托福TPO阅读49原文(19页).doc

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1、-托福TPO阅读49原文-第 19 页托福TPO阅读49原文+题目+答案托福TPO阅读49原文（第一篇）-Mating Songs of FrogsThe calling or singing of frogs plays an important role in their reproductionspecifically, in helping individuals find and select mates. Sound has many advantages as a communication signal.When sounds are broadcast, the audito

2、ry receptors do not need to be in a particular orientation relative to the sound source in order to receive stimulation. Loud songs, particularly those made by choruses of frogs calling together, can travel long distances and thus attract distant frogs.Sounds travel around large obstacles. These adv

3、antages are not found in the visual modality,where the receiver must be attentive and have its visual receptor orientated in the correct direction.Further, most frogs and toads breed at night, when light levels are low but sounds can be easily localized. We can conclude that auditory signals are use

4、d by frogs and toads because they can be effective over long distances at night.Male frogs do most of the courtship calling. Other male frogs can respond by adding their voices to form a calling chorus. Male frogs can also vocalize to each other as part of aggressive displays.Aggressive calls can be

5、 distinct from the advertisement calls used to attract females. Females can respond to male songs by moving toward the sound source or by selecting certain males as reproductive partners. In some species females also respond to males by calling: receptive pairs can even perform duets. Predators may

6、also cue in on calling frogs as potential prey.Frog songs contain several potentially important pieces of information about the calling male.First, sound amplitude can indicate the size of the individual that is Galling. Since many frogs exhibit indeterminate growth (i.e., they keep getting bigger a

7、s they get older), size is a good predictor of relative age. In many species, call amplitude is increased by specialized vocal sacs that can enlarge as the animal grows; thus, older frogs produce louder calls. The males age matters to the female because older frogs have successfully survived the env

8、ironmental hazards that the offspring they sire will soon be facing. Amplitude can also convey information on how far away the calling frog is or, for choruses, how many frogs are calling together. An intensely vocalizing chorus may indicate a particularly favorable breeding site. Sound amplitude(su

9、bjectively: loudness) can be an ambiguous cue for a female, however. A very intense sound can indicate an old male at some distance or a younger male that is close. A close, small chorus could be confused with a louder chorus that is farther away.Sound frequencies-or pitch-can also convey informatio

10、n about the calling male because the vocal apparatus grows larger as the frog grows older. In some frogs, the pitch of individual sounds varies with so that older and larger males give lower-pitched calls. Sound pitch is affected by temperature; small males can mimic the lower pitch of larger, older

11、 males by calling from colder locations. Finally, the length of time that an individual can afford to spend calling is a good indicator of his health. Many frogs invest considerable energy in calling, both because they do not feed and because it is a physically demanding behavior that relies on rapi

12、d muscular contractions of the vocalization apparatus. This effort can be debilitating in a male frog that is not in top physical condition. Calling in tree frogs is said to be the most energetically expensive behavior yet measured any vertebrate.Sound frequencies and the overall temporal pattern (r

13、hythm and rate) of the song can also reveal the species of the calling male. The frequencies sounds and their temporal patterns are speciesspecific.The species of a potential mate is extremely important to the female. Females that choose to mate with members of another species risk losing the energy

14、 invest in eggs because the hybrid offspring will not survive and reproduce.Thu complexity of a frog song can also affect how attractive it is to a female. The songs of male tungara frogs, for example, can consist simply of short high-frequency “whines” or by several lower-frequency chucks. More fem

15、ales approach loudspeakers playing whines plus chucks than whines alone. The addition of chucks, however, also has the disadvantage of attracting bats that eat the frogs. 托福TPO阅读49原文+题目：1. According to paragraph 1, all of the following are mentioned as true of the mating calls of frogsEXCEPT:A. They

16、 can reach frogs in far-off locations.B. They are not blocked by objects of substantial size.C. They are often combined with non-auditory signals.D. They err be received without the frogs needing to orient itself toward the direction of the signal.2. The author provides information about the visual

17、modality in order toA. emphasize that visual information plays a significant part in frog breedingB. explain why some frogs breed at night, while others breed during the dayC. indicate the resourcefulness with which frogs overcome obstacles in sound travel during the breeding processD. argue that au

18、ditory signals have advantages over visual signals for frog reproduction3. The word potential in the passage is closest in meaning toA. occasionalB. possibleC. easyD. hidden4.The word favorable” in the passage is closest in meaning toA. well populatedB. distantC. extensiveD. advantageous5.According

19、to paragraph 3，female frogs who listen to frog songs are trying to determine whether a future mateA. can protect future offspring from predatorsB. has an important social position within the male chorusC. has reached an age that indicates the ability to survive environmental challengesD. is young en

20、ough to be able to produce many offspring6. It can be inferred from paragraph 3 that female frogs are seeking mates whoA. can inhabit a variety of breeding sitesB. can occupy habitats at a distance from those of younger male frogsC. have protected previous mates from environmental hazardsD. are like

21、ly to pass on traits that strengthen their offsprings chances of survival7. The word ambiguous in the passage is closest in meaning toA. unexpectedB. unclearC. importantD. unhelpful8.The word convey in the passage is closest in meaning toA. transmitB. add toC. amplifyD. correct9.Paragraph 4 implies

22、that young frogs may call from cold areas for which of the following reasons?A. To indicate superior strength over older malesB. To appear more attractive to females by sounding older than actually areC. To be able to spend less energy in producing their callD. To compete against fewer males for a f

23、emales attention10.In paragraph 4, why does the author mention that tree frog calling is said to be “the most energetically expensive behavior yet measured in any vertebrate?A. explain why it is important for tree frogs to be in top physical conditionB. To distinguish tree frogs from other species o

