OK, so we’ve been looking at how man-made changes in our environment can affect wildlife. Now I’ll discuss a particular example. Let’s take a look at mercury. Mercury’s one of the 120 or so elements that make up all matter, and it has the symbol Hg. It’s a shiny, silvery substance. You may have seen it in old-fashioned thermometers, but it’s not used much for domestic purposes now because it’s highly toxic.
But the problem is that the amount of mercury in the environment’s increasing. The main reason for this is the power plants used to produce electricity. The main source of energy that most of them use is still coal, and when it’s burned it releases mercury into the atmosphere. Some of this gets deposited into lakes and rivers, and if it’s ingested by a fish it’s not excreted, it stays in the fish’s body and it enters the food chain. So it’s been known for some time that birds which eat fish may be affected, but what wasn’t known until quite recently is that those that eat insects can also be affected. 【Q31】
So a woman called Claire Varian-Ramos is doing some research on how this is affecting birds.
And rather than looking at how many birds are actually killed by mercury poisoning, she’s looking for more subtle sub-effects. And these may be to do with the behaviour of the birds, or with the effect of mercury on the way their brain works, so whether it leads to problems with memory, for example 【Q32】. And she’s particularly focusing on the effects of mercury on bird song. Now, the process of song learning happens at a particular stage in the birds’ development, and what you may not know is that a young bird seems to acquire this skill by listening to the songs produced by its father 【Q33】, rather than by any other bird.
And Varian-Ramos has already found in her research that if young male birds are exposed to mercury, if they eat food contaminated with mercury, then the songs they produce aren’t as complex as those produced by other birds 【Q34】. So quite low-level exposure to mercury is likely to have an impact on male birds in a natural situation, because it can mean that they’re less attractive to female birds, and so it can affect their chances of reproduction. 【Q35】
Now the way she’s carrying out this research is worth thinking about. She’s using a mixture of studies using birds kept in laboratories, and studies carried out outdoors in the wild. The lab-based studies have the advantage that you don’t get all the variables you would in a natural setting, so the experimenter has a much higher level of control 【Q36】, and that means they can be more confident about their results in some ways. And of course they don’t have to worry about going out and finding the birds in order to observe them.
So what are the implications here for humans? Well, because many birds are migratory, they may be transporting mercury far from contaminated sites. For example, it’s been found that ducks who’d been feeding at a contaminated site were later shot by hunters over a thousand kilometres away, and presumably eaten 【Q37】. But these birds likely had mercury levels high enough to warrant concern for human consumption.
In addition, going back to song learning by birds, we saw that this may be affected by mercury contamination. Well, we also know that in humans, mercury causes developmental delays in the acquisition of language 【Q38】, and in fact this process is very similar in the brain regions it involves and even the genes that are involved. But mercury contamination has other important implication for humans as well. It’s now known that an unborn child can be affected if the food eaten by its mother contains high levels of mercury 【Q39】, and these effects can be quite substantial.
In the end, it comes down to whether more value is placed on human economic wellbeing or environmental wellbeing. It’s true there are new regulations for mercury emissions from power plants, but these will need billions of dollars to implement, and increase costs for everyone 【Q40】. Some argue that’s too much to pay to protect wildlife. But as we’ve seen, the issues go beyond that, and I think it’s an issue we need to consider very carefully.
Complete the notes below.
Write ONE WORD ONLY for each answer.
