问题 解答题

某生物小组利用银边天竺葵(叶片边缘部分的细胞中无叶绿体,呈白色)进行了如下实验:

①将银边天竺葵放在黑暗处一昼夜.

②用不透光的黑纸片从上下两面遮盖在图中C处;用装有固体氢氧化钠(氢氧化钠可以吸收二氧化碳)的透明塑料袋将部分枝叶密封.把天竺葵放在光下照射几小时后,摘下叶片M、N,去掉遮光的黑纸片.

③将叶片M、N放入装有某溶液的烧杯里,隔水加热,脱去叶片中的叶绿素.

④把经过脱色的叶片放入清水中漂洗.

⑤将漂洗后的叶片放在培养皿里,滴加碘液,观察叶片颜色变化.

请分析回答:

(1)实验前将植株放到黑暗环境中的目的是______.

(2)实验中用于脱色的某溶液是______.

(3)滴加碘液后,发现只有B处变成蓝色,A、C、D处均未变蓝色.则

比较A、B两处,可以说明______.

比较B、C两处,可以说明______.

比较B、D两处,可以说明______.

(4)在整个实验过程中,银边天竺葵的细胞内始终进行的生理过程是______,该过程的反应式可以表示为

______.

(5)在光下放置数小时后,发现塑料袋的内壁上有小水珠,产生这一现象的原因是______.

答案

由题意可知:

(1)暗处理,实验前将植株放到黑暗环境中的目的:是消耗掉叶片原有淀粉,排除干扰,防止影响实验.

(2)脱色,使叶片含有的叶绿素溶解到酒精中,叶片变成黄白色,排除颜色的干扰.

(3)①由图可知:A、B两处的对照实验,变量是否有叶绿体,滴加碘液后,B处含有叶绿体变成蓝色,A处非绿色部分不含有叶绿体未变蓝色,说明叶绿体是进行光合作用的场所能.

②由图可知:B、C两处的对照实验,变量是否有光照,滴加碘液后,B处有光照部分变成蓝色,C处无光照部分未变蓝色,说明光是进行光合作用的条件.

③由图可知:B、D两处对照实验,变量是否有二氧化碳,滴加碘液后,B处含有二氧化碳变成蓝色,由于氢氧化钠可以吸收二氧化碳,D处的二氧化碳被氢氧化钠吸收了(不含有二氧化碳)未变蓝色,说明二氧化碳是进行光合作用的原料.

(4)呼吸作用是植物细胞利用氧,将有机物分解成二氧化碳和水,并且将储存在有机物中的能量释放出来.呼吸作用在所有的活细胞,有光无光都能进行.在整个实验过程中,银边天竺葵的细胞内始终进行的生理过程是呼吸作用,该过程的反应式可以表示为:有机物十氧→二氧化碳+水+能量.

(5)水分以气体状态通过叶片表皮上的气孔从植物体内散失到植物体外的过程叫做蒸腾作用;在白天,植物除进行光合作用、呼吸作用外还进行蒸腾作用;因此实验进行一段时间后通过蒸腾作用散失的水蒸气会在塑料袋的内壁上凝结成小水珠.

故答案为:(1)消耗掉叶片原有淀粉     

(2)酒精

(3)叶绿体是进行光合作用的场所    光是进行光合作用的条件

二氧化碳是光合作用的原料  

(4)呼吸作用    有机物+氧气→二氧化碳+水+能量

(5)天竺葵通过蒸腾作用散失的水蒸气会在塑料袋的内壁上凝结成小水珠

阅读理解
阅读理解。
                                                          
      Mrs Green was walking along a San Francisco street. Suddenly a man took her purse and ran. Mrs.
Green was very angry. She had ten dollars, her bus pass, and the keys to her house in her purse. Mrs.
Green ran after the thief. The thief ran one block (街区), two blocks, three blocks.
      The thief was a young man, so he could run fast. Mrs. Green was not a young woman - she was
73 years old - but she could run fast, too. Mrs. Green stayed right behind the thief. Mrs. Green was
wearing two chopsticks in her hair. The chopsticks had sharp (尖的) ends.
      Mrs. Green took the chopsticks out of her hair. "Maybe I can stab (刺,戳) the thief with these
chopsticks," she thought. "Then he will drop my purse." 
      The thief ran into a building. Mrs. Green followed him. "Help! Stop him!" she shouted. "He has my
purse!" Two police officers were walking near the building. They heard Mrs. Green and ran to help her.
One police officer stayed with Mrs. Green. The other police officer ran after the thief.
       The police officer found the thief at the corner of the building. The thief was looking in Mrs. Green's
purse. When he saw the police officer, the thief dropped the purse and ran away.
       A few minutes later the police officer caught the thief. He was found under a car and taken to jail
(监狱). The thief will stay in jail for a long time. But the thief was lucky. He was lucky that the police
caught him! Why?
1. What did the thief take from the woman?
[ ]
A. Ten dollars
B. Keys
C. A purse
D. A bus pass
2. Where did the thief hide?
[ ]
A. In the building.
B. Under a car.
C. In jail.
D. At the corner of the street.
3. A few ___________ later, the police caught the thief.
[ ]
A. minutes
B. hours
C. days
D. weeks
4. What is the best title of the story?
[ ]
A. A Lucky Thief
B. Two Police Officers
C. A Clever Granny
D. A Pair of Useful Chopsticks
选择题