TF阅读真题第844篇Climate Change and Species Distribution

Climate Change and Species Distribution

If temperature and moisture are the master limiting factors for the geographical ranges of plant and animal species, the climatic warming that is now occurring will have profound effects on Earth’s plant and animal life. One way to get a glimpse of the kinds of changes that may occur is to look back at the changes that have occurred in temperate regions since the end of the last ice age. A number of researchers have embarked on studies in this area, among them Margaret Davis, professor of ecology at the University of Minnesota.

After the last continental glaciers began retreating in North America and Eurasia about 16,000 years ago, the northward expansion of tree distributions lagged behind the retreat of the ice. A detailed record of these migrations is captured in fossilized pollen deposited in lakes and ponds. Over the past few decades, Professor Davis and her students have been leaders in deciphering the record of tree migration left in fossilized pollen deposits. In North America, oaks and maples moved rapidly in a northeasterly direction from the Mississippi Valley, while hickories advanced more slowly. Hemlocks and white pines moved rapidly northwest from refuges along the Atlantic coast. The important finding of this work is that the range of each species advanced individualistically. If you were sitting in New Hampshire, you would have seen sugar maple arrive in your area 9,000 years ago, hemlock 7,500 years ago, and beech 6,500 years ago.

If we can determine the climatic limits of current geographical distributions, we can make predictions about how distributions will change with climatic warming. A major assumption of using this approach for plants is that seed dispersal is adequate to sustain the projected migration of each species. The speed and distance at which trees of a given species disperse their seeds determines how quickly or slowly trees of that species can advance into a new area. Professor Davis has suggested that it was because of slow seed dispersal that it took 2， 500 years for hemlock to move north to its current range from where it was growing at the end of the last ice age.

Thanks to recent technological developments, computer models can now map the current and potential geographical range of any given plant species. If we use climate-change models to predict temperature and rainfall changes over the next 100 years, we can begin to gauge the size of the problem animals and plants will face over the next few centuries. As far as trees are concerned, climate-change models predict that the potential northern range limit of American beeches will move 700 to 900 kilometers north in the next century, and that the southern range limit will move to the north as well. If left to natural processes, beeches must move 7- 9 kilometers per year to the north. By contrast, since the end of the last ice age, beeches migrated into their present range at a rate of 0.2 kilometers per year. If what the models predict is even approximately correct, slowly colonizing species like trees will require human assistance to move into their new ranges. If this does not occur, species like beech may become extinct.

These effects of climate change will not appear immediately. Long-lived plant species such as trees will survive for many years as adults in inappropriate places. As the climate changes, their seed production will decline. Eventually, young trees will cease to grow in such areas. The effects of climate change are complicated by ecotypes–individuals of a species that show adaptations to their particular local temperature, moisture, or light levels that make them unable to survive under other conditions. The adaptations of ecotypes often have a genetic basis, and so in many cases, if an ecotype is transplanted to a new environment, its offspring acquire its characteristic adaptations even though in the new environment these features are not advantageous and may even be harmful. Ecotypic adaptation has often proceeded so far that one ecotype of a species cannot survive in the habitat of another ecotype of the same species. This poses a further difficulty for a population’s successful migration, since to survive, each ecotype within the population would need to migrate to and through areas that had the very specific climate to which it was adapted.

 

 

 

 

 

1

If temperature and moisture are the master limiting factors for the geographical ranges of plant and animal species, the climatic warming that is now occurring will have profound effects on Earth’s plant and animal life. One way to get a glimpse of the kinds of changes that may occur is to look back at the changes that have occurred in temperate regions since the end of the last ice age. A number of researchers have embarked on studies in this area, among them Margaret Davis, professor of ecology at the University of Minnesota.

The word “profound” in the passage is closest in meaning to

Avarious

Bserious

Charmful

Dpredictable

 

2

If temperature and moisture are the master limiting factors for the geographical ranges of plant and animal species, the climatic warming that is now occurring will have profound effects on Earth’s plant and animal life. One way to get a glimpse of the kinds of changes that may occur is to look back at the changes that have occurred in temperate regions since the end of the last ice age. A number of researchers have embarked on studies in this area, among them Margaret Davis, professor of ecology at the University of Minnesota.

