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Part One:

You will hear the director of a college talking about his school. Listen to the talk and answer the questions. First, you have some time to look at questions 1 to 3.

Now we shall begin. You should answer the questions as you listen because you will not hear the recording a second time. Listen carefully and answer questions 1 to 3.

Many of you already have a reasonably firm idea of the general subject area you wish to study. Others are more open and searching for ideas. Whatever your situation, I hope you find that we have a course that meets your needs. Our firm aim is to be a student-centered institution with a special emphasis on flexibility. This begins with our attitude to access. We judge people on their motivation and commitment to study as much as, if not more than, formal qualifications. This is reflected in the quality and diversity of our student population. Some of our students come direct from sixth form or college.

Before you hear the rest of the conversation, you have some time to look at questions 4 to 10.

Now listen and answer questions 4 to 10.

Others are coming into higher education after a short or long gap from formal education. Some are seeking a specific set of skills with a particular job or profession in mind. Others are retraining or studying to give their careers a new direction or dimension. Some are learning about the very latest scientific, technological, and commercial knowledge. Others are stretching their minds on sensitive environmental, social, and cultural issues. Even a casual observation of the mix of our student body indicates that we're close to our aim of being a polytechnic for the whole community.

To meet our students' needs, we have 500 academic and a further 500 support staff committed to good quality teaching, high standards, and sensitive and sympathetic student care. We have probably the longest experience of understanding and dealing with the differing needs of a diverse student body.

I hope you'll find a suitable course at the Polytechnic College. If you want to come to the college and we consider you suitable, we'll do our best to find you a place. And when you're here, we'll work hard to make your experience enjoyable, stimulating, and educationally rewarding.

That is the end of part one. You now have half a minute to check your answers.

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Part Two:

You will hear a tour guide giving information about a shopping district. First, you have some time to look at questions 11 to 15. As you listen to the first part of the talk, answer questions 11 to 15.

This afternoon, we'll visit the city's shopping district. Several blocks in the area are closed to car traffic, and I know you'll enjoy walking around there. I'd like to give you an overview of the district now, since you'll be on your own once we get there.

You'll see on this map here that the shopping district consists of two streets: Pear Street, which runs north and south, and Cherry Street, which crosses Pear Street, right here. Let's start our tour here on Pear Street, where the star is. This star marks the Harbourview Bookstore. It's very popular among locals, as well as tourists. You can buy a range of books of local interest, as well as a variety of magazines and newspapers. It's directly across the street from the City Library, which is also worth a visit. It's in one of the oldest buildings in Johnston and contains, among other things, an interesting collection of rare books.

Now, moving up Pear from the bookstore toward Cherry, the next building on the left is the Pear Cafe. You'll notice it's right on the corner of Pear and Cherry streets. It's a great place to relax while enjoying a delicious cup of coffee or tea. You can talk with friends or read quietly. They have a variety of books and magazines available. From the windows of the cafe, you can look right across Cherry Street for a lovely view of City Gardens. It's a rather small garden, but it contains a variety of exotic plants and flowers.

Let's leave the cafe and cross Pear Street. On the opposite corner, we're at Caldwell's clothing store, which you might also want to visit. They sell both men's and women's fashions from countries around the world.

Continuing down Cherry Street, the next building on the right after Caldwell's is the souvenir shop. Stop in here to get maps and books about the local area, as well as t-shirts, shirts, and postcards with pictures of the city.

Now, we cross Cherry Street, and we're at the Art Gallery, one building down from the corner. Here you can see, and of course purchase, many fine paintings and sculptures by local artists. Let's keep going down Cherry Street toward the harbor. On the left, right after the gallery, is Harbor Park. It's a lovely place, and it's certainly worth spending some time there.

Before you hear the rest of the talk, you have some time to look at questions 16 to 20.

Now listen, and answer questions 16 to 20.

Harbor Park was built on land donated to the city by Captain Jones, a lifelong resident of this city. Captain Jones designed the park himself, and it was built in 1876. Exactly in the center of the park, a statue of Captain Jones was erected, and it's still standing there today. It shows Captain Jones on the bow of his ship.

