高中英语外研版 (2019)选择性必修 第二册Unit 5 A delicate world授课ppt课件

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Unit 5A delicate wrld
T learn the use f “it” as an empty bjectT learn t describe the changes using “it” as an empty bjectT learn smething abut ecsystems
Read the fllwing sentences and g ver the use f it as an empty subject.
It is surprising that he is at the meeting.
It is a pity that yu didn't cme t the sprts meeting.
It seems that he kept calm befre danger.
It is useful fr us t learn t drive.
It is flish f yu t say that.
Lk at the sentences and answer the questins. Sentences (a) and (c) are frm the reading passage.
a N visitr wuld think it surprising that the island is a UNESCO Wrld Heritage Site.b N visitr wuld think that the island being a UNESCO Wrld Heritage Site is surprising.c Experts felt it necessary t cme up with a plan t remve all the rabbits frm the island.d Experts felt t cme up with a plan t remve all the rabbits frm the island was necessary.
1. What des “it” refer t in sentences (a) and (c)?
a N visitr wuld think it surprising that the island is a UNESCO Wrld Heritage Site.c Experts felt it necessary t cme up with a plan t remve all the rabbits frm the island.
It refers t that clause in sentence (a) and an infinitive in sentence (c).
2. What is the difference between the sentences in each grup?
When the bject f a sentence is a that-clause (b) r an infinitive (d), we smetimes use “it” as an empty bject and put the real bject later t keep balance. Fr example, sentence (a) uses “it” as the empty bject f “think”, referring t the real bject: “the island is a UNESCO Wrld Heritage Site”. Sentence (b) uses that-clause as the bject f “think”.
Nw lk fr mre sentences with this structure in the reading passage, and summarise its use in yur wn wrds.
This incident made it clear that the rat, muse and rabbit prblem needed slving nce and fr all.
…but we humans we it t the island t give it a happy ending.
it 作形式宾语的常见情况归纳如下：
1. it代替不定式短语。常用于：think/ find/ feel/ cnsider/ make/ regard... it + adj./n. + t d
I find it pleasant t wrk with him.They felt it difficult t finish the wrk in such a shrt time.She thinks it her duty t help him.All these nises made it impssible fr me t g n with the wrk.
2. it代替v.-ing只限于少数句型。 cnsider/think/find... it + gd/ use/ wrthwhile... + ding...
The prfessr cnsiders it n gd reading withut understanding.D yu cnsider it any use arguing with him?I dn’t think it wrthwhile ging t such a place.
3. it代替宾语从句(that有时候可以省略)。 think/find/make... it + n./adj. + Object Clause...
We all thught it a pity that the cnference was cancelled.They kept it quiet that he was dead.He hasn’t make it clear when he is cming back.
it 作形式宾语还有几种特殊情况，归纳如下：动词+ it + that从句，常见于put, have, take等动词后。例如： I take it that he will finish the task by himself.动词+ it + when/if从句，常见于appreciate, enjy, like, prefer等动词之后。例如： We really appreciate it if yu culd d us a favur.
动词 + it +介词短语 + that从句，常见于we it t sb, take it fr granted等结构中。例如： We we it t yu that we are still alive. I tk it fr granted that they were nt cming.动词+介词+ it + that从句，常见于lk t, depend n, insist n, stick t, answer fr等结构中。例如： She insisted n it that she was inncent. Yu may depend n it that he will help yu.
动词+ it +过去分词+从句。例如： He made it knwn t everyne that he was right. They haven’t made it knwn where they are t hld the cnference.
Rewrite the underlined parts using it as an empty bject.
Due t its cute appearance, many peple think keeping this turtle as a pet is a gd idea.
… many peple think it a gd idea t keep this turtle as a pet.
... and sme wners believe t release them int the wild is n big issue.
