问题 解答题

甲状腺激素有促进蝌蚪发育的作用.现提供40只大小、发育状况相似的蝌蚪、两个玻璃缸、水草、清水、不含任何激素的食物、甲状腺活性物质等材料.请你完成以下实验,验证甲状腺激素的作用:

(1)实验变量:______.

(2)实验设计:

①两个玻璃缸分别编号为A和B,各放入______只蝌蚪、适量清水、少量水草,每天同时喂食.

②A缸______;B缸______.

③______.

(3)实验结果:______.

(4)得出结论:______.

答案

(1)设置对照实验的关键是一组对照实验中只能有一个变量,这样才能看出实验结果与变量的对应性;该实验小组探究的是甲状腺激素有促进生物体生长发育的作用,因此变量是否加入甲状腺活性物质.

(2)探究实验要通过对比得出科学的结论,保持变量的唯一是设置对照实验的关键,本实验除了否加入甲状腺活性物质不一样,其它条件都一样,可设计为:①两个玻璃缸分别编号为A和B,各放入20只蝌蚪、适量清水、少量水草,每天同时喂食.②A中每天加入适量甲状腺活性物质,B中不加入甲状腺活性物质,其它条件一样,目的是形成一组以甲状腺激素为变量的对照实验.③每天做好观察记录.

(3)有分析可知,甲状腺激素的主要作用是促进新陈代谢、促进生长发育、提高神经系统的兴奋性.故实验结果预期是:A组提前发育为成蛙(个体小),B组按正常时间发育.

(4)通过对照试验的结果,可得出结论:甲状腺激素有促进蝌蚪发育的作用.

故答案为:(1)是否加入甲状腺活性物质;

(2)①20;②每天加入适量甲状腺活性物质;不加入甲状腺活性物质;③每天做好观察记录;

(3)A组提前发育为成蛙(个体小),B组按正常时间发育;

(4)甲状腺激素有促进蝌蚪发育的作用.

阅读理解

Akuapem is in the eastern part of Ghana. The sun there shines all the time. The local people are very friendly and hospitable(好客的). Now let’s have a look at how Akuapem people receive a visitor.

A visitor is often welcomed warmly in a family of Akuapem. After the visitor is welcomed into the house, he is offered a seat and water at the very beginning, because the host assumes that the visitor must have come from a very long journey and need water. If there is a group of visitors, the host will greet the visitors from right to left. And the host shakes only with his right hand, because Akuapem people think the left hand is not clean.

Next, the visitor is asked how his journey was and why he has come. While the conversation is going on, the wife and the children, especially girls, are preparing food for the visitor. The visitor can choose his favorite food. After the visitor finishes eating, the host and the visitor go on with their conversation. Usually this is short one because the visitor is getting ready to say goodbye.

When the visitor is leaving, he is often given some food. He is also accompanied(陪伴) by one of the children to the nearest station. The child who accompanies the visitor will not come back home until the visitor leaves safely.

Whether he is a close friend or just a stranger, this is always how friendly Akuapem people receive a visitor.

小题1:The underlined word “assumes” here probably means “   ”.

A.thinks

B.remembers .

C.disagrees

D.follows小题2:Which of the following is TRUE to the passage?

A.The host talks little with the visitor.

B.The child accompanies the visitor to the gate of the house.

C.The host offers the visitor a seat only.

D.The visitor takes some food with him when he leaves.小题3: From the passage we know that Akuapem people are         .

A.noisy

B.friendly

C.impolite

D.quiet

选择题