Animal Navigation System托福听力原文翻译及问题答案

Animal Navigation System托福听力原文翻译及问题答案

一、Animal Navigation System托福听力原文：

NARRATOR:Listen to part of a lecture in an animal behavior class.FEMALE PROFESSOR:Before we leave the topic of animal navigation,let's look at one more species and how it finds its way through its environment.The species we'll look at is the blind mole rat.Blind mole rats are interesting in terms of navigation because they live entirely in the dark-in elaborate underground tunnel systems.So how do blind mole rats find their way around in these complicated tunnels?Well,for some time we've known that blind mole rats use some combination of two different navigation systems.

Um,one system relies on their sense of time and their ability to remember underground landmarks.For example,let's say a mole rat wants to find its way through its tunnel system back to its nest where it sleeps.Well,it goes along.Then it feels some hard stones or a tree root under its feet and it basically says to itself."Ok,here is where I took a left."And then it might remember how long it took to get to the next turn and so forth.The mole rat goes straight or turns based on what it remembers having sensed along the way on previous trips and the time it took between turns.Now,the other navigation system for the mole rat relies on Earth's magnetic field.Mole rats have the ability to sense the magnetic field and use it to orient themselves directionally.But until recently scientists weren't sure about the role of these two different systems.

Recently a team of researchers conducted an experiment to answer that question.Do these two navigation systems play different roles?What they did was they designed a special structure that very closely resembles a blind mole rat's tunnel system,which looks like a bicycle wheel,a central hub with multiple spokes radiating outward.

Now this turned out to be quite important.Earlier experiments have used a more generic habitat,basically a wide open circle,which was originally designed to test magnetic navigation in other animals.That design led to inconclusive results with mole rats.

Now,with their bicycle wheel tunnel system the researchers were able to vary the distance that the mole rats travel between their nest and their food source by creating long routes and short routes.In each trial,the mole rats started out in their nest,went to the food source and then had to find their way back home,back to the nest.To determine which navigation system they were using,the researchers tested the animals under two different conditions.

First,the mole rats were tested under conditions of normal magnetism for both the trip to the food and the trip home.And under these normal conditions,they all followed their original route back home,regardless of the length of the trip to the food source.

Then in the second part of the experiment,the magnetic field was altered but only for the trip home,a specially constructed set of magnets was used to shift the magnetic field around the habitat 90 degrees eastward.The researchers wanted to see how the mole rats responded to this shift.Well,it turns out that the magnetic shift had no impact on the return route of the blind mole rats after a short trip.They returned to the point where they had started from.

But after a longer trip,they took a totally different route:one that led them nine degrees east of the nest.Essentially they got lost.This was strong evidence that blind mole rats use magnetic navigation only for longer trips.So why two navigation systems?one for long trips and one for short trips?

Well,for now we can only speculate,but we think that when mole rats rely on the first system,using underground landmarks or their sense of time,well,they make small mistakes here and there.On a short trip,this doesn't matter much.The trip is short,so they can't make many mistakes.

But on a long trip,well,there are lots of opportunities to make small mistakes,and small mistakes can add up,leading the mole rat far from where it wants to be.So on a long trip,a magnetic navigation system is better,more useful,since earth's magnetic field is stable,a constant,a more reliable indicator of direction.

二、Animal Navigation System托福听力中文翻译：

旁白：在动物行为课上听一部分讲座。女教授：在我们离开动物导航的话题之前，让我们再看一个物种，看看它是如何在环境中找到自己的路的。我们要研究的物种是盲鼹鼠。盲鼹鼠在导航方面很有趣，因为它们完全生活在黑暗中，生活在复杂的地下隧道系统中。那幺，盲鼹鼠是如何在这些复杂的隧道中找到自己的路的呢？一段时间以来，我们知道盲鼹鼠使用两种不同导航系统的组合。

嗯，一个系统依赖于他们的时间感和记忆地下地标的能力。例如，假设一只鼹鼠想通过它的隧道系统找到自己的路，回到它睡觉的巢穴。嗯，它一直在发展。然后它感觉到脚下有一些坚硬的石头或树根，它基本上会自言自语。“好吧，这是我左转的地方。”然后它可能会记得到下一个转弯需要多长时间，等等。鼹鼠根据它记忆中在之前的旅程中所感知到的东西和它在两次转弯之间所用的时间，走直线或转弯。现在，鼹鼠的另一个导航系统依赖于地球磁场。鼹鼠有能力感知磁场并利用磁场定向。但直到最近，科学家们还不确定这两种不同系统的作用。

