问题 填空题

根据所学生物学知识回答问题:

(1)在测定种子的成分实验中,将少许小麦面粉用纱布包起来在水中不断揉挤,外边清水变为乳白色,乳白色水中含有的物质是______,可用______试剂检测;反复揉挤后纱布内剩下黄白色胶黏物质主要是______,可用_______试剂检测;植物种子长时间高温烘烤后会留下灰白色的灰烬,这说明种子中含有______,除以上所述物质以外,种子中含有的其余两种成分是______、______.

(2)在“测定种子的发芽率”探究活动中,老师将500粒玉米种子平分给初1•1班五个实验小组进行实验,结果5天后,三个小组看到分别有9、8、5、7、6粒未发芽,那么初1•1班所测定的这批种子的发芽率应为______.

(3)“小麦清明拔三节,新笋一夜成高竹”,这是对某些植物的______现象的描述.

(4)秋天在收获玉米时,常会发现玉米果穗有缺粒的现象,原因是______不足,为了避免这种现象的发生,可以采用______方法来弥补.

答案

(1)种子的成分包括有机物(淀粉、蛋白质和脂肪)和无机物(水和无机盐),点燃有机物变成二氧化碳和水散发掉,水受热蒸发,剩下就是无机盐.淀粉遇碘变蓝色是淀粉的特性,双缩脲与蛋白质接触后的颜色呈紫色.因此可用碘液和双缩脲分别检验淀粉和蛋白质.

(2)种子的发芽率=已萌发的种子数/种子总数,已萌发的种子数=91+92+95+93+94=465,种子的发芽率=465/500×100%=93%.

(3)单子叶植物茎的结构是茎节之间有居间形成层,单子叶植物茎的生长就是靠居间形成层.

(4)玉米是异花传粉植物当传粉不足时容易产生缺粒现象,为避免这种现象通常采用人工辅助授粉的方法给玉米授粉来提高产量.

故答案是:(1)淀粉;碘液;蛋白质;双缩脲;无机盐;水;脂肪 (2)93% (3)居间生长 (4)传粉不足;人工辅助授粉.

解答题
阅读理解

People who are hit by lightning and survive often have long-term effects. These may include memory loss, sleep disorders, muscle pain and depression(郁闷).

Experts tell people to seek(寻找) the safety of a building or a hard-top vehicle any time they hear thunder, even if it is not raining. They say lightning can strike as far as sixteen kilometers from any rainfall. Lightning can travel sideways. And at least ten percent of lightning happens without any clouds overhead that you can see.

People who are outdoors should make sure they are not the tallest thing around. Bend(屈身) low to the ground, but do not lie down. And do not stand near a tree or any tall object. Get away from water and anything made of metal. A car is safe, but do not touch any metal inside.

Safety experts say people in buildings should stay away from anything with wires or pipes that lead to the outside. The National Weather Service says if you plan to disconnect any electronic equipment, do so before the storm arrives. Do not use a wired telephone. Do not use water. All these can carry electricity.

Some people think a person struck by lightning carries an electrical charge (电荷) afterward. Experts say this is not true. It is safe to begin emergency treatment.

Each year about four hundred people in the United States are struck by lightning. Last year forty four people died. The average(平均) is close to seventy. The National Weather Service says that is more than the number of people killed by severe storms.

小题1:According to the passage, which of the following is NOT true?

A.Lightning can happen even if there is no cloud.

B.Lightning won’t do harm to people’s health.

C.Lightning can travel sideways.

D.Lightning can strike very far.小题2:The underlined word “disconnect” (in Paragraph 4) refers to “_______”.

A.cut out

B.interrupt

C.disturb

D.cut off小题3:Which of the following mustn’t you do in order to seek lightning safety?

A.Hide in a building.

B.Sit in a car.

C.Bend low to the ground.

D.Lie under a tall tree.小题4:Which of the following is the main idea of the passage?

A.The latest information about lightning.

B.Some common knowledge about lightning safety.

C.How lightning comes into being.  

D.Where we should hide in case of lightning.