How does an ecosystem （生態(tài)系統(tǒng)） work？What makes the populations of different species the way they are？Why are there so many flies and so few wolves？To find an answer，scientists have built mathematical models of food webs，noting who eats whom and how much each one eats.
With such models，scientists have found out some key principles operating in food webs.Most food webs，for instance，consist of many weak links rather than a few strong ones.When a predator （掠食動物） always eats huge numbers of a single prey （獵物） ，the two species are strongly linked；when a predator lives on various species，they are weakly linked.Food webs may be dominated by many weak links because that arrangement is more stable over the long term.If a predator can eat several species，it can survive the extinction （滅絕） of one of them.And if a predator can move on to another species that is easier to find when a prey species becomes rare，the switch allows the original prey to recover.The weak links may thus keep species from driving one another to extinction.
Mathematical models have also revealed that food webs may be unstable，where small changes of top predators can lead to big effects throughout entire ecosystems.In the 1960s，scientists proposed that predators at the top of a food web had a surprising amount of control over the size of populations of other species—including species they did not directly attack.
And unplanned human activities have proved the idea of top-down control by top predators to be true.In the ocean，we fished for top predators such as cod on an industrial scale，while on land，we killed off large predators such as wolves.These actions have greatly affected the ecological balance.
Scientists have built an early-warning system based on mathematical models.Ideally，the system would tell us when to adapt human activities that are pushing an ecosystem toward a breakdown or would even allow us to pull an ecosystem back from the borderline.Prevention is key，scientists say，because once ecosystems pass their tipping point （臨界點） ，it is remarkably difficult for them to return.
（1）A strong link is found between two species when a predator CC.
A．has a wide food choice
B．can easily find new prey
C．sticks to one prey species
D．can quickly move to another place
（2）What will happen if the populations of top predators in a food web greatly decline？ DD
A．The prey species they directly attack will die out.
B．The species they indirectly attack will turn into top predators.
C．The living environment of other species will remain unchanged.
D．The populations of other species will experience unexpected changes.
（3）What conclusion can be drawn from the examples in Paragraph 4？ AA
A．Uncontrolled human activities greatly upset ecosystems.
B．Rapid economic development threatens animal habitats.
C．Species of commercial value dominate other species.
D．Industrial activities help keep food webs stable.
（4）How does an early-warning system help us maintain the ecological balance？ DD
A．By getting illegal practices under control.
B．By stopping us from killing large predators.
C．By bringing the broken-down ecosystems back to normal.
D．By signaling the urgent need for taking preventive action.
【考點】說明文．
【答案】C；D；A；D
【解答】
【點評】
聲明：本試題解析著作權(quán)屬菁優(yōu)網(wǎng)所有，未經(jīng)書面同意，不得復(fù)制發(fā)布。
發(fā)布：2024/4/20 14:35:0組卷：10引用：3難度：0.5
相似題
-
1．It is widely believed that biodiversity（生物多樣性）is promoted to save species.But in reality species exist only as part of ecosystems and cannot survive unless their ecosystems are protected along with as much as possible of the diversity they contain.
Protecting habitats（棲息地）is important for keeping biodiversity.In 2003，over 102，000 habitats covering nearly 19 million square kilometres，or 11.5% of the world's land surface，were under some form of protection.Though this is a great improvement since 1962，when just 1，000 protected habitats were listed，it is still not considered enough to stop the ecocide that is endangering the world's biodiversity.
For a number of environmentalist，protecting the world's 25 biodiversity hotspots（熱點地區(qū)）is critical to saving habitats and species.But many hotspots are endangered already，having lost up to three-quarters of their original plants.
The poor state of most biodiversity hotspots results directly from population growth and migration（遷移） into these areas.A study found that by the mid-1990s around 1.1 billion people lived in these hotspots.Moreover，the annual population growth rate in these areas was 1.8%，higher than the global average of 1.4%.The PAI report concluded that human-related environmental changes will continue to put pressure on hotspots.Therefore，keeping biodiversity requires paying close attention to population size.
Protecting hotspots is not simply a matter of putting up fences and employing guards.The best results are achieved when local people are educated about the value of wildlife，and actually gain a share of the benefits from eco-tourism.Only then do they have a chance to see the benefits of protecting hotpots.
（1）What can we infer from paragraph 1？
A．The loss of any species can affect humans.
B．Endangered species are paid more attention to by humans.
C．Species can still survive when their ecosystems are destroyed.
D．Ecosystem protection is as important as diversity protection.
（2）What does the underlined word "ecocide" in paragraph 2 mean？
A．Ecosystem protection.
B．Reduction of the number of species.
C．Serious damage to habitats.
D．Habitats protection.
（3）What's the direct cause of the terrible state of the hotspots？
A．Population growth in hotpots.
B．Migration out of these areas.
C．Global warming.
D．The global average population growth rate.
（4）What's the author's opinion on protecting the hotspots？
A．It's simple to carry out.
B．It leads to the increase of tourists.
C．It's closely connected with local people.
D．It suggests that the local people are well educated.發(fā)布：2025/1/6 16:30:6組卷：0引用：1難度：0.5 -
2．Most of us spend our lives seeking the natural world.We go fishing，sit in the garden，have a picnic，live in the suburbs or go to the seaside.The most popular leisure activity in Britain is going for a walk.When joggers jog，they don't run on the streets.Every one of them tends to go to the park or the river.
