閱讀理解真題解析：Alaska and Bark Beetles阿拉斯加和樹皮甲蟲

託福閱讀理解真題解析：

託福閱讀理解真題

Over the twentieth century， global temperatures increased by an average of about 0。7 degrees Celsius， but some places have warmed a lot more than this， and other places have warmed less。 These temperature increases have been enough to trigger changes in ecosystems all over the world， especially in places where the warming has been the greatest。 In some places， the changes have been

解析：

， perhaps a slight shift in vegetation that only a careful observer would notice。 In other cases， small changes in climate have sparked a chain of larger effects， leading to massive changes。

The biggest climate-caused ecosystem shifts today are happening at the world‘s most northern latitudes， where the temperature over the last century has been rising about two times faster than the global average。 In the northernmost state of the United States， Alaska， for example， warming has paved the way for a spike in the numbers of spruce bark beetles。 Bark beetles have been a pest to Alaskan white spruce trees for thousands of years， but their numbers were held in check by the cold climate， which forced the insects to hide in the bark of individual trees for most of the year。 As the length of the warm season increased over the 1980s and 1990s， however， bark beetles had more time to fly from one tree to the next， burrow， and lay their eggs between the bark and the wood。 The beetles had another thing going for them， too： a multi-year drought had weakened many of the spruce trees， leaving them vulnerable to attack。 In the mid-1990s， the bark beetle population exploded， and over the next few years the pests wiped out white spruce forests over an area the size of the U。S。 state of Connecticut。 In the years since， the combined forces of a longer insect-breeding season and forest management practices that left forests overcrowded gave way to similar epidemics farther south。 Large swaths of pine and spruce have been destroyed by insects in several other parts of the United States。

In the late 1990s， the effects of the bark beetle epidemic rippled throughout Alaska’s white spruce ecosystem and affected virtually every population of living organisms， but not all of the impacts were negative。 Fewer spruce trees meant a sunnier area in the forest below the treetops， which allowed grasses to move in and take hold。 The grasses， in turn， changed the soil temperature， making the environment more friendly for some other types of vegetation。 Animals that feed on grasses， including moose， elk， and some birds， also benefited。 But the beetle infestation was bad news for organisms that rely on white spruce for their habitat， like hawks， owls， red squirrels， and voles。 Volesa type of small， mouselike rodentare an especially vital part of the ecosystem because they help spread mycorrhizal fungi， which attach to the roots of plants and help them take in water and nutrients。 Voles are also an important food for a number of predators。

Ecosystem changes always hurt some living creatures and help others。 ［▇］ It‘s hard to say， therefore， whether a change is good or bad overall。 ［▇］ Instead， ecologists （people who study ecosystems） often focus on the impacts on a single species： for instance， us。 ［▇］ In the short term， the Alaskan spruce beetle epidemic supplied a lot of people with firewood， but only by destroying tons of otherwise valuable timber and threatening the livelihoods of loggers。 And no one knows for sure what the long-term impacts on the forest will be。 Ecosystems tend to return to their previous states after disturbances like pest outbreaks， fires， or major storm events， but if the Alaskan spruce ecosystem is disturbed too often or too much， it might shift to a different type of forest， a woodland， or a grassland instead。 ［▇］

In extreme cases， major assaults on ecosystems can lead to a total collapse in which the ecosystem doesn’t bounce back to the way it was or transition to a new， healthy state。 The result is an area with very little life； in the oceans， biologists refer to these areas as dead zones。 One such example is the coral reef die-off that happened in the Indian Ocean in the late 1990s。

Alaska and Bark Beetles

subtle

A。to limited

B。unimportant

C。not obvious

D。gradual

1.

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

A。By making it possible for a beetle to deposit its eggs in a greater number of trees

B。By making it possible for beetles to survive in the bark of trees for longer lengths of time

C。By making it unnecessary for a beetle to protect its eggs by laying them between the bark and the wood

D。By increasing the number of spruce trees， thereby providing the beetles with far more places to live

2.

