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The calling or singing of frogs plays an important role in their reproduction—specifically, in helping individuals find and select mates. Sound has many advantages as a communication signal.When sounds are broadcast, the auditory 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 advantages 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 used 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 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 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 as 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 male’s age matters to the female because older frogs have successfully survived the environmental 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(subjectively: 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 information 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 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 rapid 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 (rhythm 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 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 females 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 frogs
EXCEPT:
A. They 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 frog’s needing to orient itself toward the direction of the signal.
2. The author provides information about "the visual modality" in order to
A. emphasize that visual information plays a significant part in frog breeding
B. explain why some frogs breed at night, while others breed during the day
C. indicate the resourcefulness with which frogs overcome obstacles in sound travel during the breeding process
D. argue that auditory signals have advantages over visual signals for frog reproduction
3. The word "potential" in the passage is closest in meaning to
A. occasional
B. possible
C. easy
D. hidden
4.The word "favorable” in the passage is closest in meaning to
A. well populated
B. distant
C. extensive
D. advantageous
5.According to paragraph 3，female frogs who listen to frog songs are trying to determine whether a future mate
A. can protect future offspring from predators
B. has an important social position within the male chorus
C. has reached an age that indicates the ability to survive environmental challenges
D. is young enough to be able to produce many offspring
6. It can be inferred from paragraph 3 that female frogs are seeking mates who
A. can inhabit a variety of breeding sites
B. can occupy habitats at a distance from those of younger male frogs
C. have protected previous mates from environmental hazards
D. are likely to pass on traits that strengthen their offspring's chances of survival
7. The word "ambiguous" in the passage is closest in meaning to
A. unexpected
B. unclear
C. important
D. unhelpful
8.The word "convey" in the passage is closest in meaning to
A. transmit
B. add to
C. amplify
D. correct
9.Paragraph 4 implies that young frogs may call from cold areas for which of the following reasons?
A. To indicate superior strength over older males
B. To appear more attractive to females by sounding older than actually are
C. To be able to spend less energy in producing their call
D. To compete against fewer males for a female’s attention
10.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 condition
B. To distinguish tree frogs from other species of frogs
C. To indicate that survival is more difficult for frogs than for other vertebrates
D. To emphasize how physical effort calling requires
11.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 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 reproduce
D. It makes it possible for frogs to invest more of their energy into producing eggs.
12.According to paragraph 6, tungara frogs add a chuck sound to their call in order to
A. make themselves more attractive to females
B. keep predators at a safe distance
C. attract frogs of different species
D. increase the loudness of their calls
13. Look at the four squares ■ that indicate where the following sentence could be added to the passage.
But a frog’s age is not the only influence on the pitch of a frog’s 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 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 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 rapid 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.
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 express 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, 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 obtain information from a male’s 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 young 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 the calling effort among many individuals.
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