最近，一组研究人员进行了一项实验来回答这个问题。这两个导航系统的作用不同吗？他们所做的是设计了一种特殊的结构，非常类似于盲鼹鼠的隧道系统，它看起来像一个自行车车轮，一个中心轮毂，多个辐条向外辐射。

现在这证明是非常重要的。早期的实验使用了更通用的栖息地，基本上是一个开阔的圆，最初设计用于测试其他动物的磁导航。该设计导致了对鼹鼠的非决定性结果。

现在，通过自行车轮隧道系统，研究人员能够通过创建长路线和短路线来改变鼹鼠在巢穴和食物来源之间的距离。在每一次试验中，鼹鼠都从巢穴开始，找到食物来源，然后必须找到回家的路，回到巢穴。为了确定他们使用的是哪种导航系统，研究人员在两种不同的条件下测试了这些动物。

首先，在正常磁性条件下对鼹鼠进行食物和回家的测试。在这些正常的条件下，他们都按照原来的路线回家，不管去食物来源的路程有多长。

然后，在实验的第二部分，改变了磁场，但仅在回家的路上，使用了一组特殊构造的磁铁，将栖息地周围的磁场向东移动90度。研究人员想知道鼹鼠对这种变化的反应。事实证明，磁位移对盲鼹鼠短暂旅行后的返回路线没有影响。他们回到了起点。

但经过一次长途旅行后，它们选择了一条完全不同的路线：一条通向鸟巢以东九度的路线。基本上他们迷路了。这有力地证明，盲鼹鼠只在长途旅行中使用磁导航。那么，为什么有两个导航系统？一个用于长途旅行，一个用于短途旅行？

嗯，现在我们只能推测，但我们认为当鼹鼠依靠第一个系统，利用地下地标或他们的时间感时，他们会犯一些小错误。在短途旅行中，这并不重要。旅程很短，所以他们不会犯很多错误。

但是在长途旅行中，会有很多机会犯小错误，小错误加起来会导致鼹鼠远离它想去的地方。所以在长途旅行中，磁导航系统更好，更有用，因为地球磁场是稳定的，恒定的，更可靠的方向指示器。

三、Animal Navigation System托福听力问题：

Q1:1.What is the lecture mainly about?

A.The structure of the blind mole rats'underground tunnel system

B.How blind mole rates find their way back to their nests

C.Whether some animals use Earth's magnetic field for navigation

D.Whether blind mole rats have more than one navigation system

Q2:2.Why does the professor mention tree roots and rocks?

A.To emphasize the blind mole rat's need for two navigation systems

B.To explain one reason why blind mole rats get lost

C.To give examples of landmarks used by the blind mole rat

D.To describe the materials the blind mole rat uses to build its nest

Q3:3.In discussing the experiment,why does the professor refer to a generic habitat?

A.To prevent a misunderstanding about blind mole rats'tunnel systems

B.To indicate how the researchers found the animals for the experiment

C.To describe similarities between blind mole rats'natural habitat and those of other animals

D.To emphasize the importance of habitat design to the success of the experiment

Q4:4.What did the research team modify in the second part of their experiment?

A.They removed the food from the habitat.

B.They increased the distance between the nest and the food source.

C.They changed the magnetic field around the habitat.

D.They shifted the location of obstacles in the tunnels.

Q5:5.According to the professor,what factor governs which navigation system the blind mole rat uses in a given situation?

A.The distance traveled

B.The direction of travel

C.The complexity of the tunnel system

D.The presence or absence of landmarks

Q6:6.What does the professor imply when she explains why blind mole rats use two navigation systems?

A.One system is more accurate than the other for long trips.

B.One system takes more time to use than the other one does.

C.Individual blind mole rats have a preference for on system or the other.

D.Animals usually do not rely on only one navigation system for long trips.

四、Animal Navigation System托福听力答案：

A1:正确答案：B

A2:正确答案：C

A3:正确答案：D

A4:正确答案：C

A5:正确答案：A

A6:正确答案：A

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