今天小编为大家整理的是关于2019年3月31日
How Birds Acquire Their Songs
Most songbirds hatch in the spring and then merely listen to the songs of adult male birds until sometime in late summer or autumn, when the adults stop singing, not to resume until the end of winter the following year. It is usually male birds that are doing the singing in northern latitudes, though female singing is common in the tropics. Many young songbirds do no singing of their own until nearly a year after their birth. With the coming of their second spring, their testosterone levels rise and this in turn prompts them to begin singing, with their song development following a predictable pattern over a period of weeks. At first, their songs may be a quiet, jumbled series of chirps and whistles. Over time, young birds begin to use the syllables of their species' songs, though the order in which these syllables appear will vary. Finally, their songs crystallize (take form) into the clear, orderly song of their species.
There is a songbird, called the white-crowned sparrow, whose song development follows this general script while providing some variations that are instructive about the interplay of internal influences and learning in birdsong. White-crowned sparrows raised in captivity will follow the pattern of song acquisition just described: they listen to songs in their first spring and summer but do not themselves begin singing until they are perhaps six months old. In nature, however, things are different. For example, the white-crown found year-round in the San Francisco area sings a particular regional variant or dialect of the basic white-crown song and begins singing within six weeks or so of birth and may progress to fully crystallized song as early as three months after birth, meaning about September.
Why would there be a difference between singing in nature and singing in the laboratory? The pressures of nature. ■ As year-round residents, the San Francisco white-crowns do not fly into an area in spring and then establish territories. ■ Rather, they establish territories as early as their first autumn. ■ One function of birdsong is to announce, I have a territory here. ■ Young white-crowns, like many species, will extend this practice by countersinging, meaning a male, upon hearing the song of a nearby male of its species, will repeat the exact song he has heard, thus setting off a back-and-forth duel, like two children in an argument, each of them saying, I'm still here.
Internal influences and learning are also on display in white-crowns in the way they acquire their songs.We know that there is often a so-called sensitive period for animal learning a kind of window in which an animal is able to acquire certain skills or information. In laboratory-raised white-crowns, the sensitive period starts at about ten days after birth and extends until about fifty days after birth. A white-crown that became deaf prior to the opening of the sensitive period eventually will sing individual notes, but it will never learn to sing its species' song. Meanwhile, white-crowns that are raised in nature through part of their sensitive period and then taken to the laboratory will begin singing the following winter in the dialect of the area in which they were hatched. Two points are worth observing about this. First, note that these birds are learning the white-crown song months before they ever start practicing it themselves. Indeed, the learning window will be closed completely (in their first summer) before these lab-reared birds ever sing a note (the following winter). Second, learning is important enough in song acquisition that white-crowns learn not just their species' song but local or regional variants of it, which they are able to recall months after last hearing them.
But what about internal influences? Interestingly, all white-crowns that are reared in isolation from birth eventually sing nearly identical versions of a kind of standard white-crown song. In other words, there seems to be a built-in version of the white-crown song that becomes modified with local dialects only when birds are raised in the wild. Beyond this, isolated white-crowns that are exposed to tapes of other species' songs will ignore the other birds' songs entirely and go on to sing the basic white-crown song. White-crowns are thus genetically disposed to learn their own song while ignoring the songs of others.
