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1、 为了帮助大家高效备考托福, 为大家带来托福 TPO44 阅读 Passage3 原文文本+题目+答案 解析,希望对大家备考有所帮助。 Seagrasses Many areas of the shallow sea bottom are covered with a lush growth of aquatic flowering plants adapted to live submerged in seawater. A These plants are collectively called seagrasses.B Seagrass beds are strongly influen
2、ced by several physical factors.C The most significant is water motion:currents and waves.D Since seagrass systems exist in both sheltered and relatively open areas,they are subject to differing amounts of water motion.For any given seagrass system,however,the water motion is relatively constant.Sea
3、grass meadows in relatively turbulent waters tend to form a mosaic of individual mounds,whereas meadows in relatively calm waters tend to form flat,extensive carpets.The seagrass beds,in turn,dampen wave action,particularly if the blades reach the water surface.This damping effect can be significant
4、 to the point where just one meter into a seagrass bed the wave motion can be reduced to zero.Currents are also slowed as they move into the bed. The slowing of wave action and currents means that seagrass beds tend to accumulate sediment.However,this is not universal and depends on the currents und
5、er which the bed exists.Seagrass beds under the influence of strong currents tend to have many of the lighter particles,including seagrass debris,moved out,whereas beds in weak current areas accumulate lighter detrital material.It is interesting that temperate seagrass beds accumulate sediments from
6、 sources outside the beds,whereas tropical seagrass beds derive most of their sediments from within. Since most seagrass systems are depositional environments,they eventually accumulate organic material that leads to the creation of fine-grained sediments with a much higher organic content than that
7、 of the surrounding unvegetated areas.This accumulation,in turn,reduces the water movement and the oxygen supply.The high rate of metabolism(the processing of energy for survival)of the microorganisms in the sediments causes sediments to be anaerobic(without oxygen)below the first few millimeters.Ac
8、cording to ecologist J.W.Kenworthy,anaerobic processes of the microorganisms in the sediment are an important mechanism for regenerating and recycling nutrients and carbon,ensuring the high rates of productivitythat is,the amount of organic material producedthat are measured in those beds.In contras
9、t to other productivity in the ocean,which is confined to various species of algae and bacteria dependent on nutrient concentrations in the water column,seagrasses are rooted plants that absorb nutrients from the sediment or substrate.They are,therefore,capable of recycling nutrients into the ecosys
10、tem that would otherwise be trapped in the bottom and rendered unavailable. Other physical factors that have an effect on seagrass beds include light,temperature,and desiccation(drying out).For example,water depth and turbidity(density of particles in the water)together or separately control the amo
11、unt of light available to the plants and the depth to which the seagrasses may extend.Although marine botanist W.A.Setchell suggested early on that temperature was critical to the growth and reproduction of eelgrass,it has since been shown that this particularly widespread seagrass grows and reprodu
12、ces at temperatures between 2 and 4 degrees Celsius in the Arctic and at temperatures up to 28 degrees Celsius on the northeastern coast of the United States.Still,extreme temperatures,in combination with other factors,may have dramatic detrimental effects.For example,in areas of the cold North Atla
13、ntic,ice may form in winter.Researchers Robertson and Mann note that when the ice begins to break up,the wind and tides may move the ice around,scouring the bottom and uprooting the eelgrass.In contrast,at the southern end of the eelgrass range,on the southeastern coast of the United States,temperat
14、ures over 30 degrees Celsius in summer cause excessive mortality.Seagrass beds also decline if they are subjected to too much exposure to the air.The effect of desiccation is often difficult to separate from the effect of temperature.Most seagrass beds seem tolerant of considerable changes in salini
15、ty(salt levels)and can be found in brackish(somewhat salty)waters as well as in full-strength seawater. Paragraph 1 Many areas of the shallow sea bottom are covered with a lush growth of aquatic flowering plants adapted to live submerged in seawater. A These plants are collectively called seagrasses
16、.B Seagrass beds are strongly influenced by several physical factors.C The most significant is water motion:currents and waves.D Since seagrass systems exist in both sheltered and relatively open areas,they are subject to differing amounts of water motion.For any given seagrass system,however,the wa
