托福阅读tpo69R-1原文+译文+题目+答案+背景知识

TPO69阅读-1Why Snakes Have Forked Tongues
原文 (1)
译文 (3)
题目 (4)
答案 (8)
背景知识 (9)
原文
Why Snakes Have Forked Tongues
①The forked tongue of snakes has intrigued people for millennia,inspiring many hypotheses.In many cultures and religions,the forked tongue symbolizes malevolence and deceit.The first person known to inquire about the functional significance of the forked tongue was Aristotle;he suggested that it would double the pleasure of sensations of taste.By the beginning of the twentieth century,the consensus was that the snake’s tongue is a tactile organ;that is,the snake uses it to tap the ground much as a blind person uses a cane.
②In1920Browman suggested what seemed to be a winning hypothesis:When the snake retracts its tongue,the tips(or tines)of the forked tongue are inserted into openings on both sides of the roof of the mouth;through these openings chemical stimuli reach special organs that help snakes detect smells—the vomeronasal organs(VNO).These organs are highly developed in snakes,lizards, and many mammals.They are a second system for detecting smells that appears to have evolved specifically to detect pheromones,the chemical signals that animals secrete as messages to other animals of their species.Browman suggested that the forked tongue flicks out,picking up chemical signals,and then delivers these to the VNO.This hypothesis was widely accepted into the1980s.Then X-ray movie studies of tongue flicks in snakes and lizards with forked tongues disproved the hypothesis;they showed that when the tongue is withdrawn into the mouth,it enters a sheath and the tips do not go into the openings to the VNO.Instead,the chemical molecules are deposited on pads at the bottom of the mouth,and closing the mouth presses the pads and molecules against the VNO openings.
③If the tongue is not forked to fit into the VNO,then what function could the forked shape serve?Schwenk proposes a solution that encompasses observations from several fields—animal behavior,ecology,sensory physiology,and neuroanatomy.He hypothesizes that the forked tongue allows the snake to sense chemical stimuli at two points simultaneously,thereby giving it the ability to detect differences in an odor trail.Obtaining two simultaneous readings enhances the ability of the snake to detect the edges of odor trails,and thus to follow pheromone trails accurately.This ability is important in seeking both prey and mates.
④This spatial chemical perception is like other systems for spatial perception that are based on simultaneous stimulation of two separated sense organs—for example,auditory localization,which depends on differential stimulation at the two ears.Similarly,the use of the two eyes permits stereovision.
⑤Several kinds of evidence support the hypothesis that forked tongues evolved as chemosensory edge detectors to enhance the ability to follow odor trails:(1) Snakes and lizards spread the tines of their tongue apart when they retrieve odor molecules,then draw the tines together when retracting the tongue.The greater the distance between sampling points,the better the animals sample differences within an odor trail.(2)Lizards that forage widely have forked tongues,whereas lizard species without forked tongues tend not to forage widely.(3)Forked tongues have evolved independently at least twice in different families of reptiles, indicating their value as an adaptation.(4)In the snake nervous system,each tine of the tongue is linked to a nucleus in the other side of the brain,and the two nuclei are linked across the two hemispheres.This arrangement is similar to the anatomy of auditory centers in mammals and birds that permits the computation of differences between what one ear hears and what the other ear hears and thus mediates auditory localization.
⑥Species in other orders have also evolved paired chemical receptors to guide individuals to mates or prey.For example,male gypsy moths have large,elaborate, odor-detecting antennae with which they track potential mates over large distances,and the ant nest beetle has spoon-shaped antennae extending from each side of the head with which it detects and follows the pheromones of the ants that are its food.
译文
为什么蛇有叉状舌头
①蛇的叉状舌头吸引了人们数千年，激发了许多假设。

在许多文化和宗教中，叉状的舌头象征着恶意和欺骗。

已知最早探究叉舌功能意义的人是亚里士多德，他认为这将使味觉愉悦感加倍。

到20世纪初，人们一致认为蛇的舌头是一种触觉器官；也就是说，像盲人用拐杖一样，蛇用它的舌头来敲击地面。

②1920年，Browman提出了一个似乎是成功的假设：当蛇缩回舌头时，将分叉舌头的尖端（或尖齿）插入嘴顶两侧的开口中，通过这些开口，化学刺激物到达帮助蛇检测气味的特殊器官，即犁鼻器（VNO）。

这些器官在蛇，蜥蜴和许多哺乳动物中非常发达。

它们是第二种用于检测气味的系统，该系统似乎是专门为检测信息素而开发的，信息素是动物分泌给其同伴的化学信号。

Browman认为叉状舌头会弹起，拾取化学信号，然后将其传递给VNO。

这个假设在1980年代被广泛接受。

然后，关于蛇和蜥蜴用分叉的舌头轻弹舌头，用X射线电影研究反驳了这一假说；他们的研究表明，当舌头缩入口腔时，它会进入护套，而尖端不会进入VNO的开口。

相反，化学分子沉积在嘴底的垫片上，并且闭合嘴部将垫片和分子压在VNO开口上。

③如果没有将舌头叉入VNO中，那么叉形起到什么作用呢？Schwenk提出了一种解决方案，其中包括来自多个领域的观察结果—动物行为，生态学，感觉生理学和神经解剖学。