24、f frogsC. To indicate that survival is more difficult for frogs than for other vertebratesD. To emphasize how physical effort calling requires11.It can be inferred paragraph 5 that having species specific songs benefits frogs in which of the following ways?A. It enables frogs to better protect eggs

25、from being damaged by members of other species.B. It make it possible for frogs to judge their distance from potential mates.C. It helps frogs to avoid having offspring that cannot survive and reproduceD. It makes it possible for frogs to invest more of their energy into producing eggs.12.According

26、to paragraph 6, tungara frogs add a chuck sound to their call in order toA. make themselves more attractive to femalesB. keep predators at a safe distanceC. attract frogs of different speciesD. increase the loudness of their calls13. Look at the four squares that indicate where the following sentenc

27、e could be added to the passage.But a frogs age is not the only influence on the pitch of a frogs call.Where would the sentence best fit? Sound frequencies-or pitch-can also convey information about the calling male because the vocal apparatus grows larger as the frog grows older. In some frogs, the

28、 pitch of individual sounds varies with so that older and larger males give lower-pitched calls. Sound pitch if affected by temperature; small males can mimic the lower pitch of larger, older males by calling from colder locations. Finally, the length of time that an individual can afford to spend c

29、alling is a good indicator of his health. Many frogs invest considerable energy in calling, both because they do not feed and because it is a physically demanding behavior that relies on rapid muscular contractions of the vocalization apparatus. This effort can be debilitating in a male frog that is

30、 not in top physical condition. Calling in tree frogs is said to be the most energetically expensive behavior yet measured any vertebrate.14.Directions: An introductory sentence for a brief summary of the passage is provided below.Complete the summary by selecting the THREE answer choices that expre

31、ss the most important ideas in the passage. Some sentences 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 question is worth 2 points.The calling or singing of frogs is a form of communication.1.For frogs and toads

32、, sound has a number of advantages over visual signals as a medium of communication over long distances at night.2.Calling is performed primarily by male frogs to attract mates for reproduction and to actively compete with other male frogs for females.3.Depending on the species, female frogs can obt

33、ain information from a males song about age,health, and species of the caller.4.In some species both males and females produce mating songs either as individual pairs or as choruses, though the choruses are likely to attract predators;5.Frog calls are difficult to interpret because old frogs and you

34、ng frogs in cool places produce the same song, and near frogs that are old and weak can sound like fit young frogs calling from a distance.6.Because calling is such a tiring activity for frogs, it is used to communicate only about biologically necessary activities and often in groups that distribute

35、 the calling effort among many individuals.托福TPO阅读49原文（第二篇）-Human Impacts on BiogeographyBiologists, who commonly study the distribution of plant and animal species in different environmentstheir biogeographystrive to develop interpretations or explanations of the patterns of species distribution, b

36、ut these may be incorrect if the effects of human beings are not taken into consideration. In some cases, these effects may be accidental; for example, some species of rat were unintentionally transported aboard ships from Europe to the islands of the South Pacific. In other cases, species distribut

37、ions may have been deliberately modified by human beings. The Polynesians in the South Pacific intentionally moved the kumara (sweet potato) to islands in that region to provide the population with a new food crop.The relocation of species by humans (and more recently the imposition of restrictions

38、on movement by way of national controls and world conventions) has been primarily for economic reasons and for environmental protection. For example, humans introduced Sitka spruce trees into Scotland and England from North America to use them as a timber crop. Similarly the Monterey pine tree was i

39、ntroduced into New Zealand in the nineteenth century from California and has become the most widely used species in the timber production industry in that country. The potato has been carried from its native home in the high Andes of South America, modified and developed into many varieties, and tra

40、nsported around the world because it can be used as a food crop. The plant formerly known as the Chinese gooseberry was relocated from its native China to New Zealand where an industry was established around the renamed kiwifruit.We have extended the distribution of some species because of certain u

41、seful traits that make the species desirable beyond their former known range For example, willows have extensive root systems, can grow relatively quickly, and are now used in several countries worldwide to stabilize river margins as a flood protection measure. The distribution of willows has theref

42、ore been influenced considerably by human use in river bank management.The effects of introduced species can be many and varied and can include effects on the distribution of other species. For example, the North American gray squirrel was introduced into England and has now largely displaced the na

43、tive red squirrel. The accidental introduction of organisms to new areas may have major pest implications. The South African bronze butterfly, the larva (immature insect forms) of which feed on buds and other parts of geraniums and similar flowers, was accidentally introduced into the Balearic Islan

44、ds via imported geraniums. In its native South Africa, the distribution and abundance of the butterfly are affected in part by a native wasp that parasitizes (feeds on) the larvae. In the absence of the parasite wasp on the Balearic Islands off the coast of Spain, the butterfly has now spread to mai

45、nland Spain where its rapid spread has been accentuated by trade in garden plants and modem transport. The species has become a major pest due to the lack of a natural predator and is now causing great problems for the horticultural industry in Spain.Human-driven changes in the distribution of some

46、species may result in hybridization (interbreeding) with other species and so have a genetic effect. For example, the North American cord grass was accidentally introduced to the south coast of England in the early nineteenthcentury. It hybridized with the European cord grass and resulted in the pro

47、duction of a new species,which in this case is also a major pest plant of estuaries in England where it became dominant and extensive Information about a species distribution (prior to human modification) maybe applied in pest control programs for the introduced species. Studies of the species in it

48、s native habitat may yield information about the factors that limit or influence its distribution and population dynamics. That information may then be applied in the development of strategies to contain and control the spread of pest species. For example, information about the role of the parasitic wasp in the ecology of the bronze butterfly may be utilized in the process of finding control strategies for that species on mainland Spain.