But despite this，our children are growing up naturedeprived（剝奪）.I spent my boyhood climbing trees.These days，children are robbed of the ancient freedom，due to problems like crime，traffic，the loss of the open space and strange new ideas about what is best for children，that is to say，things that can be bought，rather than things that can be found.
The truth is to be found elsewhere.A study in the US：families had moved to better housing and the children were assessed for ADHD—Attention Deficit Hyperactivity Disorder（注意力缺陷多動癥）.Those whose accommodation had more natural views showed an improvement of 19%；those who had the same improvement in material surroundings but no nice view improved just 4%.
ADHD is one of the great problems of modern childhood.One study after another indicates that contact with nature gives huge benefits to ADHD children.However，we spend money on drugs rather than on green places.
The life of old people is measurably better when they have access to nature.The increasing concern for the growing population of old people is in quality rather than quantity of years.And study after study finds that a garden is the single most important thing in finding that quality.Even problems with crime and aggressive behaviour are reduced when there is contact with the natural world.
We need the wild world.It is essential to our wellbeing，our health and our happiness.
（1）According to the author，people enjoyto seek nature.
A．jogging on the street
B．running in the gym
C．shopping in the supermarket
D．sitting in the garden
（2）From the second paragraph，we can see that.
A．Children don't want to approach nature
B．children probably spend less time in nature nowadays
C．climbing trees will certainly do good to the children
D．children tend to be happier as a result of their material satisfaction
（3）In what way do people benefit from their contact with nature？
A．Children with ADHD can be cured.
B．Children's performance at school is greatly improved.
C．Problems with crime and violent behavior will easily be solved.
D．A garden nearby improves the quality of old people's life.
（4）what is the main idea of this passage？
A．Access to nature improves our life.
B．Nature treats children for ADHD.
C．Getting close to nature reduces crime.
D．Man can't live without natural areas.發(fā)布：2025/1/6 16:30:6組卷：0引用：1難度：0.5 -
3．New editions of Roald Dahl's classic books，such as Charlie and the Chocolate Factory and Matilda，are now available in bookstores.Some passages relating to weight，mental health，gender and race were changed.The changes made by Puffin Books，a division of Penguin Random House，first were reported by Britain's Daily Telegraph newspaper.
The changes to Dahl's books mark the latest debate over cultural sensitivity.Those who support updates seek to protect young people from cultural，ethnic and gender stereotypes in literature and other media.Critics complain that revisions to suit 21st century sensibilities risk weakening the genius of great artists and preventing readers from facing the world as it is.
The Roald Dahl Story Company controls the rights to the books.The company said it worked with Puffin Books to review the texts because it wanted to ensure that"Dahl's wonderful stories and characters continue to be enjoyed by all children today."
Inclusive Minds，a group that is working to make children's literature more inclusive and accessible，reviewed the language in a partnership effort with Puffin Books.Inclusive language avoids terms that could be seen as excluding specific groups of people.Any changes were"small and carefully considered，"the company said.
"When publishing new print runs of books written years ago，it's not unusual to review the language used alongside updating other details，including a book's cover and page layout，"the company said their guiding principle throughout had been to maintain the storylines，characters，and the spirit of the original text.
PEN America，a community of some 7，500 writers that advocates for freedom of expression，said it was"alarmed"by reports of the changes to Dahl's books.Suzanne Nossel，chief executive of PEN America，commented on Twitter.She said if we try"to correct for sensing slights （怠慢） instead of allowing readers to receive and react to books as written，we risk distorting the work of great authors and clouding the essential lens （透鏡） that literature offers on society."
Laura Hackett is a childhood Dahl fan who is now deputy literary editor of London，England's Sunday Times newspaper.She had a more personal reaction to the news."The editors at Puffin should be ashamed of the botched surgery they've carried out on some of the finest children's literature in Britain，"she wrote."As for me，I'll be carefully putting away my old，original copies of Dahl's stories，so that one day my children can enjoy them in their full，nasty and colorful glory."
（1）What is the reason for the changes to Dahl's books？
A．To make Dahl's books more enjoyable.
B．To review the language used and add details.
C．To remove words that show disrespect to some people.
D．To keep the storylines，characters，and the spirit of the original text.
（2）What might the underlined word in Paragraph 6 probably mean？
A．Preventing.
B．Appreciating.
C．Understanding.
D．Misrepresenting.
（3）Which of the following may Laura Hackett agree？
A．The new version of the books is worth collecting.
B．The original version of the books are more valuable.
C．The original books weaken the genius of great artists.
D．The new version allows readers to receive books as written.
（4）What might be the proper title of the passage？
A．New Changes to Roald Dahl Books Start Argument
B．Different Opinions on New Editions of Classic Books
C．Authors or Publishers both Control the Right to Books
D．New Editions of Roald Dahl's Classic Books Available
（5）What is the purpose of the passage？
A．To persuade readers to buy Roald Dahl's classic books.
B．To entertain readers by the changes of Roald Dahl's books.
C．To recommend the new version of Roald Dahl's classic books.
D．To inform diverse views on the changes of Roald DahI's books.發(fā)布：2025/1/30 8:0:1組卷：1引用：1難度：0.4
相關(guān)試卷