1、A. The seriousness of big-tree loss in California.B. The increasing variety of California big trees.C. The distribution of big trees in California forests.D. The influence of farming on big trees in California.28. Which of the following is well-intentioned but may be bad for big trees?A. Ecological
2、studies of forests.B. Banning woodcutting.C. Limiting housing development.D. Fire control measures.29. What is a major cause of the water shortage according to Mclntyre?A. Inadequate snowmelt. B. A longer dry season.C. A warmer climate. D. Dampness of the air.30. What can be a suitable title for the
3、 text?A. Californias Forests: Where Have All the Big Trees Gone?B. Cutting of Big Trees to Be Prohibited in California SoonC. Why Are the Big Trees Important to California Forests?D. Patrick Mclntyre: Grow More Big Trees in California【答案】27. A 28. D 29. C 30. A【解析】文章主要讲述了美国加利福尼亚州的森林面临着的巨大危机,大型树木在急剧减
4、少,作者阐述了现象,并分析了其原因。27. A段落主旨题。根据文章第二段第三句The number of treesdeclined by 50 percentmore than 55 percent75 percent等数字可知,该段主要讲述了加州森林中大树急剧减少的严重性,故选A项。28. D推理判断题。根据第三段第三句Aggressive wildfire controlcompete with resources可知,由于激进的森林防火措施,虽然一定程度上保护了森林,但同时也导致小树泛滥,与大树争抢资源,从而导致大树数量骤减,所以选D项。29. C细节理解题。根据最后一段Since t
5、he 1930s, McIntyre saidhave been rising temperaturesreduces the water可知,水资源短缺的一个主因是逐渐上升的气候温度,故选C项。30. A主旨大意题。根据全文可知,主要讲述了美国加州森林中大树数量急剧下降的现象,并分析了原因。由此A项能很好地概括全文。2.D【2019北京】By the end of the century,if not sooner,the worlds oceans will be bluer and greener thanks to a warming climate,according to a ne
6、w study.At the heart of the phenomenon lie tiny marine microorganisms(海洋微生物)called phytoplankton. Because of the way light reflects off the organisms,these phytoplankton create colourful patterns at the ocean surface. Ocean colour varies from green to blue,depending on the type and concentration of
7、phytoplankton. Climate change will fuel the growth of phytoplankton in some areas,while reducing it in other spots,leading to changes in the oceans appearance.Phytoplankton live at the ocean surface,where they pull carbon dioxide(二氧化碳)into the ocean while giving off oxygen. When these organisms die,
8、they bury carbon in the deep ocean,an important process that helps to regulate the global climate. But phytoplankton are vulnerable to the oceans warming trend. Warming changes key characteristics of the ocean and can affect phytoplankton growth,since they need not only sunlight and carbon dioxide t
9、o grow,but also nutrients.Stephanie Dutkiewicz,a scientist in MITs Center for Global Change Science,built a climate model that projects changes to the oceans throughout the century. In a world that warms up by 3,it found that multiple changes to the colour of the oceans would occur. The model projec
10、ts that currently blue areas with little phytoplankton could become even bluer. But in some waters,such as those of the Arctic,a warming will make conditions riper for phytoplankton,and these areas will turn greener. “Not only are the quantities of phytoplankton in the ocean changing. ”she said,“but
11、 the type of phytoplankton is changing. ”42. What are the first two paragraphs mainly about?A. The various patterns at the ocean surface.B. The cause of the changes in ocean colour.C. The way light reflects off marine organisms.D. The efforts to fuel the growth of phytoplankton.43. What does the und
12、erlined word“vulnerable”in Paragraph 3 probably mean?A. Sensitive. B. Beneficial C. Significant D. Unnoticeable44. What can we learn from the passage?A. Phytoplankton play a declining role in the marine ecosystem.B. Dutkiewiczs model aims to project phytoplankton changesC. Phytoplankton have been us
13、ed to control global climateD. Oceans with more phytoplankton may appear greener.45. What is the main purpose of the passage?A. To assess the consequences of ocean colour changesB. To analyse the composition of the ocean food chainC. To explain the effects of climate change on oceansD. To introduce
14、a new method to study phytoplankton【答案】42. B 43. A 44. D 45. C【解析】本文是一篇科普知识类文章。主要介绍了由于气候变暖导致海洋微生物发生变化,进而导致海洋颜色的变化。42. B 主旨大意题。第一段的主要讲的是:根据一项新的研究,由于气候变暖,到本世纪末界上的海洋将会更蓝更绿;第二段主要介绍了海洋的颜色取决于浮游植物的种类和浓度。因为气候变化将促进某些地区浮游植物的生长,同时也会减少其他地区浮游植物的数量,从而导致海洋外观的变化。因此文章前两段的主要讲的是“海洋颜色变化的原因”。故选B。43. A 猜测词义题。根据第三段最后一句可知:
15、气候变暖会改变海洋的主要特征,并会影响浮游植物的生长,因为它们不仅需要阳光和二氧化碳来生长,还需要营养物质。因此,此处的“vulnerable”是“易受影响的”意思,即sensitive。significant重大的,有意义的;beneficial有益的;unnoticeable不明显的。故选A。44. D 推理判断题。从文章第四段中的“The model projects that currently blue areas with little phytoplankton could become even bluer. But in some waters, such as those
16、of the Arctic, a warming will make conditions riper for phytoplankton, and these areas will turn greener.”可知,“有更多浮游植物的海洋看起来更绿。”故选D。45. C 主旨大意题。根据整篇文章的内容来看,主要解释气候变化会导致海洋颜色的改变,而这种改变主要是因为浮游植物数量的变化,因此本文的主要目的是“解释气候变化对海洋的影响”。故选C。3.C【2019天津】How does an ecosystem(生态系统)work?What makes the populations of diff
17、erent 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,
18、for instance,consist of many weak links rather than a few strong ones. When a predator(掠食动物)always eats huge numbers of a single prey(猎物),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 ar
19、rangement is more stable over the long term. If a predator can eat several species,it can survive the extinction(灭绝)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
20、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
21、 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,
22、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 br
23、eakdown or would even allow us to pull an ecosystem back from the borderline. Prevention is key,scientists says because once ecosystems pass their tipping point(临界点),it is remarkably difficult for them to return.46. What have scientists discovered with the help of mathematical models of food webs?A.
24、 The living habits of species in food webs.B. The rules governing food webs of the ecosystems.C. The approaches to studying the species in the ecosystems.D. The differences between weak and strong links in food webs.47. A strong link is found between two species when a predator_A. has a wide food ch
25、oiceB. can easily find new preyC. sticks to one prey speciesD. can quickly move to another place48. What will happen if the populations of top predators in a food web greatly decline?A. The prey species they directly attack will die out.B. The species they indirectly attack will turn into top predat
26、ors.C. The living environment of other species will remain unchanged.D. The populations of other species will experience unexpected changes.49. What conclusion can be drawn from the examples in Paragraph 4?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 he
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