听前预测：定位词 feed on；提示词 recently、affect、birds、also。此处应填某种比鸟类更小的生物类名词。
题目解析：我们首先听到了 fish、affected，紧接着出现了关键的转折连词 but，之后带出了答案对应信息“what wasn’t known until quite recently is that those that eat insects can also be affected”，这句话中我们听到了大部分提示词的重现，且 eat 对应题干 feed on，这个属于常见的同义替换，因此答案为 insects。
听前预测：定位词 investigating、effects、birds’；提示词 or、mental processes、e.g.、memory。此处应填名词，且这个单词应该和 mental processes 为并列关系。
题目解析：我们首先听到了“she’s looking for…”，对应题目上一行的 investigating，然后出现了一个并列信息“the behaviour of the birds, or with the effect of mercury on the way their brain works”，其中 the way their brain works 对应题干 mental processes， behaviour of the birds 同 birds’ behaviour，因此答案为 behaviour 或 behavior。注意所有格 one’s sth. 常见的同义替换为 sth. of one。
听前预测：定位词 bird song；提示词 effects、bird’s、learned from。此处应填名词。
题目解析：首先我们听到了 effects、bird song 等词，然后再次听到 song learning，之后便出现了答案对应信息“and what you may not know is that a young bird seems to acquire this skill by listening to the songs produced by its father, rather than by any other bird”，其中 acquire by 对应 learned from，its 对应 a bird’s，因此答案为 father。另外，请注意在 A rather than B 的结构中，我们要选 A，而不是 B。
听前预测：定位词 exposed to mercury；提示词 songs、less。此处应填形容词，重点听比较级或者比较关系中的形容词。
题目解析：我们首先听到定位词 exposed to mercury，然后听到“then the songs they produce aren’t as complex as those produced by other birds”，其中 not as+ adj.+ as 就是题干 less+adj. 的同义替换，因此答案为 complex 或其同义表达 complicated。
听前预测：定位词 negative effect；提示词 this、may、on、birds’。此处应填名词。
题目解析：做这道题目的关键在于理解题目中 this 指代的是上面整行的信息（受水银影响的鸟唱的歌没那么复杂），然后我们听到了 impact，对应 negative effect，然后出现了答案“so it can affect their chances of reproduction”，其中 affect 对应 negative effect，因此答案为 reproduction（或其同义表达 breeding）。注意此处所有格再次被替换成 sth. of one 的形式。
听前预测：定位词 experimenter；提示词 allow、more。此处应填名词。
题目解析：这道题目比较简单，我们在定位词 experimenter 之后很快就听到了答案对应信息“so the experimenter has a much higher level of control”， 其中 has a much higher level of 对应题干 allow more，因此答案为 control。
听前预测：定位词 Migrating birds；提示词 such as、eaten by humans、mercury。此处应填表示某一种鸟类的名词。
题目解析：我们在听到 birds、migratory、mercury 等词之后听到了 for example，其对应的刚好是答案前面的 such as，接下来我们可以很快地找到一个唯一表示动物的名词 ducks，这个就是正确答案。无语法限制下，单数也算对。
听前预测：定位词 causes problems；提示词 Mercury、also、learning。此处应填名词。
题目解析： 我们在听到 also 这个表示并列结构的逻辑连词之后，出现了答案对应信息“mercury causes developmental delays in the acquisition of language”，其中 developmental delays 对应 problems，acquisition 对应 learning，因此答案为 language。
听前预测：定位词 mother、unborn child；提示词 from、may、affect。此处应填名词。本题解题的关键在于通过 from 判断出我们要听的是母亲身体里水银的来源，所以答案应该是一个表示什么东西的实意名词。
题目解析：本题定位词、提示词和答案一起出现，具体对应的原文信息为“an unborn child can be affected if the food eaten by its mother contains high levels of mercury”，其中 题干 A may affect B 的结构在原文中换成了 B can be affected by A，food eaten by its mother contains…mercury 对应 mercury in a mother’s body from food，因此答案为 food。
听前预测：定位词 mercury emissions；提示词 New regulations、everyone。此处应填名词。
题目解析：我们先是听到了 new regulations 和 mercury emissions，然后听到了答案的解题关键——转折连词 but，but 之后的信息通常为答案对应信息“but these will need billions of dollars to implement, and increase costs for everyone”，其中 these 指代的是前面“关于水银排放的新规定”，increase 对应 affect，costs for everyone 等于题干everyone’s…costs，因此答案为 costs。一般情况下，建议填写原文原词，判卷不严情况下，costs 的同义表达 prices/bills 也算对，且无语法限制时单数也可。