After viewing the statue, you can follow the path that goes through the woods just behind. It will lead you to a lovely garden, in the middle of which is a fountain. This is a nice place to enjoy a few quiet moments. If you still feel like walking, continue on to the far end of the garden. There you'll find a wooden staircase, which will take you down to the harbor. You might enjoy the view of the boats from there. There's also a walking path along the water, which will eventually bring you back up to Cherry Street. You can see that there's plenty to do in this part of the city. The bus leaves at 1:30.

That is the end of part two. You now have half a minute to check your answers.

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Part Three:

You will hear a tutor and two students discussing the crop rice. First, you have some time to look at questions 21 to 24. Now listen carefully and answer questions 21 to 24.

Good morning, everyone. So, following on from our tutorial on European agriculture last week, Daisy and Eric are going to talk about the most commonly grown crop in Asia, which is, of course, rice.

Eric, can you tell us what you've been working on?

Yes, sure. We've been looking at the role of rice in a number of countries, how it's grown, and ways of increasing production. As I'm sure you know, rice is the staple diet throughout Asia, and, in fact, 90% of the world's rice is grown and eaten there. Daisy's got some background on that.

Well, rice was originally a wild plant that started out in the tropical regions of Asia. But there are literally hundreds of varieties today, each with different qualities. For instance, one will survive floods while another will grow in relatively dry conditions. A third has a really lovely smell. But wherever it grows, rice needs a lot of water.

What do you mean by a lot?

Well, it takes about 5,000 liters to get a kilogram of rice. This can be supplied either naturally or by irrigation. And as most rice-growing countries suffer from unpredictable weather, including drought, water management really is the key!

Research has become so important now that each rice-growing country in Asia has its own research institute, whether we're talking about Japan, China, or Bangladesh. And they're all coordinated by a group in the Philippines called the International Rice Research Institute.

Interesting.

Bangladesh, for instance, has been successfully using different rice varieties and fertilizers for 30 years, but because it's such a flat, delta country, it's very difficult for the water to drain away after the monsoon season, so they need to find special rice crops that can survive the floods. And with global warming, the situation is more urgent than ever.

Before you hear the rest of the discussion, you have some time to look at questions 25 to 30.

Now, I'd like to move on to our comparative study. As you can imagine, China is the world's biggest rice-producing country. Collectively, the Chinese people probably eat more than 3 billion bowls of rice every day. Quite a statistic.

Mmm.

Of course, rice plays an important cultural role, too. We then compared China to Thailand. You know, even though Thailand only has about 64 million people, it's the world's number one exporter of rice. Not China, as you might imagine.

Is that so?

Yes. They send their rice everywhere, in particular to Europe, as well as Africa and the Middle East. Apparently, the fact that jasmine rice is the most expensive type of rice in the world is one reason why Thailand's rice export industry is doing so well. People want something a bit different. And of course, Thailand is well-suited to rice growing, with good climatic conditions and lots of fresh water.

Going back to China for a minute, we should mention that at the Rice Research Institute in Huangzhou, they're working on ways of improving rice yields using less water.

By yields, you mean...

The amount they can grow?

Yes. They're trying to find ways to get more rice from less land, improve the taste, but also have other things in it besides carbohydrates, so that it's healthier, better for you.

Good idea, considering it's the staple food.

And then you've got Japan, which is totally self-sufficient when it comes to rice. This is basically because they have a high tariff on imported rice, so everyone buys the home-grown product, and they don't export much.

Yes. You know, even though rice is a kind of sacred crop there, consumption is only half what it was in the 1960s. This trend isn't evident in Thailand or China.

Interesting that you mentioned how rice is almost sacred in Japan, because I believe in Thailand it also plays an important cultural role.

Absolutely. They have the Royal Ploughing Ceremony every year, which the king always attends, and he actually scatters a new stock of seed to the farm.