17、ter motion is relatively constant.Seagrass meadows in relatively turbulent waters tend to form a mosaic of individual mounds,whereas meadows in relatively calm waters tend to form flat,extensive carpets.The seagrass beds,in turn,dampen wave action,particularly if the blades reach the water surface.T
18、his damping effect can be significant to the point where just one meter into a seagrass bed the wave motion can be reduced to zero.Currents are also slowed as they move into the bed. 1.According to paragraph 1,which of the following is true about seagrasses in calm ocean waters?A.They will not survi
19、ve for very long without the nutrients brought in by fast-moving waters. B.They tend to form beds covering large areas along the ocean floor. C.They usually are arranged in separate mounds. D.They grow more slowly than do seagrasses in fast-moving waters. 2.According to paragraph 1,which of the foll
20、owing is MOST likely to describe a bed in which seagrasses reach the surface of the water? A.The water is almost completely still. B.The bed often has major damage from strong waves or currents. C.The bed is generally no more than one square meter in size. D.Grasses form a mosaic of individual mound
21、s. Paragraph 2 The slowing of wave action and currents means that seagrass beds tend to accumulate sediment.However,this is not universal and depends on the currents under which the bed exists.Seagrass beds under the influence of strong currents tend to have many of the lighter particles,including s
22、eagrass debris,moved out,whereas beds in weak current areas accumulate lighter detrital material.It is interesting that temperate seagrass beds accumulate sediments from sources outside the beds,whereas tropical seagrass beds derive most of their sediments from within. 3.Which of the sentences below
23、 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.Light particles and debris collect in some seagrass beds,but are washed out of those affected by strong currents. B.Seagra
24、ss beds under the influence of strong currents tend to accumulate many of the lighter particles from other beds C.The strength of the currents determines how quickly accumulated seagrass debris is moved out of the beds. D.Seagrass debris and other light particles are often moved from areas of strong
25、 currents to areas of weak currents. 4.The word“derive”in paragraph 2 is closest in meaning to A.maintain B.expel C.obtain D.enrich Paragraph 3 Since most seagrass systems are depositional environments,they eventually accumulate organic material that leads to the creation of fine-grained sediments w
26、ith a much higher organic content than that of the surrounding unvegetated areas.This accumulation,in turn,reduces the water movement and the oxygen supply.The high rate of metabolism(the processing of energy for survival)of the microorganisms in the sediments causes sediments to be anaerobic(withou
27、t oxygen)below the first few millimeters.According to ecologist J.W.Kenworthy,anaerobic processes of the microorganisms in the sediment are an important mechanism for regenerating and recycling nutrients and carbon,ensuring the high rates of productivitythat is,the amount of organic material produce
28、dthat are measured in those beds.In contrast to other productivity in the ocean,which is confined to various species of algae and bacteria dependent on nutrient concentrations in the water column,seagrasses are rooted plants that absorb nutrients from the sediment or substrate.They are,therefore,cap
29、able of recycling nutrients into the ecosystem that would otherwise be trapped in the bottom and rendered unavailable. 5.According to paragraph 3,which of the following does NOT accurately describe the sediments that collect in seagrass beds? A.Fine-grained B.Only a few millimeters deep C.Low in oxy
30、gen D.Rich in organic matter 6.The word“confined”in paragraph 3 is closest in meaning to A.related B.limited C.relevant D.helpful 7.According to paragraph 3,how do seagrasses affect the nutrient supply in the ecosystem? A.Because of their high rate of metabolism,they consume a large percentage of th
31、e available nutrients. B.They attract various species of algae and bacteria that produce high nutrient concentrations in the water column. C.They take up carbon and other nutrients trapped on the sea bottom and bring them back into use. D.Through anaerobic processes at their roots,they produce a ver
32、y nutrient-rich sediment. Paragraph 4 Other physical factors that have an effect on seagrass beds include light,temperature,and desiccation(drying out).For example,water depth and turbidity(density of particles in the water)together or separately control the amount of light available to the plants a
33、nd the depth to which the seagrasses may extend.Although marine botanist W.A.Setchell suggested early on that temperature was critical to the growth and reproduction of eelgrass,it has since been shown that this particularly widespread seagrass grows and reproduces at temperatures between 2 and 4 de