他假设分叉的舌头允许蛇同时在两个点上感知化学刺激，从而使它能够检测到气味踪迹的差异。

同时获得两个读数可增强蛇检测气味踪迹边缘的能力，从而准确地跟踪信息素踪迹。

这种能力对于寻找猎物和伴侣都很重要。

④这种空间化学感知就像其他空间感知系统一样，是基于对两个分离的感官器官的同时刺激，例如，听觉定位，这取决于两只耳朵的差异刺激。

同样地，两只眼睛的使用可实现立体视觉。

⑤有几种证据支持这样的假说，即分叉的舌头演变成化学感应边缘检测器，以增强跟随气味踪迹的能力：（1）蛇和蜥蜴在回收气味分子时将其尖齿分开，然后在缩回舌头时将它们拉在一起。

采样点之间的距离越大，气味踪迹内的动
物采样差异就越好。

（2）广泛觅食的蜥蜴有分叉的舌头，而没有分叉舌头的蜥蜴往往不会广泛觅食。

（3）分叉的舌头在不同的爬行动物家族中至少独立地进化了两次，表明它们具有适应性。

（4）在蛇的神经系统中，舌头的每个尖齿都与大脑另一侧的一个核相连，而两个核则在两个半球之间相连。

这种结构类似于哺乳动物和鸟类的听觉中心的解剖结构，该结构允许计算一只耳朵听到的声音与另一只耳朵听到的声音之间的差异，从而介导听觉定位。

⑥其他的物种也进化了成对的化学受体，以引导个体进行交配或捕食。

例如，雄性吉普赛蛾具有大而精致的气味检测触角，通过它们可在很长的距离上追踪潜在的配偶，而蚁巢甲虫则具有从头部的每一侧延伸出的勺状触角，用以检测并跟踪蚂蚁的信息素。

题目
1.The word“secrete”in the passage is closest in meaning to
A.hide
B.intend
C.produce
D.collect
2.According to paragraph2,what was discovered as a result of X-ray movie studies of snakes and lizards?
A.The two tines of the forked tongue flick out to pick up chemical signals.
B.VNO are highly developed in snakes and lizards.
C.Snakes and lizards cannot accurately detect the pheromones of animals of other species.
D.The snake's tongue deposits chemical molecules on pads at the bottom of the snake's mouth.
3.The word“simultaneously”in the passage is closest in meaning to
A.in a similar manner
B.at the same time
C.at some distance from each other
D.with great skill
4.According to Schwenk's hypothesis as presented in paragraphs3and4,what is theadvantage of a snake’s forked tongue?
A.A forked tongue increases the reliability of odor perception because each tine can function as a check to confirm what the other tine senses
B.Having a forked tongue,like having two ears or eyes,has the advantage that if one tine becomes disabled the snake can still perceive the environment with the other tine.
C.With a forked tongue,one tine is able to sense the odor of a mate,while at the same time the other tine can be used to track a prey animal.
D.A forked tongue allows a snake to follow pheromone trails accurately by detecting differences between the two slightly different areas that the left and right tines sense.
5.According to paragraph5,snakes and lizards are greatly aided in following odortrails by
A.sampling odor trails only when they stop moving
ing their forked tongue to check information from other sensory detectors
C.keeping the tines of their tongue widely apart when retrieving odor molecules
D.folding the tines of the tongue together when withdrawing it into the mouth
6.Which of the following is presented in paragraph5as evidence supporting the hypothesisthat forked tongues evolved to enhance the ability to follow odor trails?
A.The forked tongue adaptation has evolved separately more than once.
B.How far snakes and lizards spread the tines of their tongues depends on the type of odor trail they are following.
C.There are many more lizard species with forked tongues than without forked tongues.
D.In snakes,the chief value of the forked tongue is in finding a mate.
7.It can be inferred from paragraph5that the tines of the tongue in snakes areconnectedto the nervous system in such a way that
A.the tines also serve as the snakes’means of auditory localization
rmation about which signal came from which tine is eventually lost
C.a comparison between what one tine picks up and what the other tine picks up is possible
D.the two hemispheres of the brain contain exactly the same sensory information
8.Why does the author talk about“gypsy moths”and the“ant nest beetle”?
A.To emphasize that the search for mates and prey is often a matter of following odor trails
B.To point out that chemosensory perception in snakes and lizards is not very highly developed
C.To make the point that snakes and lizards are not unique in having paired chemical receptors
D.To show that the work done by the forked tongue is more typically done by special antennae
9.Look at the four squares[■]that indicate where the following sentence could be added to the passage.Where would the sentence best fit?Click on a square[■]to add the sentence to the passage.
In other words,lizard tongues are forked precisely in cases where being able to follow odor trails is an advantage..
⑤Several kinds of evidence support the hypothesis that forked tongues evolved as chemosensory edge detectors to enhance the ability to follow odor trails:(1) Snakes and lizards spread the tines of their tongue apart when they retrieve odor molecules,then draw the tines together when retracting the tongue.The greater the distance between sampling points,the better the animals sample differences within an odor trail.[■](2)Lizards that forage widely have forked tongues, whereas lizard species without forked tongues tend not to forage widely.[■](3) Forked tongues have evolved independently at least twice in different families of reptiles,indicating their value as an adaptation.[■](4)In the snake nervous system,each tine of the tongue is linked to a nucleus in the other side of the brain, and the two nuclei are linked across the two hemispheres.This arrangement is similar to the anatomy of auditory centers in mammals and birds that permits the computation of differences between what one ear hears and what the other ear hears and thus mediates auditory localization.[■]
10.Directions:An introductory sentence for a brief summary of the passage is provided plete 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.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
In the1980s Browman’s widely accepted theory of why snakes have forked tongues was proven to be untrue.
A.As snakes and lizards have evolved,there have been shifts in the function of their forked tongue.
B.Browman’s hypothesis was replaced by the hypothesis that forked tongues function as organs of spatial chemical perception.
C.The readings obtained by each tine are processed separately and can thus be
compared,a feature shared by other systems of spatial perception.
D.X-ray movies showed that the chemical molecules picked up by the tines cannot be processed by the VNO because pads at the bottom of the snake’s mouth press against the VNO openings.
E.The tines are a pair of sensory organs that allow snakes to detect the edges of odor trails laid down by prey or potential mates.
F.Snakes have a pair of special sensory organs in their heads that produce chemicals that they use in laying odor trails.
答案
1-5.C D B D C
6-9.A C C B
10.BCE
小结题解析
A选项shifts in the function of their forked tongue未提及，错误；
B选项Browman’s hypothesis对应第2段，replaced by the hypothesis that forked tongues function as organs of spatial chemical perception对应第3段Schwenk提出的假说，概括两段内容，正确；
C选项The readings obtained by each tine are processed separately and can thus be compared对应第5段，a feature shared by other systems of spatial perception 对应第4、5段，正确；
D选项对应第2段，但是文中细节，不符合主旨选项要求，错误；
E选项对应第3段，正确；
F选项that produce chemicals that they use in laying odor trails未提及，错误。