According to paragraph 1, Margaret Davis has studied

Athe effects of moisture on plant species in cold regions

Bthe geographical ranges of plant and animal species before the last ice age

Cchanges in temperate parts of the world following the last ice age

Dfactors affecting the rate at which climate warming is now occurring

 

3

After the last continental glaciers began retreating in North America and Eurasia about 16,000 years ago, the northward expansion of tree distributions lagged behind the retreat of the ice. A detailed record of these migrations is captured in fossilized pollen deposited in lakes and ponds. Over the past few decades, Professor Davis and her students have been leaders in deciphering the record of tree migration left in fossilized pollen deposits. In North America, oaks and maples moved rapidly in a northeasterly direction from the Mississippi Valley, while hickories advanced more slowly. Hemlocks and white pines moved rapidly northwest from refuges along the Atlantic coast. The important finding of this work is that the range of each species advanced individualistically. If you were sitting in New Hampshire, you would have seen sugar maple arrive in your area 9,000 years ago, hemlock 7,500 years ago, and beech 6,500 years ago.

In paragraph 2, why does the author discuss the arrival dates in New Hampshire of different types of trees?

ATo provide evidence that the northward expansion of tree distribution lagged behind the retreat of glaciers

BTo contrast tree migration in New Hampshire with tree migration in other parts of North America

CTo illustrate the point that species migrated individualistically

DTo explain why Davis and her students decided to study fossilized pollen deposits

 

4

If we can determine the climatic limits of current geographical distributions, we can make predictions about how distributions will change with climatic warming. A major assumption of using this approach for plants is that seed dispersal is adequate to sustain the projected migration of each species. The speed and distance at which trees of a given species disperse their seeds determines how quickly or slowly trees of that species can advance into a new area. Professor Davis has suggested that it was because of slow seed dispersal that it took 2， 500 years for hemlock to move north to its current range from where it was growing at the end of the last ice age.

In paragraph 3, why does the author mention Davis’ explanation for the amount of time it took hemlock to move to its current range?

ATo support the idea that the rate of seed dispersal determines the rate of tree migration

BTo help explain why hemlock did not become extinct after the last ice age

CTo point out a weakness in a theory about rates of tree migration

DTo identify a method for calculating distribution changes resulting from climate warming

 

5

Thanks to recent technological developments, computer models can now map the current and potential geographical range of any given plant species. If we use climate-change models to predict temperature and rainfall changes over the next 100 years, we can begin to gauge the size of the problem animals and plants will face over the next few centuries. As far as trees are concerned, climate-change models predict that the potential northern range limit of American beeches will move 700 to 900 kilometers north in the next century, and that the southern range limit will move to the north as well. If left to natural processes, beeches must move 7- 9 kilometers per year to the north. By contrast, since the end of the last ice age, beeches migrated into their present range at a rate of 0.2 kilometers per year. If what the models predict is even approximately correct, slowly colonizing species like trees will require human assistance to move into their new ranges. If this does not occur, species like beech may become extinct.

The word “gauge” in the passage is closest in meaning to

Aestimate

Breveal

Creduce

Ddeal with

 

6

Thanks to recent technological developments, computer models can now map the current and potential geographical range of any given plant species. If we use climate-change models to predict temperature and rainfall changes over the next 100 years, we can begin to gauge the size of the problem animals and plants will face over the next few centuries. As far as trees are concerned, climate-change models predict that the potential northern range limit of American beeches will move 700 to 900 kilometers north in the next century, and that the southern range limit will move to the north as well. If left to natural processes, beeches must move 7- 9 kilometers per year to the north. By contrast, since the end of the last ice age, beeches migrated into their present range at a rate of 0.2 kilometers per year. If what the models predict is even approximately correct, slowly colonizing species like trees will require human assistance to move into their new ranges. If this does not occur, species like beech may become extinct.