34、grees Celsius in the Arctic and at temperatures up to 28 degrees Celsius on the northeastern coast of the United States.Still,extreme temperatures,in combination with other factors,may have dramatic detrimental effects.For example,in areas of the cold North Atlantic,ice may form in winter.Researcher
35、s Robertson and Mann note that when the ice begins to break up,the wind and tides may move the ice around,scouring the bottom and uprooting the eelgrass.In contrast,at the southern end of the eelgrass range,on the southeastern coast of the United States,temperatures over 30 degrees Celsius in summer
36、 cause excessive mortality.Seagrass beds also decline if they are subjected to too much exposure to the air.The effect of desiccation is often difficult to separate from the effect of temperature.Most seagrass beds seem tolerant of considerable changes in salinity(salt levels)and can be found in bra
37、ckish(somewhat salty)waters as well as in full-strength seawater. 8.It can be inferred from paragraph 4 that the reason seagrasses do not grow in very deep water is that A.They cannot handle intense water pressure. B.Deep water is too cold. C.They would not get enough light. D.Deep water is too salt
38、y. 9.In paragraph 4,why does the author mention that eelgrass thrives in both the Arctic and in the northeastern United States? A.To show that environments with extreme temperatures rarely have any effect on eelgrass B.To identify the northern and southern limits of the range where eelgrass is found
39、 C.To support the authors statement that eelgrass is a particularly widespread kind of seagrass D.To cite evidence tending to disprove one view about the importance of temperature to the growth of eelgrass 10.The word“detrimental”in paragraph 4 is closest in meaning to A.Harmful B.Significant C.Unex
40、pected D.Distinct 11.Paragraph 4 suggests that which of the following would be the LEAST likely to cause major damage to eelgrass and other common seagrasses? A.Factors related to extreme temperatures B.Exposure to air C.Major changes in salinity D.The movement of ice on the seafloor 12.The phrase“t
41、olerant of”in paragraph 4 is closest in meaning to A.unused to B.strongly affected by C.protected from D.able to withstand 13.Look at the four squaresthat indicate where the following sentence could be added to the passage. Seagrasses grow together in dense patches,or beds,with as many as 4,000 blad
42、es per square meter. Where would the sentence best fit?Click on a squareto add the sentence to the passage 14.Look at the four squaresthat indicate where the following sentence could be added to the passage. Seagrasses grow together in dense patches,or beds,with as many as 4,000 blades per square me
43、ter. Where would the sentence best fit?Click on a squareto add the sentence to the passage Drag your answer choices to the spaces where they belong.To remove an answer choice,click on it. To review the passage,click VIEW TEXT Seagrasses are aquatic flowering plants that grow in either sheltered or o
44、pen areas of the sea. A.Seagrass beds are influenced by several physical factors,the most significant being the stability of the sea bottom,which must anchor them against the currents. B.Because the slow currents and waves,seagrass beds collect deposits of rich organic sediments,which are home to ma
45、ny anaerobic microorganisms. C.Unlike sea organisms that depend on the water column for their productivity,seagrasses ensure high rates of productivity by taking nutrients from ocean floor sediment. D.Sediments in seagrass beds vary by region,with temperate beds accumulating sediments from within,an
46、d tropical beds collecting sediments from without. E.Seagrasses under weak currents tend to have higher rates of metabolism than those under strong currents,perhaps because of differences in oxygen levels. F.Although seagrasses survive in temperatures ranging from 2 to 28 degrees Celsius,more extrem
47、e temperatures can damage them,as can desiccation and lack of light. Q1 正确答案:B 解析:第一段介绍,水的动静状态会影响 seagrasses,在相对静止的水体中:“meadows in relatively calm waters tend to form flat,extensive carpets” ,也就是形成又宽又 平的 seagrasses beds。B 选项正确。 Q2 正确答案:A 解析:回归答案定位句“This damping effect can be significant towave motio
48、n can be reduced to zero.”本段后三句说明 seagrass beds 有减弱水流流动的作用,所以如果 seagrasses 生长非常旺盛、以至于抵达水面附近,那么对水流的减缓作用非常大:甚至达到 静止(zero)。A 选项正确。 Q3 正确答案:A 解析:分析一下句子结构:在 strong currents 的影响下,seagrass beds 会有很多 lighter particles 被移出(证明原来就是积累有这种物质的),whereas,但是,week currents beds 却积累了 lighter detrital material(轻碎屑物质)A 选
49、项转述正确。 Q4 正确答案:C 解析:本词所在句的意思是:很有意思的是,温带地区的 seagrass beds 积累沉淀物从 河床外来, 然而热带 seagrass beds 的沉积物大部分从河床本身得到。 这里的 “derive” 是 “得 到” “获取”的意思,C 项意义相符。其余选项分别是“维持” , “放逐” “使充实、富足”的 意思,不选。根据前后文,whereas 表示对比,derive 应该和前半句的 accumulatefrom 意 思相同,对比选项,也只能选 C。 Q5 正确答案:B 解析:其余关于沉积物的描述分别对应第三段开头的“fine-grained sediments” “reduces the water movement and the oxygen supply”以及“accumulate organic material” ,只有 B 选项没有提到。 Q6 正确答案:B 解析:本词所在句的意思是:海洋中其他生产有机物的过程只限于一些种类的 algae 和 细菌等。这里的“be confined to”短语意为“仅限于” ,与 B 选项的含义相符。其余选项分 别代表“有关系的,有关联的” , “相关的” “有用的,有帮助的” ,均不符合语境。 Q7 正确答案:C 解析:根据题干定位原文:“se
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