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新东方网为大家带来2020托福听力练习：聪明的蚂蚁备份导航系统（下载），希望对大家有所帮助!更多内容请随时关注新东方网!
Make a left at the big oak tree about a mile down the road. That kind of direction is common in landscapes filled with visual cues. But the Sahara desert is a much tougher place to navigate. Even any footprints you leave get erased as winds massage the sand. Nevertheless, ants in the desert go on searches for food—and once they find it they carry their prize directly back to the nest.
In the late 1980's, researchers discovered that the ants can achieve this impressive feat using a process called path integration. To gauge the direction home, they keep track of the sun's motion across the sky—just like sailors used to do. To calculate the distance, they count their steps.
"It's a very hostile environment. They're foraging at the hottest times of the day and it's a desert, so surface temperatures reach 60 to 70 degrees Celsius."
Neurobiologist Matthias Wittlinger from Germany's Ulm University, on the podcast of the journal Science, which published this work.
"And they need to be really quick in finding food, and they really need to be very quick in getting the food back to the nest...they need to be really fast, and they're travelling at speeds of 100 body lengths per second."
Wittlinger noticed that sometimes desert ants carry each other.
"And here we had this unique opportunity to test traveling ants that are not walking."
If they're not walking, then they can't count their steps. So would these ants be able to find their way home?、
Bees and wasps can't count their steps, because they fly. Instead, to estimate distance they rely on what's called optic flow, which tracks how much visual information flows past them while they travel. So, do carried ants also use optic flow?
To find out, the researchers waited for an ant to emerge from its nest carrying another. After the pair walked for ten meters, the researchers separated them. And impressively, the carried ant marched straight on back to the nest—but not if their vision was blocked.
"So if they were blindfolded while being carried, they have no chance of gaining any distance information."
Which proves that they need eyesight—and therefore optic flow—to do it.
These critters live in one of the harshest environments on the planet, so it makes sense that evolution endowed them with the tools for path integration and optic flow.
"In the case of the desert ant, it's really important that they're getting navigation right...if one system fails, you still have a backup system."
Because if you're going to live in the desert you have to be very clever in finding ways to not die in the desert.
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沿着这条路走，在大约一英里处的大橡树那里左拐。这种导航方向在有视觉线索的地形非常常见。但是撒哈拉沙漠是一个很难导航的地方。即使你留下脚印也会被风沙覆盖。然而，在沙漠中的蚂蚁却能够继续寻找食物，一旦它们发现食物，它们可以直接把食物搬回巢穴中。
上世纪80年代后期，研究人员发现蚂蚁可以实现这一了不起的壮举，这被称为路径整合。蚂蚁跟踪太阳在天空中的运动情况来判断回家的方向，就像过去水手们做的一样。它们通过计算步数来计算距离。
“这是一个非常恶劣的环境。它们在一天最热的时间觅食，沙漠的表面温度高达60到70摄氏度。”
德国乌尔姆大学的神经生物学家马蒂亚斯·威特林格在本周《科学》期刊的播客上发表了这项研究成果。
“它们要快速找到食物，还要快速把食物带回巢穴……它们的动作要非常快，基本上它们每秒的速度要达到身长的100倍。”
威特林格指出，有时沙漠蚂蚁会互相背着前进。
“我们有这个独特的机会来测试那些没有走路的觅食蚂蚁。”
如果它们不走路，那它们就不能计算步数。那这些蚂蚁能找到回家的路吗?
蜜蜂和黄蜂不能数步数，因为它们靠飞行移动。所以，它们依靠光流来计算距离，它们会根据飞行过程中的视觉信息流来估算距离。那被抬着的蚂蚁也用光流来计算距离吗?
为了弄清楚这点，研究人员等待一只蚂蚁背着另一只蚂蚁从它的巢里出现。在它们走了十米以后，研究人员把它们分开了。令人印象深刻地是，如果视野受阻，那被背着的蚂蚁会径直返回巢穴中。
“如果它们在被背着时眼睛被蒙住，那它们就没有机会获得任何有关距离的信息。”
这证明它们需要视力，也就是要它们需要光流。
这些生物生活在地球最恶劣的环境中，所以进化赋予它们路径整合和光流的能力是有道理的。
“在沙漠蚂蚁的例子中，获得导航能力是非常重要的……如果一个系统失败，它们还有一个备份系统。”
因为如果要在沙漠中生活，你必须要非常聪明，这样才能找到路而避免死在沙漠中。
重点讲解：
1. keep track of 跟上…的进展;掌握…的最新消息;
例句：I keep track of my expenses in a notebook.
我把我的支出记在一个笔记本上。
2. rely on 依赖;依靠;
例句：In default of expert's help, you'll have to rely on yourselves.
没有专家的帮助，你们只好依靠自己了。
3. find out (尤指特意通过努力)发现，找出，查明;
例句：He was asked to find out how the land lies.
有人要他探知事情的真相。
4. make sense 可以理解;讲得通;
例句：Delaying their retirement by raising the pensionable age might make sense.
通过推迟拿养老金的年龄而让他们迟点退休，可能还有道理。
5. endow with 赋予;使天生拥有;
例句：You are endowed with wealth, good health and a lively intellect.
你生来就拥有财富、健康和活跃的思维。
以上是新东方网为大家带来的2020托福听力练习：聪明的蚂蚁备份导航系统（下载），希望认真积极的备考，早日取得优异的成绩。更多内容请随时关注新东方网!
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