According to paragraph 4, climate-change models predict that over the next 100 years, the geographical range of places suitable for beech trees will

Abecome smaller overall

Bchange at the rate of 0.2 kilometers a year

Creturn to conditions associated with the end of the last ice age

Dmove northward

 

7

These effects of climate change will not appear immediately. Long-lived plant species such as trees will survive for many years as adults in inappropriate places. As the climate changes, their seed production will decline. Eventually, young trees will cease to grow in such areas. The effects of climate change are complicated by ecotypes–individuals of a species that show adaptations to their particular local temperature, moisture, or light levels that make them unable to survive under other conditions. The adaptations of ecotypes often have a genetic basis, and so in many cases, if an ecotype is transplanted to a new environment, its offspring acquire its characteristic adaptations even though in the new environment these features are not advantageous and may even be harmful. Ecotypic adaptation has often proceeded so far that one ecotype of a species cannot survive in the habitat of another ecotype of the same species. This poses a further difficulty for a population’s successful migration, since to survive, each ecotype within the population would need to migrate to and through areas that had the very specific climate to which it was adapted.

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.

ABeing transplanted to a new environment can often lead ecotypes to develop new genetic adaptations that are then passed on to the ecotype’s offspring and become characteristic adaptations.

BOften a transplanted ecotype’s offspring will acquire the ecotype’s genetic adaptations even when those features provide no advantages or even are harmful in the new environment.

CAdaptations of ecotypes are often genetic, meaning that transplanting ecotype offspring to a new environment may not be advantageous and could even be harmful to the new environment.

DEven though the adaptations that ecotypes characteristically acquire and pass on to their offspring are often not advantageous in a new environment, many offspring can deal with their disadvantages.

 

8

These effects of climate change will not appear immediately. Long-lived plant species such as trees will survive for many years as adults in inappropriate places. As the climate changes, their seed production will decline. Eventually, young trees will cease to grow in such areas. The effects of climate change are complicated by ecotypes–individuals of a species that show adaptations to their particular local temperature, moisture, or light levels that make them unable to survive under other conditions. The adaptations of ecotypes often have a genetic basis, and so in many cases, if an ecotype is transplanted to a new environment, its offspring acquire its characteristic adaptations even though in the new environment these features are not advantageous and may even be harmful. Ecotypic adaptation has often proceeded so far that one ecotype of a species cannot survive in the habitat of another ecotype of the same species. This poses a further difficulty for a population’s successful migration, since to survive, each ecotype within the population would need to migrate to and through areas that had the very specific climate to which it was adapted.

Paragraph 5 implies which of the following about the ecotypes of trees as climate warming continues?

AThey will probably survive continuing climate warming because they will remain in their current habitats

BThey will develop new adaptations to temperature, moisture, and light preferences that allow them to survive in a wide range of conditions.

CMany will probably not be able to survive the process of migrating to a new range in response to continuing climate warming.

DMany will migrate to and successfully inhabit areas that they will share with other ecotypes of their species.

 

9

Thanks to recent technological developments, computer models can now map the current and potential geographical range of any given plant species. If we use climate-change models to predict temperature and rainfall changes over the next 100 years, we can begin to gauge the size of the problem animals and plants will face over the next few centuries. As far as trees are concerned, climate-change models predict that the potential northern range limit of American beeches will move 700 to 900 kilometers north in the next century, and that the southern range limit will move to the north as well. [■]If left to natural processes, beeches must move 7- 9 kilometers per year to the north. By contrast, since the end of the last ice age, beeches migrated into their present range at a rate of 0.2 kilometers per year.[■] If what the models predict is even approximately correct, slowly colonizing species like trees will require human assistance to move into their new ranges. [■]If this does not occur, species like beech may become extinct.[■]

Look at the four squaresthat indicate where the following sentence could be added to the passage

This difference between the historical and the predicated rates has important implications for the species’ survival.

Where would the sentence best fit？Click on a square  sentence to the passage.

10

One way scientists can predict the effects of modern climatic changes is to investigate the effects of past shifts in climate

AIn Europe and Eurasia, tree distributions began expanding soon after the last continental glaciers began retreating

BComputer estimates suggest that some species will be unable to migrate quickly enough using natural processes to avoid becoming extinct because of climate change.

CThe existence of ecotypes complicates the effects of climate change because one ecotype may require a different specific climate than another ecotype of the same species.

DStudies of fossilized pollen deposits show that tree species varied in the rate at which they expanded their range after the last ice age.

EA comparison of historical seed-dispersal rates and current seed-dispersal rates shows that the rates at which some species migrate have become more variable since the end of the last ice age.

FThe offspring of ecotypes are likely to acquire adaptations that will make them able to survive climate change by migrating to new ranges.