问题 解答题

如图所示,图是鸟卵的结构示意图,据此回答下列问答:

(1)填写图中各结构各称.

①______;②______;③______;

④______;⑤______;⑥______;

⑦______;⑧______.

(2)具有保护卵细胞作用的结构是______和______.

(3)进行胚胎发育的部位是______.

(4)为受精卵发育成胚胎提供营养的结构是______和卵白.

答案

如图鸟卵的结构:

可知:①卵壳膜②气室③卵壳④胚盘⑤卵黄膜⑥卵黄系带⑦卵黄⑧卵白,其中卵黄即鸟卵内部发黄的部分.鸟卵中的大多数蛋白质都集中在卵黄部分,其为胚胎发育提供营养.卵白可以为受精卵发育提供水分和部分营养; 减少震荡,其保护受精卵和缓冲的作用,所以为受精卵发育成胚胎提供营养的结构有卵黄和卵白.对卵细胞具有保护作用的有:卵壳、卵壳膜和卵白.卵黄上的小白点叫做胚盘,含有细胞核,内有遗传物质,是由受精卵分裂形成的.是进行胚胎发育的部位.

故答案为:(1)①卵壳膜②气室③卵壳④胚盘⑤卵黄膜⑥卵黄系带⑦卵黄⑧卵白

(2)卵壳、卵壳膜和卵白

(3)胚盘

(4)卵黄

阅读理解

阅读理解

     On a PC (个人电脑), having to fill out a form and type in a credit card number to buy something

is only mildly annoying. On a cellphone, it could make you want to skip the purchase entirely.

     This is why investors, startups (初创企业) and major corporations are pouring money into services

that make it easier to use cellphones to buy goods and transfer money. The aim is to turn phones into

virtual credit cards or checkbooks, enabling the kind of clickandbuy commerce and online banking that

people have come to expect on their PCs. But shrinking down (缩小) those services presents serious

challenges.

     The services must work on many different phones and through many cellphone service providers,

which usually control the billing relationships with customers. That adds complexity to the already tricky

business of safely and securely transferring funds among financial institutions and merchants.

     Mobile payment systems have been tried before, with only modest success. Driving a new flurry (一

阵兴奋) of deal making, industry analysts and executives say, is the success of the iPhone, BlackBerry

and other sophisticated (尖端的) devices. These phones make complex interactions easier.

     Now the race is on to develop new payment systems-and to get several percentage points in fees

from each transaction. They're seeing that returns could be so huge. Obopay, a startup that lets people

transmit money to one another via text message, raised $ 35 million from Nokia's investment. Also, a

mobile payments startup called Boku announced that it had received $ 13 million in venture capital

financing.

     When people can use their phone numbers to make a purchase, they are 10 times as likely to follow

through on a transaction as when they have to type in credit card and billing information, said David

Marcus, chief executive of a startup called Zong.

     Mobile payment companies also need to get cooperation from merchants, which must add a payment

option to their mobile sites or applications.

     But the potential opportunity to get fees from the growing number of mobile transactions is too__

juicy__to__pass__up,__despite the risks, said an analyst with IDC Financial Insights, a market research

company.

1. From the passage, we should face ________ great difficulties while purchasing through

    cellphones instead of PCs. 

A. one                

B. two

C. three                

D. four

2. According to the passage, using phones to make a purchase is ________.

A. expensive            

B. convenient

C. troublesome          

D. impossible

3. What does the underlined phrase "too juicy to pass up" in the last paragraph probably mean?

A. Too profitable to ignore.                            

B. Too difficult to seize.

C. Too heavy to lift.                                    

D. Too unsafe to handle.

4. What would be the best title for the passage? 

A. The Benefit of Purchasing via Cellphone

B. The Great Risks on Payments via Cellphone

C. How to Deal with Payments via Cellphone

D. Investors Bet on Payments via Cellphone

判断题