That's interesting. So, the farmers have to scatter a new seed to the farmers, who pour into Bangkok for the event.

What about the global interest in organic farming? Is there such a thing as organically grown rice?

Yes, indeed, and the Japanese are getting quite a taste for it, apparently. There's an experimental farm near the city of Akita in the Japanese rice belt, famous for its sake, by the way, which has pioneered organic rice production, and now it's sold all across the country. It's a bit like the recent popularity of jasmine rice in Thailand, but that's sort of the export market, of course.

Interesting how attitudes change, isn't it?

That is the end of part three.

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Part Four:

You will hear a lecture's introduction to Insect Biology 101. First, you have some time to look at questions 31 to 40. Now, listen carefully and answer questions 31 to 40.

Good afternoon and welcome to Insect Biology 101. I'd like to begin this course with a few remarks about good insects. Bugs are all around us, and that's both a benefit and an annoyance. Sometimes maybe even serious harm.

First, let's talk about the good things that insects do for us. Probably the most important insect for humans, and maybe for all other life, is the bee. Bees help plants in the process of pollination and thus are necessary to most flowers and fruit-producing trees. That is, they carry pollen from male flowers to female. If it weren't for bees, we'd have very few food plants and no fruit either. In fact, there would be no we. No lesser thinker than Albert Einstein pointed out that, without bees, humanity would be dead within a year or less. We'd starve. It's that simple. That should maybe make us just a little humble.

A little less dramatic is the fact that bees also make the honey we eat. Moreover, they produce beeswax, which is useful in candles, and is also used as a first-rate furniture polish. Sure, these may not be vital to our lives, but they can serve as reminders of how important bees are. That's a point I keep coming back to in this course. Though, in all fairness, I should point out that butterflies aid in pollination as well as bees.

Now, here in Michigan, what's the worst part of summer? Yep, that's right, mosquitoes. But I'm talking about helpful insects, right? So, let's look at the dragonfly for a moment. First, if there were no dragonflies, there would be even more mosquitoes. Dragonflies mainly eat mosquitoes, and also a few other insects. Yes, that's right, they don't just fly around. And they also help to eliminate harmful insects. So, the next time you see a dragonfly, don't you dare kill it.

Now, let's talk a little about those harmful insects. Take the mosquitoes I just mentioned as an example. Not so many years ago, mosquitoes here in America weren't just annoying. Some were even deadly. They carried malaria and yellow fever. My own ancestor, the Confederate General John Bell Hood, lived through the worst battles of civil war, only to die at age 38 from yellow fever. A pest, not a bullet.

Well, besides the mosquitoes, in summer there is also a kind of insect that never seems tired. Right, that is the fly. Before I go on talking, I must mention an African fly called the tsetse fly, which feeds on blood and can cause serious diseases in the people and animals that it bites. Besides, it is still a bearer of sleeping sickness, which affects around 300,000 people every year in Africa, and can be treated only with toxic drugs that are hard to administer. Worse still, the drugs sometimes don't work.

Other insects, of course, destroy food crops. In China, for instance, locusts continue to be a danger to the harvest in some areas. Less important, but still annoying, moths eat people's clothes and dust mites slowly destroy carpets. Worse, but still in the home, termites or white ants eat wood, the wood of your house. If they are not stopped, they can eventually destroy the whole building. Usually, they seriously damage a building before anyone even knows. So, as we all know, insects can be a real trouble. So, what to do?

You can go ahead and start killing harmful insects. In the early decades after the communist revolution in China, Chairman Mao encouraged the people to swat every fly they could see. Slogans on the walls of buildings called them little capitalists. But flies reproduced too quickly for this to be a long-term solution.

For some decades in the West, to kill insects with chemicals seemed a good remedy. Unfortunately, chemicals can only be used in a limited area for a limited time. It's a small-scale solution. The insects come back. Worse still, some of the poisons used, like DDT, were found harmful to the environment. Many kinds of wildlife, like hawks, were harmed. And people in chemical-using rural areas have one of the highest rates of liver cancer in the world. It's no secret that chemicals remain harmful to humans.

