问题 解答题

大蒜被人们誉为天然“抗生素”.大蒜真的能抑制细菌的生长吗?甲、乙两位同学进行了如图所示两个实验.实验前先将金黄色葡萄球菌均匀地接种在培养皿的营养琼脂上.

根据上述实验,回答下列问题:

(1)圆纸片周围的清晰区为无菌区,本实验得到的结论是______.

(2)你认为哪位同学设计的方案合理并简述理由.______.

答案

(1)由题意可知,该实验是探究大蒜能抑制金黄色葡萄球菌的生长.实验变量是大蒜,浸有大蒜液的圆纸片为实验组,浸有无菌水的圆纸片为对照组,37℃是模拟人体的体温,培养24小时后,若浸有大蒜液的圆纸片的周围金黄色葡萄球菌的菌落明显小于浸有无菌水的圆纸片周围的菌落,则本实验得到的结论是大蒜能抑制金黄色葡萄球菌的生长;若浸有大蒜液的圆纸片的周围金黄色葡萄球菌的菌落不小于浸有无菌水的圆纸片的周围的菌落,则说明大蒜不能抑制金黄色葡萄球菌的生长.

(2)设置对照实验,可以保证除了所研究的因素不同之外,其他因素都相同.这样实验结果的不同只能是由变量引起的.使实验结果具有说服力.甲同学的实验没有对照组,乙同学的实验设置了对照组,因此,乙同学设计的方案合理

故答案为:(1)大蒜能抑制金黄色葡萄球菌的生长或大蒜能抑制葡萄球菌的生长;

(2)乙同学,设置了对照组.

单项选择题
单项选择题

No revolutions in technology have as visibly marked the human condition as those in transport. Moving goods and people, they have opened continents, transformed living standards, spread diseases, fashions and folk around the world. Yet technologies to transport ideas and information across long distances have arguably achieved even more they have spread knowledge, the basis of economic growth.
The most basic of all these, the written word, was already ancient by 1000. By then China had, in basic form, the printing press, using carved woodblocks. But the key to its future, movable metal type, was four centuries away. The Chinese were hampered by their thousands of ideograms. Even so, they quite soon invented the primitive movable type, made of clay, and by the 13th century they had the movable wooden type. But the real secret was the use of an easily cast metal.
When it came, Europe-aided by simple Western alphabets-leapt forward with it. One reason why Asia’s civilizations, in 1000 far ahead of Europe’s, then fell behind was that they lacked the technology to reproduce and diffuse ideas. On Johannes Gutenberg’s invention in the 1440s were built not just the Reformation and the Enlightenment, but Europe’s agricultural and industrial revolutions too.
Yet information technology on its own would not have got far. Literally: better transport technology too was needed. That was not lacking, but here the big change came much later: it was railways and steamships that first allowed the speedy, widespread dissemination of news and ideas over long distances. And both technologies in turn required people and organizations to develop their use. They got them: for individual communication, the postal service; for wider publics, the publishing industry.
Throughout the 19th century, the postal service formed the bedrock of national and international communications. Crucial to its growth had been the introduction of the stamp, combined with a low price, and payment by the sender. Britain put all three of these ideas into effect in 1840.
By then, the world’s mail was taking off. It changed the world. Merchants in America’s eastern cities used it to gather information, enraging far-off cotton growers and farmers, who found that New Yorkers knew more about crop prices than they did. In the American debate about slavery, it offered abolitionists a low-cost way to spread their views, just as later technologies have cut the cost and widened the scope of political lobbying. The post helped too to integrate the American nation, tying the newly opened west to the settled east.
Everywhere, its development drove and was driven by those of transport. In Britain, travelers rode by mail coach to posting inns. In America, the post subsidized road-building. Indeed, argues Dan Schiller, a professor of communications at the University of California, it was the connection between the post, transport and national integration that ensured that the mail remained a public enterprise even in the United States, its first and only government-ran communications medium, and until at least the 1870s, the biggest organization in the land.
The change has not only been one of speed and distance, though, but of audience. About 200 years ago, a man’s words could reach no further than his voice, not just in range but in whom they reached. But, for some purposes, efficient communication is mass communication, regular, cheap, quick and reliable. When it became possible, it transformed the world.

Which of the following statements is NOT true about the postal service

A.American abortionists were not happy about it.

B.The stamp was invented in Britain.

C.It helped the independence of America.

D.In the 1840s it was the major means of national communications in Britain.