TF阅读真题第849篇Azolla and Climate in the Arctic and Europe

Azolla and Climate in the Arctic and Europe

 

 

Climate in the Arctic and Europe has fluctuated over geologic time. The Arctic Ocean, which surrounds the North Pole, has not always been frigid and ice covered. Some 49 million years ago, it was more like the Black Sea in southeastern Europe today-with its oxygenless and very deep salty layer beneath fresher waters-though the Arctic Ocean was then more tropical than today’s Black Sea. This was also a time of intense rainfall, and as the formation of new continental landmasses caused the Arctic Ocean to become more cut off from the rest of the ocean, the runoff from rivers began to pool in its upper layers, which were freshened to the point that a particular kind of aquatic plant, known as Azolla, could grow there.

If you have ever lived near a pond, you will know Azolla, also known as pondweed, duckweed fern, or fairy moss. Its tiny, crinkly leaves often first appear as a minute speck of floating green that seems to increase slowly. But by the time it has covered 10 percent of the pond’s surface, it is only days away from a complete takeover. Given warmth and the right nutrients, Azolla can double its mass every three to ten days. The evidence that Azolla once grew in the Arctic Ocean is today buried beneath thousands of meters of frigid sediments and water below a skin of ice. It may have lain unrecognized forever were it not for some very expensive samples taken from deep in the Arctic sediments in 2004 by drill rig crews searching for oil. The last thing they expected to find was evidence of pondweed. But there it was-in layers of varying thickness distributed through at least eight vertical meters of sediment. The fossils were soon dubbed Azolla arctica. The presence of Azolla has now been confirmed in more than 100 drill cores taken from throughout the Arctic region, with the greatest concentrations being in samples drilled from the Arctic Ocean itself.

At least five species of Azolla were growing in and around the Arctic Ocean 49 million years ago. Warmth, fresh water, and the nutrients brought in from rivers provided all that the plants required. At its height, the Azolla bloom covered about 30 million square kilometers of ocean-an area the size of Africa. The plant grew so vigorously, sucking in atmospheric CO2 in the process, that it reduced the atmospheric concentration of CO2 (carbon dioxide) from at least 1,000 parts per million to 650. All that carbon, taken from the air and incorporated into the plant, would go on to form the Arctic oil reserves that the large oil companies are so keen to get to today. The Azolla blooms eventually extinguished themselves. CO2 in the atmosphere has a warming effect on Earth’s surface, and the lack of CO2 lowered global temperatures so substantially that rainfall declined at the poles, causing inflows of fresh water and nutrients to taper off, which starved the plant. As temperatures continued to drop, a layer of ice formed over the Arctic Ocean. Thus was a new icehouse world initiated by a minute plant. Initially, however, the lowering of CO2 concentrations had remarkably little effect on Europe-it was almost as if the preconditions for a major change had been established, but the trigger had yet to be pulled.

Europe’s climate finally cooled drastically about 34 million years ago. The trigger appears to have been the parting of the continent of South America from West Antarctica. The Drake Passage, as the seaway separating these landmasses is known, was initially shallow and remained so for millions of years, but water flow was sufficient to allow the establishment of an ocean current that encircled Antarctica. This allowed cold water to build up and an ice cap to form, which led to a fundamental reorganization of ocean currents and winds, bringing much cooler conditions. Studies of fossilized snail shells reveal that cold water exported into the North Atlantic from Antarctica caused air temperatures to drop by 4-6 degrees Celsius in southern Britain.

 

 

 

 

 

 

1

Climate in the Arctic and Europe has fluctuated over geologic time. The Arctic Ocean, which surrounds the North Pole, has not always been frigid and ice covered. Some 49 million years ago, it was more like the Black Sea in southeastern Europe today-with its oxygenless and very deep salty layer beneath fresher waters-though the Arctic Ocean was then more tropical than today’s Black Sea. This was also a time of intense rainfall, and as the formation of new continental landmasses caused the Arctic Ocean to become more cut off from the rest of the ocean, the runoff from rivers began to pool in its upper layers, which were freshened to the point that a particular kind of aquatic plant, known as Azolla, could grow there.