Like all species, insects adapt to their changing environments at an amazing rate. When a new chemical is introduced to their habitat, the insects that survive are generally the ones with some way of resisting the harmful effects. They then breed with the other survivors, and just like that, insects become resistant to most poison in a few generations. An insect generation, remember, is a couple of months at most.

So, again, we have to ask, what to do?

Well, there are biological solutions. Some of these are pretty simple. One is destroying the insect's habitat. You take away their home or food. Cleaning your kitchen is the best way to prevent roaches. No garbage, no food. Getting rid of marshes and swamps eliminates mosquitoes. Other solutions might include bringing in dragonflies or bats in areas where mosquitoes are many. This is a cheaper alternative to chemicals. Biological methods like this also bring no extra pollution to the environment. But you have to be careful. If you change the environment too much, you might be hurting other forms of life accidentally.

One recent method of controlling insect populations involves interrupting their breeding cycle. What does that mean? It means birth control for bugs. Insects are provided with food that makes them unable to reproduce. Since they can't have babies, the population disappears, or nearly so. And since no young are born, resistance is not a problem, with no young insects developing increased resistance. Interrupt the life cycle, eliminate the bug.

It's clear that we must have an understanding of the life cycle of the insect. At least, that's the plan. We'll go into more detail as the course goes along.

Now, I will stop here to see whether you have any questions or not.

That is the end of part four. You now have half a minute to check your answers.

 第一部分：

你将听到一位大学校长谈论他的学校。请听这段讲座并回答问题。首先，你有一些时间来看问题 1 到 3。

现在我们开始。你应该在听的过程中回答问题，因为你不会再听第二遍录音。请认真听并回答问题 1 到 3。

你们中的许多人已经有了一个相对明确的学习领域。其他人则更开放，正在寻找方向。不管你是哪种情况，我希望你能找到一门符合你需求的课程。我们的坚定目标是成为一个以学生为中心的机构，特别强调灵活性。这从我们对入学的态度开始。我们更看重学生的动机和学习承诺，而不是仅仅看重正式的资格证书。这一点在我们学生群体的质量和多样性中得到了体现。我们的学生中有些是从第六班或大学直接来的。

在你听到接下来的部分之前，你有一些时间来看问题 4 到 10。

现在请听并回答问题 4 到 10。

其他一些学生在短暂或长时间的间隔后才重新进入高等教育。有些人是为了获得特定的技能，以便从事某个特定的工作或职业。还有一些人正在重新培训，或者学习以使自己的职业朝新的方向或维度发展。有些人正在学习最新的科学、技术和商业知识。还有一些人在探索敏感的环境、社会和文化问题。从我们学生群体的组成来看，我们接近实现成为整个社区的多元化技术学院这一目标。

为了满足学生的需求，我们有500名学术人员和另外500名支持人员，致力于提供高质量的教学、保持高标准并提供细致入微的学生关怀。我们可能是理解并应对不同学生需求的经验最丰富的机构。

我希望你能在这所理工学院找到合适的课程。如果你想来学院，且我们认为你合适，我们会尽力为你找到一个位置。当你在这里时，我们将努力让你的经历既愉快又富有启发，并且教育意义深远。

第一部分到此结束。你现在有半分钟的时间检查你的答案。

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第二部分：

你将听到一位导游介绍一个购物区。首先，你有一些时间来看问题 11 到 15。在听到讲座的第一部分时，回答问题 11 到 15。

今天下午，我们将参观这个城市的购物区。该区域的几个街区禁止车辆通行，我知道你们会喜欢在那儿走来走去。现在我想先给大家概述一下这个购物区，因为你们到时会自行游览。

在这张地图上，你们会看到购物区由两条街道组成：一条是南北走向的梨街，另一条是与梨街交叉的樱桃街。我们的游览从梨街开始，星标指示了海港书店。这家书店在当地人和游客中都非常受欢迎。你可以购买各种本地相关的书籍，以及各类杂志和报纸。它正对着城市图书馆，值得一游。图书馆位于约翰斯顿最古老的建筑之一内，馆内收藏了许多珍贵书籍。