These days, peple have fund t release these turtles int the wild is a threat t ther species.
peple have fund it a threat t ther species t release these turtles int the wild
Experts cnsider wners keeping their pets in an enclsed area imprtant,
Lk at pictures f Saihanba Natinal Frest Park and find ut the changes.
present day
Lcated in Chengde City, Hebei Prvince, Saihanba (塞罕坝) sits 450 kilmeters t the nrth f Beijing. The place is cvered with snw seven mnths a year. It used t be a freezing, barren desert plagued by sandstrms. Hwever, it has been turned int the wrld’s largest human-made frest that cvers an area f nearly 75,000 hectares. Thus, it is called a “green miracle.”
Lk at the pictures f the Saihanba Natinal Frest Park and describe its changes using it as an empty bject where apprpriate. Yu may refer t the wrds and expressins in the table fr help.
I think it a breakthrugh t transfrm a desert int a frest...
I think it impssible t grw trees there in the 1960s.
I think it unrealistic t plant trees in the desert when the wrkers first came t Saihanba.
Describe hw a place yu knw has changed using it as an empty bject where apprpriate.
What makes the ecsystem balance?
Ecsystem means all the animals and plants in a particular area, and the way in which they are related t each ther and t their envirnment.
Prducer…, primary cnsumers…, secndary cnsumers…, decmpsers…
1. Prducers absrb water and disslved nutrients frm the sil.
absrb v. t take smething in, especially gradually 吸收
eg In cld climates, huses need t have walls that will absrb heat.
disslve v. t mix with sth., r t becme a part f sth. （使）溶解
eg Drp tw tablets int a glass f water and leave them t disslve.
2. Secndary cnsumers prey n primary cnsumers as well as eating ther animal matter.
prey n: (f an animal r a bird) t hunt and kill anther animal fr fd 捕食
eg Tigers prey n animals like rabbits.
3. Decmpsers break dwn dead animal and vegetable matter int nutrients.
break dwn: t make a substance separate int parts r change int a different frm in a chemical prcess 分解
eg Sugar and starch (淀粉) are brken dwn in the stmach.
【拓展】break dwn (会谈)破裂; 失败; (汽车等)出故障; (人的健康状况)变得恶劣
【归纳】break in 闯入; 打岔break ff 中断; 折断break int 闯入break ut 爆发; 发生break up 驱散; 分散; 打碎; 终止break thrugh 突围; 突破break away (frm) 挣脱(束缚); 脱离
【语境应用】用break短语的适当形式填空1) The wrms’ ability t _____________(分解) their everyday fd als allws them t break dwn plastic.2) The thieves _________________ and stle sme mney. 3) If he carries n wrking like this, he’ll _____________ sner r later.4) The American suthern states wanted t _______________ the Unin.5) Scientists think they are beginning t _____________ in the fight against cancer. 6) Their marriage _____________. 7) I was still living in Lndn when the war ____________.
break away frm
brke int the ffice
break thrugh
has brken up
4. The disslved chemicals are then released back int the fd chain, t be used by prducers.
release v. t let sb./sth. cme ut f a place where they have been kept r trapped 释放
eg Firefighters tk tw hurs t release the driver frm the burning car.
Lk at the diagram and answer the questins. Pay attentin t the wrds and expressins in bld.
1. What des the diagram shw?
The diagram shws a fd chain — the cnnectin between the living things.
2. What are the relatinships between the living things?
The living things are clsely cnnected with each ther by the fd they eat. Secndary cnsumers prey n primary cnsumers, primary cnsumers feed n prducers, and prducers absrb light frm the sun, and water and disslved nutrients frm the sil, which are prvided by decmpsers.
Cmplete the passage with the crrect frm f the wrds and expressins in Activity 5.
In a wdland ecsystem, trees and ther plants are prducers. They 1_______ water, take in nutrients frm the sil, and energy frm the sun. Insects are an example f a primary cnsumer. They 2_________ the prducers t prvide fd fr them, and are 3_________ by secndary cnsumers: small mammals and birds.
They 4________ the primary cnsumers. Wrms, fungi and bacteria are decmpsers. They 5___________ animal waste and the remains f living things. The chemicals these decmpsers 6__________ fertilise the sil and give the plants the nutrients they need t grw.