1甲壳虫
This morning I want to tell you about a recent scientific discovery dealing with the relationship between plants and animals. This is about a desert shrub whose leaves can shoot a stream of poisonous resin a distance of six feet. You think it would be safe from all attacks by insects? But a recent study has found one insect, a beetle that can chew its way past the plant's defense system by cutting the main vein that delivers the poison to the leaves. This vein cutting is just one method the beetles used to prepare a safe meal. Another is by cutting a path all the way across the leaves to hold the flow of chemicals. Then they simply eat between the veins of poison. In the past, scientists who studied insect adaptation to plant defenses have focused on chemical responses, that is, how the insects can neutralize or alter the poisonous substances plants produce. What's unique about this chewing strategy is that the beetle is actually exhibiting a behavioral response to the plant's defenses rather than the more common chemical response. It is only after a beetle's survived several encounters with the plant's resin that it learns how to avoid the poison: by chewing through the resin transporting veins on the next leaf it eats, and thus gives itself a
safe meal. However, it can take a beetle an hour and a half of careful vein cutting to prepare a small leaf that takes it only a few minutes to eat. So, though the method is effective, it's not very efficient.
生词摘录：
1. shrub: n. 灌木
2. resin: n. 树脂
3. beetle: n. 甲壳虫
4. vein: n. 静脉
5. neutralize: v. 中和
6. alter: v. 改变
7. defense system：防御系统
strategy: 策略 方法
2非洲小草鼠
Human populations near the equator have evolved dark skin over many generations because of exposure to the fiercest rays of the sun. A similar phenomenon has also occurred in other parts of the animal kingdom. The African grass mouse is a good example. Most mice are nocturnal, but the African grass mouse is active during daylight hours. This means that it spends its days searching for food in the semi-dry bush in scrubby habitats of eastern and southern Africa. Its furry stripe's like a chipmunk's, which helps it blend in with its environment. Because it spends a lot of time in the intense tropical sun, the grass mouse has also evolved two separate safeguards against the sun's ultraviolet radiation. First, like the population of humans in this region of the world, the skin of the grass mouse contains lots of melanin, or dark pigment. Second and quite unusual, this mouse has a layer of melanin-pigmented tissue between its skull and skin. This unique cap provides an extra measure of protection for the grass mouse and three ot
her types of African mouse, like rodents that are active during the day. The only other species scientists has identified with the same sort of skull adaptation is the white tent-making bat of the Central American tropics. Although these bats sleep during the day, they do so curled up with their heads exposed to the sun.
生词摘录：
1. Fiercest： adj 残忍的 猛烈的
2. scrubby: adj. 树丛繁盛的
3. stripe: n. 条纹
4. ultraviolet radiation: adj. 紫外线
5. melanin: n. 黑素
6. rodent: n. steele啮齿类动物
7. blend: v. 混合
3恐惧
We've been looking at fear from a biological perspective, and someone asked whether the tendency to be fearful is genetic. What some studies done with mice indicate that mammals do inherit fearfulness to some degree. In one study, for instance, a group of mice was placed in a brightly lit open box with no hiding places. Some of the mice wandered around the box and didn't appear to be bothered about being so exposed. But other mice didn't move. They stayed up against one wall which indicated that they were afraid. Well, when fearful mice, or you might say anxious mice like the ones who stayed in one place, when mice like these were bred with one another repeatedly, after about twelve or so generations, then all of the offspring showed similar signs of fearfulness. And even when a new born mouse from this generation was raised by a mother and with other mice who were not fearful, that mouse still tended to be fearful as an adult. Now why is this? Well it's thought that specific genes in an animal's body have an influence on anxious behavior. These are genes that are associated with particular nerve-cell receptors in the brain. And the degree of overall of fearfulness in the mammal seems to d
epend in large part on the presence or absence of these nerve-cell receptors. And this appears to apply to humans as well by the way. But while a tendency towards anxiety and fear may well be an inherited trait, the specific form that the fear takes has more to do with the individual's environment. So a particular fear, like the fear of snakes or the fear of spider, say, is not genetic, but the overall tendency to have fearful responses, is.
生词摘录：
1. genetic: adj. 遗传的
2. offspring: n. 子孙，后代
3. receptor: n. 接受器
4. inherit: vt.继承
5. be bred with: 与....交配
4广告
Let's turn our focus now to advertising. We all know what an advertisement is. It's essentially a message that announces something for sale. Now there's an important precondition that must exist before you have advertising, and that's a large supply of consumer goods, that is, things to sell. You see in a place where the demand for a product is greater than the supply, there is no need to advertise. Now the earliest forms of advertising going back many hundreds of years with a simple sign over shop doors that told you whether the shop was a bakery, a butcher shop or what have you. Then with the advent of printing press, advertising increased substantially. Ads for products like coffee, tea and chocolate appeared in newspapers and other periodicals, as well as on the sides of building. In the American colonies, advertising and communications media like newspapers and pamphlets became a major factor in marketing goods and services. By modern standards, these early advertisements were quite small and subdued, not as splashy, whole page spread of today. Still some of them appeared on the front pages of newspapers probably because the news often consisted of less refresh reports from distant Europe while the ads were current and local. Advertising really came and do it so
and became an essential part of doing business during the industrial revolution. Suddenly there was a much greater supply of things to sell. And as we said earlier, that is the driving force behind advertising. People's attention had to be drawn to the new product. Let's take a look at some of the advertisements from that time. 
生词摘录：
1. essentially: adv. 本质上，本来
2. precondition: n. 先决条件
3. bakery: n. 面包店
4. butcher: n. 屠户
5. periodical: n. 期刊
6. pamphlet: n. 小册子
7. subdued: adj. 被抑制的
8. splashy: adj. 大而显眼的，引人注目的
5杂志
Moving away from newspapers, let's now focus on magazines. Now, the first magazine was a little periodical called The Review, and it was started in London in 1704. It looked a lot like the newspapers of the time. But in terms of its content, it was much different. Newspapers were concerned mainly with news events, but The Review focused on important domestic issues of the day as well as the policies of the government. Now in England at the time, people could still be thrown in jail for publishing articles that were critical of the king. And that's what happened to Daniel Defoe. He was the outspoken founder of The Review. Defoe actually wrote the first issue of The Review from prison. You see, he had been arrested because of his writings that criticized the policies of the Church of England, which was headed by the king. After his release, Defoe continued to produce The Review and magazine started to appear on a more frequent schedule, about three times a week, it didn't take long for other magazines to start popping up. In 1709, a
magazine called The Tatler began publication. This new magazine contained a mixture of news, poetry, political analysis, and philosophical essays. 

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