现在，从书店向樱桃街走去，左边的下一座建筑是梨咖啡馆。你会注意到它正好位于梨街和樱桃街的交叉口。这里是个放松的好地方，你可以一边享受美味的咖啡或茶，一边与朋友交谈或安静阅读。这里有各种书籍和杂志可以阅读。从咖啡馆的窗户看出去，你可以欣赏到樱桃街对面的美丽城市花园。它虽然不大，但拥有各种珍奇植物和花卉。

我们离开咖啡馆，穿过梨街，到了对面角落的考德威尔服装店，你也许会想去看看。这里销售来自世界各地的男女时尚。

继续沿着樱桃街走，考德威尔服装店之后的右侧是纪念品商店。可以到这里购买有关本地的地图和书籍，还有T恤、衬衫以及印有城市风景的明信片。

现在我们穿过樱桃街，来到了艺术画廊，离街角一座建筑的距离。在这里，你可以看到并购买许多本地艺术家的精美画作和雕塑。我们继续沿着樱桃街向港口走。左边，在画廊之后，是海港公园。这里是个非常漂亮的地方，绝对值得你在这里多待一会儿。

在你听到讲解的后半部分之前，你有一些时间来看问题 16 到 20。

现在请听，并回答问题 16 到 20。

海港公园建立在由约翰斯顿的终身居民琼斯船长捐赠的土地上。琼斯船长自己设计了这个公园，公园建成于1876年。公园中央竖立着琼斯船长的雕像，至今仍矗立在那里。雕像展现了琼斯船长站在自己船头的姿势。

在欣赏完雕像后，你可以沿着穿越树林的小路走去，它会带你到一个漂亮的花园，花园中央有一个喷泉。在这里，你可以享受几分钟的宁静时光。如果你还想继续走，走到花园的尽头，你会发现一座木楼梯，楼梯将带你下到港口。你可以从那里欣赏到船只的景色。沿水边还有一条步道，最终会将你带回到樱桃街。你可以看到，在这片城市区域，做的事情真的是不少。我们的巴士将在1:30离开。

第二部分到此结束。你现在有半分钟的时间检查你的答案。

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第三部分：

你将听到一位导师和两位学生讨论水稻这一作物。首先，你有一些时间来看问题 21 到 24。现在认真听并回答问题 21 到 24。

早上好，大家好。接着我们上周讨论的欧洲农业教程，今天戴西和埃里克将谈论亚洲最常种植的作物——水稻。

埃里克，你能告诉我们你们的研究进展吗？

是的，当然。我们一直在研究水稻在几个国家的作用，水稻的种植方式，以及提高产量的方法。正如你们所知道的，水稻是整个亚洲的主食，事实上，世界上90%的水稻都是在亚洲种植和食用的。戴西对此有一些背景介绍。

水稻最初是一种野生植物，起源于亚洲的热带地区。但今天，水稻已经有数百个品种，每个品种都有不同的特性。例如，有一种能耐受洪水，另一种则能在相对干燥的条件下生长。还有一种水稻具有非常香的气味。但无论它在哪里生长，水稻都需要大量的水。

你说的“大量”是什么意思？

嗯，种植一公斤水稻大约需要5000升水。这些水可以通过自然降水或者灌溉来提供。而且，由于大多数水稻种植国都面临不稳定的天气，包括干旱，因此水资源管理至关重要！

研究变得非常重要，以至于每个水稻种植国都有自己的水稻研究所，不管是日本、中国还是孟加拉国，而且这些研究所都由菲律宾的国际水稻研究所协调。

有意思。

以孟加拉为例，他们已经成功地使用了不同的水稻品种和肥料长达30年，但由于这个国家地势平坦、是三角洲地区，雨季过后水分很难排出，因此他们需要找到能耐受洪水的特殊水稻品种。随着全球变暖，情况变得比以往更紧迫。