A。Paragraph 2 explains the causes of the spruce bark beetle epidemic in Alaska， and paragraph 3 discusses the chain of events that occurred as a result of that epidemic。

B。Paragraph 2 shows that warming air temperatures can affect a large number of species， and paragraph 3 shows that warming soil temperatures can have even greater effects。

C。Paragraph 2 discusses one explanation for the disappearance of spruce trees from a part of Alaska， but paragraph 3 shows that an alternative explanation is more likely to be correct。

D。Paragraph 2 describes the negative consequences of climate warming for some species， but paragraph 3 shows that there are also some positive consequences for these same species。

Paragraph 2 suggests that the warming of the Alaskan climate affected bark beetles in which of the following ways

3.Which of the following statements most accurately describes the relationship of paragraph 3 to paragraph 2

A。The epidemic increased the availability of water for these animals。

B。The epidemic increased the availability of food for these animals。

C。The epidemic destroyed the habitat of these animals。

D。The epidemic meant that these animals experienced more competition from hawks， owls， red squirrels， and voles。

4.

A。Some predators may have less to eat。

B。Hawk and red squirrel populations may be more successful。

C。Plants may find it more difficult to absorb water and nutrients。

D。Mycorrhizal fungi numbers may increase。

According to paragraph 3, which of the following effects did the bark beetle epidemic have on moose, elk, and some birds

5.According to paragraph 3, a decline in the vole population in Alaska may have which TWO of the following consequences To receive credit, you must select TWO answer choices.

A。Ecosystems like the spruce ecosystem in Alaska tend to return to their previous states after disturbances such as pest outbreaks， fires， or major storm events。

B。While ecosystems tend to return to their previous states after disturbances， the Alaskan spruce ecosystem might not if it is disturbed too often or too much。

C。Ecosystems tend to return to their previous states after disturbances， so Alaska might again become covered with woodlands or grasslands。

D。After certain types of disturbances such as pest outbreaks， ecosystems do not always return to their previous states but shift to being woodlands or grasslands instead。

6.

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.

A。Ecosystems that totally collapsed

B。Ecosystems that transitioned to a new， healthy state

C。Ecosystems that bounced back to the way they were

D。Ecosystems that were affected by a nearby dead zone

7.

In paragraph 5, coral reefs in the Indian Ocean are presented as an example of which of the following

A。Why has the temperature at northern latitudes been rising faster than the global average

B。Why did corals in the Indian Ocean die off in the late 1990s

C。What types of vegetation benefited from the change in soil temperatures in Alaska

D。What were some of the effects of the bark beetle epidemic for humans

9。Look at the four squares［▇］ that indicate where the following sentence could be added to the passage。 Where would the sentence best fit？

8.

10。Directions：

An introductory sentence for a brief summary of the passage is provided below。 Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage。 Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage。 This questions is worth 2 points。

A。Global warming has led to changes in ecosystems all over the world， with ecosystems at northern latitudes being affected the most。

B。A longer warm season in Alaska caused a sharp increase in the number of bark beetles， leading to the destruction of spruce forests， which in turn seriously affected many other species。

C。Sometimes ecosystems are able to recover from disturbances or to develop into different， but healthy， systems， but in extreme cases， they may collapse completely。

D。The loss of spruce forests caused an epidemic in mycorrhizal fungi， and these fungi damaged the roots of many plants， making them unable to take in water and nutrients。

E。Whereas some types of changes are good for the majority of species in an ecosystem， ecologists believe that most disturbances to ecosystems are bad overall。

F。Coral reefs may die off as a result of the global increase in temperatures， but after a transition period as a dead zone， they are able to return to their original state。

The passage provides an answer to which of the following questions

But even from this limited perspective, the answer is not completely straightforward.