Paragraph 1 suggests that which of the following conditions was necessary for Azolla to grow in the Arctic Ocean?

AAn oxygenless and very deep salty layer like that of the Black Sea

BDecreased rainfall in the Arctic region

CRelatively low levels of salt in the upper layers of the Arctic Ocean

DThe entrance of Arctic Ocean water into the upper layers of rivers

 

2

If you have ever lived near a pond, you will know Azolla, also known as pondweed, duckweed fern, or fairy moss. Its tiny, crinkly leaves often first appear as a minute speck of floating green that seems to increase slowly. But by the time it has covered 10 percent of the pond’s surface, it is only days away from a complete takeover. Given warmth and the right nutrients, Azolla can double its mass every three to ten days. The evidence that Azolla once grew in the Arctic Ocean is today buried beneath thousands of meters of frigid sediments and water below a skin of ice. It may have lain unrecognized forever were it not for some very expensive samples taken from deep in the Arctic sediments in 2004 by drill rig crews searching for oil. The last thing they expected to find was evidence of pondweed. But there it was-in layers of varying thickness distributed through at least eight vertical meters of sediment. The fossils were soon dubbed Azolla arctica. The presence of Azolla has now been confirmed in more than 100 drill cores taken from throughout the Arctic region, with the greatest concentrations being in samples drilled from the Arctic Ocean itself.

Why does the author specify that”Given warmth and the right nutrients, Azolla can double its mass every three to ten days”?

Rhetorical Purpose Questions修辞目的题

ATo help explain why it is surprising that Azolla once grew in the Arctic Ocean

BTo explain why it is possible for Azolla to provide evidence of climate in the past

CTo explain how Azolla can quickly cover large areas even though it seems to spread slowly

DTo explain why the spread of Azolla in the Arctic Ocean was hidden by sediments and ice

3

If you have ever lived near a pond, you will know Azolla, also known as pondweed, duckweed fern, or fairy moss. Its tiny, crinkly leaves often first appear as a minute speck of floating green that seems to increase slowly. But by the time it has covered 10 percent of the pond’s surface, it is only days away from a complete takeover. Given warmth and the right nutrients, Azolla can double its mass every three to ten days. The evidence that Azolla once grew in the Arctic Ocean is today buried beneath thousands of meters of frigid sediments and water below a skin of ice. It may have lain unrecognized forever were it not for some very expensive samples taken from deep in the Arctic sediments in 2004 by drill rig crews searching for oil. The last thing they expected to find was evidence of pondweed. But there it was-in layers of varying thickness distributed through at least eight vertical meters of sediment. The fossils were soon dubbed Azolla arctica. The presence of Azolla has now been confirmed in more than 100 drill cores taken from throughout the Arctic region, with the greatest concentrations being in samples drilled from the Arctic Ocean itself.

According to paragraph 2， which of the following statements about Azolla in the Arctic is NOT true?

Negative Factual Information Questions否定事实信息题

AFossils of Azolla were discovered buried beneath sediment layers.

BIndividual Azolla plants grew to up to eight meters tall.

CAzolla grew in all parts of the Arctic region.

DThe heaviest concentrations of Azolla grew in the Arctic Ocean.