在你听到后面的讨论之前，你有一些时间来看问题 25 到 30。

现在，我想进入我们的比较研究。正如你们可以想象的那样，中国是世界上最大的水稻生产国。全中国人民每天大概吃掉超过30亿碗米饭。相当惊人的数字。

嗯。

当然，水稻在中国文化中也扮演着重要角色。接下来我们对比一下中国和泰国。你知道，尽管泰国人口只有约6400万，它却是世界上最大的水稻出口国。不是中国，你可能会以为是中国。

是吗？

对。泰国将水稻销往世界各地，尤其是欧洲、非洲和中东。据说，泰国茉莉花米是世界上最贵的水稻品种，这也是泰国水稻出口业蒸蒸日上的原因之一。人们希望吃点不一样的东西。当然，泰国非常适合水稻种植，气候条件优越，水源充足。

如果稍微回到中国，我们应该提到，在黄州的水稻研究所，他们正在研究如何用更少的水来提高水稻的产量。

“产量”是什么意思呢？

就是他们能够种植的量？

对。他们在努力寻找用更少的土地种更多的水稻，改善水稻的味道，并且希望水稻中除了碳水化合物外还能有其他有益的成分，使它更健康，对人体更有益。

考虑到水稻是主食，这个主意不错。

然后是日本，在水稻方面完全自给自足。基本上是因为他们对进口米设有高额关税，所以大家都购买国产米，他们出口的水稻很少。

是的。你知道，尽管水稻在日本几乎是神圣的作物，但消费量仅为1960年代的一半。这个趋势在泰国或中国并不明显。

有趣的是你提到水稻在日本几乎是神圣的作物，因为我相信在泰国它也有重要的文化意义。

完全正确。泰国每年都有皇家播种仪式，国王总是亲自参与，并实际撒播新的水稻种子。

有趣。那么，农民们必须撒播新的种子，来自全国各地的农民都会聚集到曼谷参加这个活动。

关于全球对有机农业的关注，是否有机种植的水稻呢？

当然有，而且日本人对有机水稻的需求也越来越大。位于日本稻米生产带附近的秋田市有一家实验农场，闻名遐迩，生产有机水稻，现在这种水稻在全国销售。这有点像泰国茉莉花米的流行，但那主要是出口市场的需求。

有趣的是，人们对态度的变化越来越感兴趣，不是吗？

第三部分到此结束。

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第四部分：

你将听到一段关于昆虫生物学101课程的介绍。首先，你有一些时间来看问题 31 到 40。现在，认真听并回答问题 31 到 40。

下午好，欢迎来到昆虫生物学101课程。首先，我想谈谈昆虫对我们有益的一面。昆虫无处不在，既是我们的好朋友，也常常带来困扰，甚至有时会带来严重的危害。

首先，让我们谈谈昆虫为我们做的好事。可能对人类来说，最重要的昆虫，甚至对所有生物来说，都是蜜蜂。蜜蜂帮助植物进行授粉，因此对大多数花卉和结果植物来说，它们都是必不可少的。它们将花粉从雄花传递到雌花。如果没有蜜蜂，我们几乎没有什么食物植物，也没有水果。事实上，我们人类将无法生存。甚至像爱因斯坦这样的伟大思想家也曾指出，没有蜜蜂，人类在一年内将灭绝。我们将饿死。事情就是这么简单。这也许可以让我们变得谦虚一些。

稍微不那么戏剧性的是，蜜蜂还为我们制作蜂蜜。而且，它们生产的蜂蜡也可以用来做蜡烛，也可以用作一流的家具擦亮剂。当然，这些可能对我们的生活并非至关重要，但它们可以提醒我们蜜蜂的重要性。这是我在这门课程中不断强调的一个观点。虽然公平地说，我还得指出，蝴蝶在授粉方面也与蜜蜂一样起着重要作用。

