which of the following about methane is not mentioned in the passage?
A:Plants growing in soil release methane.
B:Plants growing in water release methane.
C:Soil microbes consume methane.
D:Microbes in plants produce methane.

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第一篇

Plant Gas

Scientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.
In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.
With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.
Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.
The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.

Which statement is true of the methane emissions of plants in the experiment?
A:The lower the temperature,the higher the amount of methane emissions.
B:Living plants release less methane than dried plants at the same temperature.
C:When exposed to sunlight,plants stop releasing methane.
D:The higher the temperature,the greater the amount of methane emissions.

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第二篇

The Book of Life

So far, scientists have named about 1.8 million living species（物种）,and that's just a small part of
what probably exists on Earth.With so many plants,animals,and other creatures covering the planet,it can
be tough to figure out what type of spider is moving up your leg or what kind of bird is flying by.
A soon-to-be-launched Web site mighit help. An international team of researchers has announced the
creation of a Web-based Encyclopedia（百科全书）of Life(EoL).The project aims to catalog every species
on Earth in a single,easy-to-use referenice guide.
To get the encyclopedia started,the creators will use information from scientific databases（数据库）that
already exist. And eventually , in special sections of the site , nonscientists with specialized（专门的）
knowledge will get to join in Bird-watchers,for example,will be able to input which birds they'ye seen and
where.The technology for this kind of tool has only recently become available.
As the EoL develops,you might find it useful for school projects.The site will feature special pages for
kids who are studying ecosystems（生态系统）in their neighborhoods. To make sure the encyclopedia is
accurate,scientists will review much of the information added to it.People who visit the site will be able to
choose to leave out pages that haven't been reviewed.
Another convenient feature of the EoL is that you'11 be able to pick the level of detail you see to match
your interests,age,and current knowledge.If you wanted to learn about bears for a science class report,for
example,you could use the"novice"setting to get basic information about the animals.On the"expert"
setting,on the other hand,you could get much more detailed information about the history,literature,and
exploration of bears.
It now takes years for scientists to collect all the data they need to describe and analyze species.The
creators of the Encyclopedia of Life hope that their new tool will speed that process.

The goal of the creation of the EoL is to________.
A:collect enough data to analyze the living species on Earth
B:enlarge an existing Web site of the living species on Earth
C:work out an easy-to-use catalog of every living species on Earth
D:add new information to the existing databases of the living species on Earth

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第三篇

“Life Form Found" on Saturn ' s Titan

Scientists say they have discovered hints of alien life on the Saturn'5 moon.The discovery of a sort of
life was announced after researchers at the US space agency,NASA,analyzed data from spacecraft Cassini,
which pointed to the existence of methane-based form of life on Saturn's biggest moon.
Scientists have reportedly discovered clues showing primitive alien beings are"breathing"in Titan's
dense atmosphere filled with hydrogen.
They argue that hydrogen gets absorbed before hitting Titan's planet-like surface covered with methane
lakes and rivers.This,they say,points to the existence of some"bugs"consuming the hydrogen at the surface
of the moon less than half the size of the Earth.
"We suggested hydrogen consumption because it's the obvious gas for life to consume on Titan,similar
to the way we consume oxygen on Earth,"says NASA scientist Chris McKay."If these signs do turn out to be
a sign of life,it would be doubly exciting because it would represent a second form of life independent from
water-based life on Earth."
To date,scientists have not yet detected this form of life anywhere,though there are liquid-water-based
microorganisms on Earth that grow well on methane or produce it as a waste product. On Titan,where
temperatures are around minus 17 Kelvin(minus 290 degrees Farenheit),a methane-based organism would
have to use a substance that is liquid as its medium for living processes,but not water itself. Water is frozen
solid on Titan'5 surface and much too cold to support life as we know it.
Scientists had expected the Sun'5 interactions with chemicals in the atmosphere to produce a coating of
acetylene on Titan'5 surface.But Cassini detected no acetylene on the surface.
The absence of detectable acetylene on the Titan's surface can very well have a non-biological explana-
tion,said Mark Allen,a principal investigator of the NASA Titan team.
"Scientific conservatism suggests that a biological explanation should be the last choice after all non-
biological explanations are addressed,"Allen said."We have a lot of work to do to rule out possible non-bio-
logical explanations.It is more likely that a chemical process,without biology,can explain these results."

Which of the following can replace the title of this passage?
A:Different Life Form,a Possibility.
B:Earthlike Living Beings Found on Titan.
C:Finding of One More Moon of Saturn.
D:Titan,a New Satellite Discovered.

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第一篇

Plant Gas

Scientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.
In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.
With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.
Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.
The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.

What is the beneficial point of some microbes consuming plant-produced methane?
A:Methane becomes less poisonous.
B:Methane is turned into a fertilizer.
C:Less methane reaches the atmosphere.
D:Air becomes cleaner.

