高中英语人教大纲第三册：Unit4 Green world(第四课时).doc

The Fourth PeriodTeaching Aims:1.Get the students to grasp the main idea of the text so as to improve their reading ability.2.Get the students to learn the scientific way for the scientists to do their research workthe way to think and observe.3.Get the students to write a description of plants.Teaching Important Points:1.How to analyse an article so as to grasp its main idea.2.How to write a description according to the information given.Teaching Difficult Point:How to improve the students reading abilityhow to analyse an article.Teaching Methods:1.Pair work or group work to make every student take an active part in the class.2.Discussion to get the students to understand what they are learning better.Teaching Aids:1.a computer2.a courseware3.a tape recorderTeaching Procedures:Step Greetings and RevisionGreet the whole class as usual.T:In the last period,you were told to make sentences with the useful words and expressions in the text.Have you got prepared?(Ss:Yes.)Now read the sentences to us.Volunteer!One student,one sentence.Sa:make attempt to do sth.They made no attempt to escape.(at escaping)Sb:classifyThe books in our school library are classified according to subject.Sc:groupGroup together in two!S D:identificationHe carries identification with him at all times when he is out.S E:promoteHe works to promote the friendship between the two countries.S F:privilegeThey fight against privilege in order to create a fairer society.SG:cosyHe lives in a nice cosy little house.SH:have an appetite forThe enemy had no appetite for the fight.S I:appointHe was appointed minister to a foreign country.S J:calculateThe scientists calculated when the spaceship would reach the moon with a calculator.S K:on a large scaleThe work of reforming industry carried out in all provinces on a large scale.S L:involveThe case involved several leaders.Sm:accumulateHe accumulated a fortune by investing wisely.Sn:abandonHe found a baby abandoned by his parents.Step Preparation for ReadingT:So much for homework.Now open your books and turn to Page 169.Lets read the new words and expressions of this period.Who will read them to us?Sa:Ill try.(Teacher asks some students to read the new words and expressions.While reading,let other students correct the mistakes made by the students.Then play the tape to get the students to follow.Teacher may give brief explanation about their usages when necessary.)Step Fast-readingT:Youve learnt something about Carl Linnaeus,Daniel Solander and Joseph Banks in the text weve just studied.And youve read about Michurin and Darwin.Today,well learn about another two scientists Gregor Mendel and Gote Turesson.What did they do?What contribution did they make?After weve learnt the passage,Ill sure youll have a clear idea.(Show the following on the screen.)Now read the text fast and try to grasp the main idea of the text as much as possible.Then find answers to the questions on the screen.Answer the following questions:1.What was Charles Darwins hobby when he was young?2.What led Darwin to write his famous book “On the Origin of Species”?3.Who founded the science of genetics?4.Who made contribution to the improvement of the output of crops according to the text? (Students begin to read the text.After a few minutes,teacher says the following.)T:Have you finished?Ss:Yes,we have.T:Now give us the answers,please.One student,one question.Sb:1.When he was young,Darwin enjoyed doing all kinds of experiments and studying physics,chemistry and later botany was his hobby.Sc:2.When he was twenty-two years old,he was invited to take part in the scientific expedition on the Beagle.His observation on the five-year voyage led him to write his famous book.On the Origin of Species.S d:It was the research work of Mendel that gave birth to the science of genetics.S e:Mendels genetics and Turessons findings are both important to the output of crops.T:What you said is right.Thank you for giving us such good answers.Step Reading and ComprehensionT:(Show the following on the screen.)Now lets read the text again and discuss the questions on the screen.Pair work or group work.1.The research of Charles Darwin,Gregor Mendel and Gote Turesson is like pieces in a puzzle that show a complete picture when put together.(1)What did Darwin discover about bird species in Galapagos?(2)What did Mendel observe in his experiments with peas?(3)Looking at wild plant species in Sweden,what did Turesson discover?2.Complete the following sentence.Darwins discoveries in Galapagos were based on differences_wild species,while Turessons observations showed that there are stable varieties _wild species.3.That soil conditions are important to the output of crops was known more than 2000 years ago.Why are Turessons discoveries still important to agriculture then? (Teacher goes among the students and joins the students in their discussion.)T:(After some minutes discussion.)Now give us your answers,please.Who will answer the first question?Sf:He found 13 kinds of findes,related to each other in the structure of their beaks,tails,shape of body and colour of their feathers.The most curious fact was the differences in the size of the beaks.This could only be explained from the differences in habitat and source of food.The birds with broad beaks would eat hard seeds,while the birds with smaller beaks would eat soft seeds or insects.T:Please give us the answers to the second question.Sg:He found that many characteristics were passed on from one generation to the next,without influence by the environment.Sh:Ill answer the last question of Part 1.He found evidence for the existence of stable varieties within species in nature.He showed that differences between plants of one species occurred as a result of the environmental conditions in their habitat.Si:I think,in Part 2,for the first blank,we should fill in the words “of different” and the second,“of the same”.Am I right?T:What do you think,S j?SJ:I think he is right.T:For the last question,what are your opinions?Sk:Soil conditions are important to the output of crops.But that is one side of the question.The research by Darwin,Mendal and Turesson shows that both genetics and the environment are important to plants.If we dont have good seeds,good soil conditions are not enough for us to improve the output of the crops.Am I right?Ss:We agree with you.(Teacher plays the tape after the students discussion.Then teacher asks students to read the text aloud and find questions in the text.Teacher gives brief explanation to them.)Step Summary and HomeworkT:Now lets think about a question:What can we learn from the text?(Write it on the blackboard.)Discuss it with your partner.(After a while.)Who can tell us what you think?S1:We should observe everything carefully and think deeply,then we can draw a good conclusion.T:Very good.Now lets see how the scientists observe and think.(Teacher writes Observation,Thinking,Conclusion.on the Bb.)T:So much for the text.Now todays homework:1.Make sentences with the words and phrases:whatever;lead sb. to do sth.;nowhere,variety;in view2.Do Writing on Page 35.Sample writing:DandelionsIn nature,there are varieties of environmental conditions for the plants to grow in.Some places are hot and dry and there is little rain while in other places it is cool and wet.So the same plants that grow in different places are quite different.Lets take dandelions as an example.They are widespread and can be found almost everywhere.Their yellow flowers are beautiful and their leaves look like the teeth on a saw.The wind spread their flowers and seeds everywhere,so when they grow in hot and dry places,they are low and thin.Their flowers and leaves are short and light in colour,5-10 cent