现在，在密歇根州，夏天最糟糕的是什么？没错，就是蚊子。但我现在说的可是有益的昆虫，对吧？那么，让我们稍微谈一下蜻蜓。首先，如果没有蜻蜓，蚊子会更多。蜻蜓主要吃蚊子，也吃一些其他的昆虫。没错，它们可不仅仅在飞来飞去。它们还帮助消灭有害昆虫。所以，下次你看到蜻蜓时，可千万别杀了它。

接下来，我们聊聊那些有害的昆虫。拿蚊子来说吧，几年前，蚊子在美国不仅仅是令人讨厌，它们有时甚至致命。它们传播疟疾和黄热病。我的祖先，南方联盟将军约翰·贝尔·胡德，经历过美国内战中的最激烈战斗，但最终却死于黄热病，享年38岁。不是子弹，而是害虫。

那么，除了蚊子，夏天还有一种似乎永不疲倦的昆虫。没错，就是苍蝇。在我继续讲下去之前，我得提到一种非洲苍蝇——采采蝇，它吸食血液，可以给人和动物带来严重的疾病。此外，它仍然传播睡眠病，每年影响约30万人，治疗这种病只能使用毒性很大的药物，而这些药物很难服用。更糟糕的是，药物有时无效。

当然，还有其他昆虫破坏农作物。在中国，举个例子，蝗虫仍然是一些地区农业收成的威胁。虽然这些昆虫的危害较小，但它们依然令人厌烦。像蛀衣虫会吃人的衣物，尘螨会慢慢摧毁地毯。而更糟糕的是，白蚁（白蚁）会吃木头，也就是你家里的木材。如果它们得不到制止，最终可能会毁掉整个房子。通常，在人们察觉之前，它们已经给建筑物造成了严重的损害。所以，正如我们所知道的那样，昆虫有时真的是一大麻烦。那么该怎么办呢？

你可以开始杀掉有害昆虫了。在中国的共产主义革命后的几十年里，毛主席鼓励人民打死看到的每一只苍蝇。墙上的标语把它们称为“小资本家”。但苍蝇繁殖得太快了，这显然不是一个长期解决的办法。

在西方的几十年里，用化学药品杀死昆虫似乎是一个好办法。不幸的是，化学药品只能在有限的地区、有限的时间内使用。这是一个小范围的解决方案，昆虫总是会回来。更糟糕的是，像DDT这样的毒药被发现对环境有害。许多野生动物，如老鹰，都受到了影响。并且，在使用化学药品的农村地区，人们的肝癌发生率是全球最高的之一。显然，化学药品对人类是有害的。

像所有物种一样，昆虫对其环境的变化具有惊人的适应能力。当一种新的化学药品被引入到它们的栖息地时，那些能够抵抗有害效果的昆虫通常会生存下来。它们随后与其他幸存者交配，就这样，昆虫在几代之间变得对大多数毒药产生抗性。请记住，一代昆虫最多也就几个月。

所以，我们再次问该怎么办呢？

好吧，有一些生物解决方案。其中一些非常简单。一个方法是摧毁昆虫的栖息地。你把它们的家或食物拿走。打扫厨房是防止蟑螂的最好方法。没有垃圾，就没有食物。清除沼泽和湿地就能消除蚊子。其他解决方案可能包括在蚊子很多的地方引入蜻蜓或蝙蝠。这比化学药品便宜。像这样的方法不会对环境造成额外污染。但是你必须小心。如果你改变环境太多，你可能会意外地伤害到其他生命形式。

一个最近控制昆虫种群的方法是打断它们的繁殖周期。这是什么意思？这意味着昆虫的“节育”。昆虫被提供食物，使它们无法繁殖。由于它们无法生育，昆虫种群会消失，或者几乎消失。而且因为没有年轻的昆虫诞生，抗药性问题也不会出现，没有新的昆虫能产生增强的抗药性。打断生命周期，消除昆虫。

很显然，我们必须了解昆虫的生命周期。至少，这是计划的目标。随着课程的进展，我们将深入讨论这一点。

现在，我停下来看看大家是否有问题。

第四部分到此结束。你现在有半分钟的时间检查你的答案。