【正文】 f the book is Origin of Species.　　3. Thomas Newen, British (16631729), an inventor of steam engine.　　4. Gregor Mendel, Czech, a botanist and geneticist.　　5. Marie Curie, Polish and French, a chemist and physicist.　　6. Thomas Edison, American, an inventor.　　7. Leonardo da Vinci, Italian, an artist.　　8. Sir Humphry Davy, British, an inventor and chemist.　　9. Zhang Heng, ancient China, an inventor.　　10. Stepper Hawking, British, a physicist.　　Step Ⅲ Prereading　　Get the students to discuss the questions on page 1 with their partners. Then ask the students to report their work. Encourage the students to express their different opinions.　　T: Now, class, please look at the slide. Discuss these questions with your partners. Then I’ll ask some students to report their work.　　Show the following on the screen.　　What do you know about infectious diseases?　　What do you know about cholera?　　Do you know how to prove a new idea in scientific research?　　What order would you put the seven in? Just guess.　　Sample answer 1:　　S1: Let me try. Infectious diseases can be spread easily. They have an unknown cause and may do great harm to people.　　S2: People could be exposed to infectious diseases, so may animals, such as bird flu.　　S3: AIDS, SARS are infectious diseases.　　S4: Infectious diseases are difficult to cure.　　Sample answer 2:　　S1: Cholera is caused by a bacterium called Varian cholera.　　S2: It infects people’s intestines, causing diarrhea, vomiting and leg cramps.　　S3: The most mon cause of cholera is people eat food or drink water that has been contaminated by the bacteria.　　S4: Cholera can be mild or even without symptoms, but a severe case can lead to death without immediate treatment.　　Sample answer 3:　　S1: I know sth. about it. First we should find the problem. Then, think of a solution.　　S2: We should collect as much information as possible.　　S3: Analyzing results is the most important stage.　　S4: Before we make a conclusion, it is necessary for us to repeat some stages or processes.　　Sample answer 4:　　S1: I think “Find a problem” should be the first stage.　　S2: “Make up a question” should follow the first stage.　　S3: “Think of a method”, “Collect results” and “Analyze results” are after that.　　S4: Of course, before “Make a conclusion”, we should “Repeat if necessary”.　　T: Well done! When we want to solve some problems, first we should find out the problem, do some research on it, prove your findings, and then make a conclusion. This is a scientific and objective way of researching. Now let’s see how doctor John Snow did his research.　　Step Ⅳ Reading　　Let the students skim the whole passage and try to work out the meanings of the new words and structures using context.　　T: The effect of cholera in the nineteenth century London was devastating. Many people died without knowing the reason. It was doctor John Snow who saved the people. Please look at the screen. Let’s read the whole passage and find answers to the questions.　　Show the questions on the screen.　　1. What conditions allowed cholera develop?　　2. Why do you think people believed that cholera multiplied in the air without reason?　　3. What evidence did John Snow gather to convince people that idea 2 was right?　　Sample answers:　　S1: The dirty water made the cholera develop quickly.　　S2: Because people could not understand its cause and could not get it cured. So people imagined that some poisonous gas i