Alaska and Bark Beetles

在二十世紀，全球溫度平均升高了約0。7攝氏度，但有些地方的升溫幅度超過此數值，而其他地方的升溫幅度較小。這些溫度升高足以觸發全世界生態系統的變化，尤其是在變暖最大的地方。在某些地方，變化微妙，也許只有細心的觀察者才會注意到植被的輕微變化。在其他情況下，氣候的微小變化引發了一系列更大的影響，導致了巨大的變化。

今天，由氣候引起的最大的生態系統變化發生在世界最北部的緯度地區，上個世紀的溫度上升速度是全球平均水平的兩倍左右。例如，在美國最北端的阿拉斯加，變暖為雲杉樹皮甲蟲數量激增鋪平了道路。幾千年來，樹皮甲蟲一直是阿拉斯加白雲杉樹的害蟲，但由於寒冷的氣候，樹皮甲蟲的數量一直受到控制，這迫使昆蟲在一年中的大部分時間都藏在個別樹的樹皮中。然而，隨著1980年代和1990年代溫暖季節的延長，樹皮甲蟲有更多的時間從一棵樹飛到另一棵樹，挖穴，並在樹皮和木頭之間產卵。甲蟲也有另一件事：多年的乾旱削弱了許多雲杉樹木，使它們容易受到攻擊。在1990年代中期，樹皮甲蟲數量激增，在接下來的幾年中，蟲害席捲了美國康涅狄格州大小的白雲杉林。此後的幾年中，更長的昆蟲繁殖季節和森林管理實踐共同導致了森林過度擁擠的局面，被更南端的類似流行病所取代。在美國其他幾個地方，大片的松樹和雲杉被昆蟲破壞了。漫長的昆蟲繁殖季節和森林管理實踐的共同作用，使森林擁擠不堪，而更南端的類似流行病也讓位於。在美國其他幾個地方，大片的松樹和雲杉被昆蟲破壞了。漫長的昆蟲繁殖季節和森林管理實踐的共同作用，使森林擁擠不堪，而更南端的類似流行病也讓位於。在美國其他幾個地方，大片的松樹和雲杉被昆蟲破壞了。

在1990年代後期，樹皮甲蟲流行的影響波及整個阿拉斯加的白雲杉生態系統，並幾乎影響了所有活生物體，但並非所有影響都是負面的。較少的雲杉樹木意味著在樹梢下方的森林中有一個陽光充足的區域，這使草可以進入並佔據。反過來，草改變了土壤溫度，使環境對某些其他型別的植被更加友好。以草為食的動物，包括駝鹿，麋鹿和一些鳥類，也從中受益。但是對於以白雲杉為生的生物來說，甲蟲的侵害是個壞訊息，例如鷹，貓頭鷹，紅松鼠和田鼠。軟體動物類的小型鼠類齧齒動物是生態系統中至關重要的部分，因為它們有助於傳播菌根真菌，附著在植物的根部並幫助它們吸收水分和養分。田鼠也是許多捕食者的重要食物。

生態系統變化總是傷害某些生物並幫助其他生物。因此，很難說變化總體上是好是壞。取而代之的是，生態學家（研究生態系統的人們）通常關注於對單個物種的影響：例如我們。在短期內，阿拉斯加雲杉甲蟲流行為許多人提供了柴火，但僅僅是摧毀了許多原本有價值的木材，並威脅了伐木工人的生計。而且沒有人能確定對森林的長期影響。在蟲害爆發，火災或重大風暴事件等干擾之後，生態系統趨於恢復到以前的狀態，但是如果阿拉斯加雲杉生態系統受到過多或過多幹擾，則可能會轉移到其他型別的森林，林地或森林中。草原代替。

在極端情況下，對生態系統的重大攻擊可能會導致徹底崩潰，從而使生態系統無法恢復原狀或過渡到新的健康狀態。結果是一個幾乎沒有生命的區域。在海洋中，生物學家將這些區域稱為死區。一個這樣的例子就是1990年代後期在印度洋發生的珊瑚礁死亡。