 

4

At least five species of Azolla were growing in and around the Arctic Ocean 49 million years ago. Warmth, fresh water, and the nutrients brought in from rivers provided all that the plants required. At its height, the Azolla bloom covered about 30 million square kilometers of ocean-an area the size of Africa. The plant grew so vigorously, sucking in atmospheric CO2 in the process, that it reduced the atmospheric concentration of CO2 (carbon dioxide) from at least 1,000 parts per million to 650. All that carbon, taken from the air and incorporated into the plant, would go on to form the Arctic oil reserves that the large oil companies are so keen to get to today. The Azolla blooms eventually extinguished themselves. CO2 in the atmosphere has a warming effect on Earth’s surface, and the lack of CO2 lowered global temperatures so substantially that rainfall declined at the poles, causing inflows of fresh water and nutrients to taper off, which starved the plant. As temperatures continued to drop, a layer of ice formed over the Arctic Ocean. Thus was a new icehouse world initiated by a minute plant. Initially, however, the lowering of CO2 concentrations had remarkably little effect on Europe-it was almost as if the preconditions for a major change had been established, but the trigger had yet to be pulled.

The word”preconditions”in the passage is closest in meaning to

Vocabulary Questions词汇题

Aforces

Bsigns

Cstructures

Drequirements

 

5

At least five species of Azolla were growing in and around the Arctic Ocean 49 million years ago. Warmth, fresh water, and the nutrients brought in from rivers provided all that the plants required. At its height, the Azolla bloom covered about 30 million square kilometers of ocean-an area the size of Africa. The plant grew so vigorously, sucking in atmospheric CO2 in the process, that it reduced the atmospheric concentration of CO2 (carbon dioxide) from at least 1,000 parts per million to 650. All that carbon, taken from the air and incorporated into the plant, would go on to form the Arctic oil reserves that the large oil companies are so keen to get to today. The Azolla blooms eventually extinguished themselves. CO2 in the atmosphere has a warming effect on Earth’s surface, and the lack of CO2 lowered global temperatures so substantially that rainfall declined at the poles, causing inflows of fresh water and nutrients to taper off, which starved the plant. As temperatures continued to drop, a layer of ice formed over the Arctic Ocean. Thus was a new icehouse world initiated by a minute plant. Initially, however, the lowering of CO2 concentrations had remarkably little effect on Europe-it was almost as if the preconditions for a major change had been established, but the trigger had yet to be pulled.

According to paragraph 3， Azolla blooms in the Arctic affected the climate by doing which of the following?

Factual Information Questions事实信息题

AAltering ocean currents by covering 30 million square kilometers of ocean

BAllowing Arctic oil reserves to release carbon dioxide into ocean waters

CReducing nutrients in ocean water from at least 1,000 parts per million to 650 parts per million

DAbsorbing a large amount of carbon dioxide from the atmosphere

 

6

At least five species of Azolla were growing in and around the Arctic Ocean 49 million years ago. Warmth, fresh water, and the nutrients brought in from rivers provided all that the plants required. At its height, the Azolla bloom covered about 30 million square kilometers of ocean-an area the size of Africa. The plant grew so vigorously, sucking in atmospheric CO2 in the process, that it reduced the atmospheric concentration of CO2 (carbon dioxide) from at least 1,000 parts per million to 650. All that carbon, taken from the air and incorporated into the plant, would go on to form the Arctic oil reserves that the large oil companies are so keen to get to today. The Azolla blooms eventually extinguished themselves. CO2 in the atmosphere has a warming effect on Earth’s surface, and the lack of CO2 lowered global temperatures so substantially that rainfall declined at the poles, causing inflows of fresh water and nutrients to taper off, which starved the plant. As temperatures continued to drop, a layer of ice formed over the Arctic Ocean. Thus was a new icehouse world initiated by a minute plant. Initially, however, the lowering of CO2 concentrations had remarkably little effect on Europe-it was almost as if the preconditions for a major change had been established, but the trigger had yet to be pulled.

According to paragraph 3， which of the following contributed to the disappearance of the Azolla blooms in the Arctic Ocean?

Factual Information Questions事实信息题

AFalling temperatures led to a decrease in Arctic rainfall that prevented Azolla from receiving enough nutrients and fresh water.

BA layer of ice developed over the rivers that had drained into the Arctic Ocean, cutting off Azolla’s supply of carbon.

CAzolla could no longer obtain the atmospheric carbon dioxide it needed to survive.