1. The word “prompts” in the passage is closest in meaning to
A. stimulates
B. strengthens
C. prepares
D. forces
2. According to paragraph 1, which of the following is true of male songbirds in the first year of life
A. They do not begin singing until sometime in late summer or autumn.
B. They begin singing earlier in the tropics than in northern latitudes.
C. They listen to songs of adults for an extended period of time before they themselves sing.
D. Their earliest songs contain the characteristic order of syllables for their species.
3. The word “particular” in the passage is closest in meaning to
A. popular
B. specific
C. well-known
D. complex
4. According to paragraphs 2 and 3, all of the following are true about San Francisco white-crowns EXCEPT:
A. They do not migrate to another area in spring to establish territories.
B. They completely acquire their song as early as three months after birth.
C. They establish territories in their first autumn.
D. They begin singing much earlier in captivity than they do in nature.
5. In paragraph 3, the author points out that San Francisco white-crowns establish their territories in the area in which they are born in order to explain which of the following
A. Why they practice counter-singing
B. Why they get better territories than white-crowns that establish territories in areas in which they are not born
C. Why they are more competitive than white-crowns raised in captivity
D. Why in their natural habitat they start singing earlier than white-crowns raised in captivity
6. Which of the sentences below 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. Many species, including white-crowns, use a dueling technique to spread the practice of countersinging to other males of the species.
B. A young white-crown male uses countersinging to learn the songs of nearby males by repeatedly practicing them.
C. A young white-crown male engages in countersinging with a nearby male in order to assert its continuing presence in its territory.
D. Young white-crown males, much like young children, are competitive.
7. The word “eventually” in the passage is closest in meaning to
A. generally
B. probably
C. in the end
D. at the least
8. The word “recall” in the passage is closest in meaning to
A. repeat
B. remember
C. recognize
D. complete
9. According to paragraph 4, white-crowns with which of the following life histories demonstrate the importance of memory in song acquisition
A. White-crowns that learn a dialect before they learn their standard song
B. White-crowns that first heard a dialect of the white-crown song before they were ten days old
C. White-crowns that were moved from where they were born to a different region during their sensitive period
D. White-crowns that were raised in nature through part of their sensitive period and then transferred to the laboratory
10. What can be inferred from paragraph 4 about the local dialect of the species song that a white-crown sings after the sensitive period has closed
A. Those dialects must be learned during the sensitive period and are retained thereafter even in new environments.
B. Those dialects can be learned after the sensitive period if they are common in the local area.
C. Those dialects can be learned after the sensitive period if the birds are raised in the laboratory.
D. Those dialects are learned during the sensitive period and afterward used only when they hear others sing them.
11. According to paragraph 5, which of the following statements is true about white-crowns reared in isolation that are exposed to tapes of other species' songs
A. The tapes cause the white-crowns to begin singing earlier than those not exposed to the tapes.
B. The tapes do not affect the white-crowns' singing development or change their song.
C. The tapes help the white-crowns learn the standard song of their species.
D. The tapes aid the white-crowns in learning local dialects of other species.
12. What can be inferred from paragraph 5 about the song of white-crowns raised in the wild
A. It is less complex than the song of birds raised in isolation.
B. It is the standard song of the white-crown species.
C. It is a mixture of the basic white-crown song and the dialects of other white-crowns that inhabit the local area.
D. It is identical to dialects learned from exposure to tapes.
13. Look at the four squares that indicate where the following sentence could be added to the passage.
So San Francisco white-crowns need to start quickly making their presence known.
Where would the sentence best fit? Click on a square to add the sentence to the passage.
14. Drag your choices to the spaces where they belong. To review the passage, click on View Text. Answer Choices
A. Male birds have a standard process for acquiring their songs that involves a sensitive period when learning takes place.
B. Birds raised in the wild can differ from those raised in captivity in when they begin to sing their song, which is used to establish their territory.
C. Testosterone levels in male birds affect the quality of the young bird's song.
D. Birds that do not need to establish their territory, such as those raised in isolation, are unlikely to learn to sing.
E. The learning of local dialects demonstrates that song acquisition involves both internal and environmental influences.
F. Birds raised in the wild may acquire the songs of other species in their local area.
参考答案
Q1A Q2C Q3B Q4D Q5D Q6B Q7A Q8B Q9D Q10A
Q11B Q12B Q13C Q14 ABE
以上就是小编整理的精彩内容2019年3月31日托福阅读机经大范围预测一文，希望大家托福阅读考取理想成绩!