阿拉斯加和樹皮甲蟲

文章大意：

1。答題解析：答案：C；Subtle：微妙的。所以選C。

2。答題解析：答案：A；此段講氣候的影響講了兩點：（1）As the length of the warm season increased over the 1980s and 1990s， however， bark beetles had more time to fly from one tree to the next， burrow， and lay their eggs between the bark and the wood。有更長的時間在樹木之間來回穿梭併產卵。（2）The beetles had another thing going for them， too： a multi-year drought had weakened many of the spruce trees， leaving them vulnerable to attack。使更多的數容易被攻擊和理由，綜合兩點來看，deposit its eggs in a greater number of trees是可能實現的，A對。BCD均無支援。

3。答題解析：答案：A；第二段講了spruce bark beetle epidemic in Alaska發生的過程，第三段講了是the effects of the bark beetle epidemic，有好有壞，BUT之前講的好的，BUT之後講的壞的，D肯定不對，因為BUT之後為意思中心講的是壞處。A講後續events，即為the effects of the bark beetle epidemic意思

4。答題解析：答案：B；The grasses， in turn， changed the soil temperature， making the environment more friendly for some other types of vegetation。 Animals that feed on grasses， including moose， elk， and some birds， also benefited。顯然是B。

5。答題解析：答案是A和C；解析：Voles a type of small， mouselike rodent are an especially vital part of the ecosystem because they help spread mycorrhizal fungi， which attach to the roots of plants and help them take in water and nutrients。而現在Voles數量減少了，故C對D錯。Voles are also an important food for a number of predators。，現在Voles數量減少了，A對，B無體現。

6。答題解析：答案：B。轉折句，雖然ecosystem有恢復力，但是如果ALSKAN的生態系統被disturb太多，就可能恢復不了，而是變成另外一種生態系統。A只有“雖然”後的意思，沒有“但是”後所強調的重要資訊，C的Alaska might again become covered with woodlands or grasslands與原文“但是”後的資訊相反，D的資訊有錯，原文說的是Alaskan spruce ecosystem是否能恢復，並非討論一般的ecosystems。B的話是對原句的轉述。

7。答題解析：答案：A；講One such example is the coral reef die-off that happened in the Indian Ocean in the late 1990s。【其中一個例子就是上世紀90年代末發生在印度洋的珊瑚礁滅絕。】是為了印證前面的In extreme cases， major assaults on ecosystems can lead to a total collapse in which the ecosystem doesn’t bounce back to the way it was or transition to a new， healthy state。 The result is an area with very little life； in the oceans， biologists refer to these areas as dead zones。，【在極端情況下，對生態系統的重大攻擊可能導致生態系統的全面崩潰，無法恢復到原來的狀態或過渡到一個新的、健康的狀態。結果是一個幾乎沒有生命的區域；在海洋中，生物學家稱這些區域為死亡區。】顯然為A。D錯在affected by a nearby dead zone

8。答題解析：答案：D；

ABC均無法回答，而第四段的In the short term， the Alaskan spruce beetle epidemic supplied a lot of people with firewood， but only by destroying tons of otherwise valuable timber and threatening the livelihoods of loggers。 And no one knows for sure what the long-term impacts on the forest will be。【在短期內，阿拉斯加雲杉甲蟲的流行為人們提供了大量的柴火，但它摧毀了數噸原本很有價值的木材，並威脅到伐木工的生計。沒有人確切知道對森林的長期影響會是什麼。】長期effects不知，但一些短期effects，如有更多的木柴，所以D對，這裡說的是some of the effects，不一定要知道total effects。

9。答題解析：答案：C；

前文應該提到this limited perspective，根據語境知指對人類的effects，即只看對人類的影響不看對整個生態的影響。後面要具體闡述為什麼not completely straightforward。對應C，C前面說focus on the impacts on a single species： for instance， us。，C之後說短期可能有益，長期對人類影響未知，有壞有好，長短期effects不一樣，故顯得not completely straightforward。