故选BCE。

背景知识
蛇的舌尖为什么会分叉？
蛇是一类特殊的爬行动物，它们的舌头与大多数其他动物的舌头不同，因为蛇的舌头会分叉。

为了解释蛇的舌尖为什么会分叉，聚师网小师兄表示可以从蛇的嗅觉器官、运动机能和生态适应性几个方面进行解释。

首先，蛇的舌头分叉可以增强它们的嗅觉能力。

蛇是一类拥有高度发达的嗅觉系统的动物，在狭小的环境中通过嗅觉来获取食物、寻找伙伴和感知环境信息。

蛇使用舌头来收集空气中的化学信号，并通过舌尖上特殊的嗅觉器官来解读这些信号。

分叉的舌头可以增加舌头表面的接触面积，从而增强蛇对环境中化学信号的感知能力。

当蛇伸出舌头时，舌尖分叉的形态可以使舌头更好地捕捉周围空气中的气味分子。

其次，蛇的舌尖分叉还可以帮助它们在环境中更好地定位和感知。

蛇的分叉舌头通过移动和颤动来获取更多的嗅觉信息。

当舌头伸出时，蛇会震动舌尖，这样可以让气味分子粘附在舌头的湿润表面上。

然后蛇会将舌头收回嘴中，并通过与位于蛇口腔内的Jakobson器官（一种与食物储存区域相关的嗅觉器官）相互接触，以解读捕获到的气味信息。

通过舌尖分叉，并与嘴中内腔结构的相互
联系，蛇可以更准确地感知气味的来源和方向，帮助它们定位和捕捉猎物。

此外，蛇的舌头分叉还与它们的生态适应性有关。

蛇栖息在各种不同的环境中，包括沙漠、森林和湿地等。

分叉的舌头能够适应这些不同环境中的气味信息。

在一些高温、干燥或有毒气体的环境中，蛇可以利用分叉舌头来感知食物和危险。

最后，蛇的舌尖为什么分叉还与蛇的运动机能有关。

分叉舌头具有柔软和灵活的特点，可以随着蛇的身体运动而灵活摆动。

这使得蛇在狭窄的地方行动时，可以通过摆动舌头获取周围环境的嗅觉信息，有助于蛇避免与障碍物碰撞和捕捉食物。

总而言之，蛇的舌头分叉是一种独特的生物特征，它与蛇的嗅觉能力、环境适应性和运动机能密切相关。

聚师网小师兄表示分叉的舌头增加了蛇的嗅觉感知能力，舌尖的震动和分叉结构使蛇能够更精确地定位和感知环境中的气味。

蛇的分叉舌头是自然选择长期演化的结果，使得蛇能够更好地适应复杂多变的环境中的生存和捕食需求。