问题 选择题

科学家通过研究发现,有一种果蝇的基因发生突变(一种变异)后,在210C的气温下生活能力很差,当气温升高到250C时其生活能力大大提高了.这一现象说明(  )

A.温度高低是决定果蝇变异的主要因素

B.变异个体适应环境的能力大大提高了

C.变异的有利与不利取决于生物生存的环境条件

D.生物变异大多是有利的

答案

遗传是指亲子间的相似性,变异是指亲子间和子代个体间的差异.按照变异对生物是否有利分为有利变异和不利变异.有利变异对生物生存是有利的,不利变异对生物生存是不利的.生物与环境相适应,环境不断变化,因此生物只有不断变异,才能适应不断变化的环境.有的变异对生物个体本身有利,有利于个体生存的变异是有利变异;对个体生存不利的变异是不利变异.种果蝇的基因发生突变后,产生的变异在21℃的气温下生活能力很差,表明该变异不适于此环境,是不利变异;在气温升高到25℃,其生活能力大大提高了,表明该变异适于25度的环境,在25度的环境中是有利变异.因此变异的有利、有害完全取决于环境条件,适应环境的变异是有利变异.

故选:C.

阅读理解

Four men who would become fathers were in a hospital waiting room while their wives were in labor (分娩). The nurse arrived and proudly said to the first man, “Congratulations, sir. You’re the father of twins!”

“What a coincidence (巧合)! I work for the Minnesota Twins Baseball teams!”

Later the nurse returned and congratulated the second father on the birth of his triplets (三胞胎).

“Wow! That’s unbelievable! I work for the 3M Company.”

An hour later, the nurse returned to congratulate the third man on the birth of his quadruplets (四胞胎). Surprised, he only could answer, “I don’t believe it! I work for the Four Seasons Hotel!”

  After this, everyone turned to the fourth man who had just fainted (晕). The nurse ran fast to his side. As he slowly came to himself, they could hear him speak in a very low voice over and over, “I should never have taken that job at 7-Eleven. I should never have taken that job at 7-Eleven. I should never have taken that job at 7-Eleven.”

小题1:Why were the fathers there?

A.They were waiting for their wives.  

B.They were seeing doctors.

C.They were waiting for their babies to be born.  

D.They were working at men nurses there.小题2:Which of the following is true about the third man?

A.He thought the nurse made a mistake. 

B.He was very surprised at the nurse’s words.

C.He didn’t want to have these babies.  

D.He should never have worked at 7-Eleven.小题3:Why did the fourth man faint when he heard what the nurse told the third man?

A.Hew was afraid of having so many babies.  

B.He was seriously ill.

C.He was too excited.

D.He was very glad to have 7 babies.小题4:At least how many babies would be born according to the story?

A.9.

B.10.

C.11.

D.16.

选择题