10。答題解析：答案：A B C；

D錯在epidemic in mycorrhizal fungi，原文講的是Voles數量變少，影響到mycorrhizal fungi的擴散，並非造成了mycorrhizal fungi因傳染病而亡。E的話，第四段說Ecosystem changes always hurt some living creatures and help others。 It’s hard to say， therefore， whether a change is good or bad overall。。F的but after a transition period as a dead zone， they are able to return to their original state。沒有體現。A注意到第二段論點The biggest climate-caused ecosystem shifts today are happening at the world’s most northern latitudes， where the temperature over the last century has been rising about two times faster than the global average。B為第二段和第三段的概括，C為第四段和第五段的概括。

劉凱老師

解析：

劉凱，男，蒙古族，黑龍江省齊齊哈爾人。本科為哈爾濱師範大學英語系，碩士為北京理工大學。2010年赴美國賓夕法尼亞大學交流學習；2013年美國亞利桑那大學訪問學者；2015年澳大利亞新南威爾士大學ESL研修；2018年加州理工學院語言學雙學位獲得者；2019年赴澳大利亞麥考瑞大學交流習；GRE托福考試全球高分獲得者；榮獲長江商學院EMBA。

北京市優秀青年教師，北京市級重點高中示範校骨幹教師，多年高中一線執教經驗，高三年級把關教師，多次參與東城區模擬試題命題工作，教學理念先進，教學成果突出，多篇教學論文獲市區級獎項。多篇文章發表在《中國教育報》《中國考試》《北京教育》等報刊上。多次參加高考閱卷工作，參與人民教育出版社、北京教育出版社、外研社等各類高考教學用書的編寫工作，有豐富的備考經驗，國際核心期刊發表多篇論文。

教育部課題研究員，參與國家十二五課題計劃，並作出突出貢獻，參與初中、高中各年級區級試題的命制，多次承擔區級和市級研究課任務。北京市科技英語優秀指導教師，所帶學生在各級英語口語、作文競賽中多次獲獎；將紮實的英語基本功和嚴謹的學術思想作為教學的基礎，課堂上善於寓教於樂，資訊量大，內容豐富，使學生在和諧的課堂氣氛下欣賞英語、享受英語、掌握英語、運用英語。

2009-2012年期間，多次受邀在北京廣播電臺主持英語高考大綱解析及英語新課程改革節目，學術功底深厚，兼具偶像派與實力派特點，教風親切灑脫，詼諧幽默，思維開闊，屢有奇思妙想，善於引導學生學以致用，對高考動向把握極其準確，深受學生和家長歡迎。尤其擅長英語語法和單詞記憶法。

海外生活學習十年，社科人文類學科偏愛者；10年雅思教齡，知名教師培訓師；指導上萬考生快速衝刺雅思寫作、閱讀，平均分數7。5分；獨創“段落清空”、極簡化“針對檢索式”閱讀法等眾多高效技法；每年雅思考試均在10次以上；均分8+；真題回憶準確度97%以上；貼近西式思路和語言指導學生寫作；善於幫助學生突破學術寫作思維瓶頸。講授科目有長難句、翻譯、四六級考試、閱讀和寫作；在2014、2015、2017、2019四年考研中，接受其培訓的所有考生中有近萬名考生取得高分。帶給學生的不只是考分的提高，更多的是對英語領悟和感知的突破。純正的英音、獨到的見解、睿智的思維和輕鬆幽默的語言，為其贏得了廣大學生的認同和喜愛。

資深考研培訓講師；

英語四六級考試天團高階講師；

雅思閱讀、雅思寫作培訓主講名師；

六級考試閱卷組成員；

深諳命題規律和解題套路，對英語的學習規律和方法見解獨特。

劉凱老師

重複是記憶之母。

用聽，用看，用心去觸控每個單詞，你便會有好的記憶。

中國人要學好英語就要有一點點變態。

介紹

課堂從不需點名，卻無人缺席

呼籲國人學習英語的態度：

英語教師很幸運也有責任與學生一同叩響世界之門