DAzolla plants became so numerous that they used up all of the available nutrients in the ocean.

 

7

Europe’s climate finally cooled drastically about 34 million years ago. The trigger appears to have been the parting of the continent of South America from West Antarctica. The Drake Passage, as the seaway separating these landmasses is known, was initially shallow and remained so for millions of years, but water flow was sufficient to allow the establishment of an ocean current that encircled Antarctica. This allowed cold water to build up and an ice cap to form, which led to a fundamental reorganization of ocean currents and winds, bringing much cooler conditions. Studies of fossilized snail shells reveal that cold water exported into the North Atlantic from Antarctica caused air temperatures to drop by 4-6 degrees Celsius in southern Britain.

The word”drastically”in the passage is closest in meaning to

Vocabulary Questions词汇题

Apermanently

Bslowly

Cvery greatly

Dinitially

 

8

Europe’s climate finally cooled drastically about 34 million years ago. The trigger appears to have been the parting of the continent of South America from West Antarctica. The Drake Passage, as the seaway separating these landmasses is known, was initially shallow and remained so for millions of years, but water flow was sufficient to allow the establishment of an ocean current that encircled Antarctica. This allowed cold water to build up and an ice cap to form, which led to a fundamental reorganization of ocean currents and winds, bringing much cooler conditions. Studies of fossilized snail shells reveal that cold water exported into the North Atlantic from Antarctica caused air temperatures to drop by 4-6 degrees Celsius in southern Britain.

According to paragraph 4， the opening of the Drake Passage resulted in all of the following EXCEPT

Negative Factual Information Questions否定事实信息题

Aocean waters near Antarctica becoming increasingly shallow over time

Bthe formation of an ocean current surrounding Antarctica

Can ice cap forming over Antarctica

Dcold water from Antarctica being transported to the North Atlantic

 

9

If you have ever lived near a pond, you will know Azolla, also known as pondweed, duckweed fern, or fairy moss. Its tiny, crinkly leaves often first appear as a minute speck of floating green that seems to increase slowly. But by the time it has covered 10 percent of the pond’s surface, it is only days away from a complete takeover. Given warmth and the right nutrients, Azolla can double its mass every three to ten days. The evidence that Azolla once grew in the Arctic Ocean is today buried beneath thousands of meters of frigid sediments and water below a skin of ice. [■]It may have lain unrecognized forever were it not for some very expensive samples taken from deep in the Arctic sediments in 2004 by drill rig crews searching for oil. [■]The last thing they expected to find was evidence of pondweed. [■]But there it was-in layers of varying thickness distributed through at least eight vertical meters of sediment. [■]The fossils were soon dubbed Azolla arctica. The presence of Azolla has now been confirmed in more than 100 drill cores taken from throughout the Arctic region, with the greatest concentrations being in samples drilled from the Arctic Ocean itself.

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

 

After all, conditions seemed hostile for most plant life.

Insert Text Questions句子插入题

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

 

10

The growth of Azolla in the Arctic affected climate conditions in the Arctic and Europe.

Prose Summary Questions概要小结题

Select 3 answers

AAzolla began to grow in the Arctic Ocean after it was cut off from the Black Sea in what is now southeastern Europe, leading to conditions that promoted the plant’s growth.

BScientists drilling cores in Arctic sediments were surprised to find fossils of Azolla because they believed the climate had been too cold to support the plant’s growth.

CFossils of snails that fed on Azolla demonstrate that Azolla continued to grow in Europe until its climate began to cool roughly 34 million years ago.

DAzolla growth occurred during a period when the Arctic was warm, and heavy rainfall entered rivers and built up fresh water on the surface of the Arctic Ocean.

EAzolla eventually covered such a large area that atmospheric CO2 levels dropped, causing temperatures to fall and creating conditions in which Arctic Azolla could no longer survive.

FEurope’s climate remained largely unaffected until Antarctica separated from South America, creating new wind and current patterns that led to colder conditions.