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58-TPO57-听力解析-听力文本-Track4 Listening lecture2 script

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发表于 2017-6-29 16:59:51 | 显示全部楼层
Lecture 2
M) Listen to part of a lecture in a biology class.

F) Professor: We’ve been discussing predator-prey relationships. Will someone summarize what we went over last class?

Male Student: We focused on camouflaging where a species tries to blend it with its surroundings in order to hide from predators. You gave us examples like the octopus. Octopuses can change the color and even the texture of their skin to blend in really well with their environment.

Professor: Okay, and today I will talk about another type of adaption: mimicry. Nothing fancy about the term here, mimicry—to mimic. Just means to imitate. In biology, a group of organisms, called mimics, can develop a trait of behavior that imitates the appearance, the behavior, sound or scent of another species. Unlike with camouflage, the goal of mimicry is not to blend into its surrounding, the goal is to be mistaken as some other species. Again, we’re talking about this in the context of predator-prey relationships.

Mimicry is usually used as a way for animals to avoid predation by disguising themselves as another species that looks unappealing or even dangerous. When something harmless imitates something dangerous, that’s Batesian mimicry. A basic example of Batesian mimicry: some flies have evolved to mimic the black and yellow stripes of bees to make themselves look more dangerous. Predators associate attacking bees with getting stung so they avoid bees. Flies mimicking bees want predators to think they can sting, but there are more complex cases.

We recently discovered a type of octopus off the coast of Indonesia that mimics not just one animal, but several. It’s the first and the only known species that can do this. Researchers found it impersonating two specific types of poisonous fish and one type of poisonous sea snake. It shifts its body shape, and its movements to resemble these toxic animals and when mimicking the sea snake which has yellow and black bands, the octopus also changes color to have these colored bands. This is evidence that it may decide which animal to mimic based on which predator is nearby.

Female Student: It’s actually a reason to turn itself into… I mean, choosing to look like a particular formin response to a particular threat?

Professor: Exactly, for instance, when there’s the threat of being attacked by a nearby damselfish, this octopus specifically chooses to mimic the sea snake, because the sea snake eats damselfish. Anyway, it’s a dramatic finding. The fact that it can take on multiple disguises suggests other species might have this capability too.

Okay, so much for Batesian mimicry. Now, some animals use mimicry for a different purpose. Researchers have been studying the margay, a small cat that lives in the Amazon jungle. One time, they noticed the margay mimicking the cry of baby tamarins, a type of monkey. Vocal mimicry itself isn’t unusual. But, it’s usually used to scare a predator’s species away. What’s odd is that in this case, the relationship is reversed. Margays prey on tamarins, so they don’t need to hide themselves or make themselves seem more dangerous. This margay instead tried to sound scared or threatened, to draw tamarins in close by sounding like a baby tamarin that’s being attacked. So it seems that rather than using mimicry to avoid the predator, margays are actually using it to attract their prey, to find their next meal. The researchers noted that the margays’ high-pitched squeals weren’t a very good imitation of a baby tamarin, but that the squealing sound attracted the attention of adult tamarins anyway. Still, none of the tamarins really sealed the trick. When tamarins got closer to the crying sound, they realized it was coming from the margay and escaped before they could be attacked.

Even so, that margays even use this technique suggests that they’ve had some success with it in the past. Maybe we were just observing them on an off day. And margays probably aren’t the only cat species in the Amazon adopting sneaky strategies. People who live in the Amazon have said that they’ve heard other cat species like tigers or cougars tricking their prey this way. But those are just anecdotal reports and they still have to be confirmed by researchers. This type of mimicry may not be an innate, inborn trait. Margay moms may teach it to their young, so it’s possible that not all margays have this capability. It might just be a learned behavior kept within families.
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发表于 2017-8-8 19:07:20 | 显示全部楼层
我只是来下资料的。
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发表于 2017-8-9 09:39:27 | 显示全部楼层
待我长发及腰,我来下载资料可好。
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发表于 2017-8-9 09:47:58 | 显示全部楼层
你造么,资料下载,根本停不下来
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发表于 2017-8-9 09:51:35 | 显示全部楼层
资料下载是真爱,转身的时候就该留下,
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发表于 2017-8-9 09:51:42 | 显示全部楼层
卧槽,我居然看完了,我竟然下载了。
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发表于 2017-8-15 17:31:44 | 显示全部楼层
有了这个资料就可以省好多钱欸~~下载来好好学习~
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发表于 2017-8-22 17:54:52 | 显示全部楼层
哇塞,谢谢楼主分享资料,下载很方便,分享最美丽
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发表于 2017-8-30 16:12:53 | 显示全部楼层
我想肯定会有人数这句话有多少字
如果你真的不知道有这句话的存在
想要下载必先回帖资料终于到手了
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发表于 2017-9-7 17:16:30 | 显示全部楼层
楼主真是文笔极佳,才思敏捷,过目不忘,十年寒窗,博学多才,见多识广,才高八斗,学富五车,文武双全,雄韬伟略,谈吐不凡,谈笑风声,高谈阔论,眉飞色舞,运筹帷幄, 言简意赅, 一针见血 远见卓识,义正词严, 一气呵成, 大显神通,出口成章,出类拔萃,出神入化,万古流芳的大学士,为了追随楼主的步伐我已下载完楼主发的资料。
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