共用题干
To Survive or to Vanish

1.Over 3.6 billion years ago,the first creature was born in the world.Since then,the earth started its era with life.The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent,the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time,the opposite effect,in which life actually modifies its surroundings,has been relatively slight. Only in the present century has one species一man acquired significant power to alter the nature of his world.
2.During the past 25 years,this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air,earth,rivers,and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable.In this now universal contamination of the environment,chemicals are the sinister partners of radiation in changing the very nature of the world the very nature of its life. Chemicals sprayed on croplands or forests or gardens lie long in soil,entering into living organisms, passing from one to another in a chain of poisoning and death.Or they pass mysteriously by underground streams until they emerge and combine into new forms that kill vegetation,sicken cattle,and work unknown harm on those who drink from once pure wells."Man can hardly even recognize the devils of his own creation,"as a scientist has said.
3.Hundreds of millions of years have passed before the globe produced the life that now inhabits the earth.Given time not in years but in millennia life adjusts,and a balance has been reached.But in the modern world there is no time.
4.The quick steps of change follows the impetuous pace of man rather than the deliberate pace of nature.Radiation is now the unnatural creation of man's tampering with the atom.The chemicals are the synthetic creations of man's inventive mind,having no counterparts in nature.
5.To survive these chemicals would require not merely the years of one man's life but the life of generations.And even this,were it by some miracle possible,would be futile,for the new chemicals come from our laboratories in an endless stream;almost five hundred annually find their way into actual use in the United States alone.Among them are many that are used in man's war against nature.Since the mid l940's over 200 basic chemicals have been created for use in killing insects,weeds,and other organisms described as"pests".
6.It is not my contention that chemical insecticides must never he used.I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons,without their consent and often without their knowledge.I contend,furthermore,that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil,water,wildlife,and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life.

The effect of life modifying its surroundings has been_______.
A:man's tampering with the atom
B:enormous numbers of people to contact with these poisons
C:the integrity of the natural world that supports all life
D:inventive
E:irrecoverable
F:relatively slight

共用题干
To Survive or to Vanish

1.Over 3.6 billion years ago,the first creature was born in the world.Since then,the earth started its era with life.The history of life on earth has been a history of interaction between living things and their surroundings.To a large extent,the physical form and the habits of the earth's vegetation and its animal life have been molded by the environment. Considering the whole span of earthly time,the opposite effect,in which life actually modifies its surroundings,has been relatively slight. Only in the present century has one species一man acquired significant power to alter the nature of his world.
2.During the past 25 years,this power has not only become increasingly great but it has changed in character. The most alarming of all man's assaults upon the environment is the contamination of air,earth,rivers,and sea with dangerous and even lethal materials. This pollution is for the most part irrecoverable.In this now universal contamination of the environment,chemicals are the sinister partners of radiation in changing the very nature of the world the very nature of its life. Chemicals sprayed on croplands or forests or gardens lie long in soil,entering into living organisms, passing from one to another in a chain of poisoning and death.Or they pass mysteriously by underground streams until they emerge and combine into new forms that kill vegetation,sicken cattle,and work unknown harm on those who drink from once pure wells."Man can hardly even recognize the devils of his own creation,"as a scientist has said.
3.Hundreds of millions of years have passed before the globe produced the life that now inhabits the earth.Given time not in years but in millennia life adjusts,and a balance has been reached.But in the modern world there is no time.
4.The quick steps of change follows the impetuous pace of man rather than the deliberate pace of nature.Radiation is now the unnatural creation of man's tampering with the atom.The chemicals are the synthetic creations of man's inventive mind,having no counterparts in nature.
5.To survive these chemicals would require not merely the years of one man's life but the life of generations.And even this,were it by some miracle possible,would be futile,for the new chemicals come from our laboratories in an endless stream;almost five hundred annually find their way into actual use in the United States alone.Among them are many that are used in man's war against nature.Since the mid l940's over 200 basic chemicals have been created for use in killing insects,weeds,and other organisms described as"pests".
6.It is not my contention that chemical insecticides must never he used.I do contend that we have put poisonous and biologically potent chemicals indiscriminately into the hands of persons largely or wholly ignorant of their potentials for harm. We have subjected enormous numbers of people to contact with these poisons,without their consent and often without their knowledge.I contend,furthermore,that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil,water,wildlife,and man himself. Future generations are unlikely to forgive our lack of concern for the integrity of the natural world that supports all life.

Paragraph 5_______
A:Man should be cautious in chemical use.
B:It takes generations for mankind to adapt themselves to the chemicals.
C:Chemicals are human's invention
D:Human's power increases and has changed its character in the past quarter century.
E:The new change in the relationship between earth and its creature一human's power playing a greater role in changing the world
F: Modern world gives no time for nature to adjust to human.

共用题干
第一篇

Plant Gas

Scientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.
In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.
With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.
Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.
The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.

What was scientists' understanding of methane?
A:It was produced from plants.
B:It was not a greenhouse gas.
C:It was produced in oxygen-free environments.
D:It traps more heat than any other greenhouse gas.

共用题干
第一篇

Plant Gas

Scientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.
Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.
In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.
With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.
Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.
Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.
The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.

To test whether plants are a source of methane,the scientists created_______.
A:an oxygen-free environment
B:an environment with the same concentration of oxygen as the Earth has
C:a carbon dioxide-free environment
D:an environment filled with the greenhouse gas