问题 解答题

根据探究“绿叶在光下制造淀粉”的实验回答:

(1)实验前,请你设计一个简单的方案,以排除叶片中原有淀粉对实验的影响:

(2)将暗处理过的天竺葵的一片叶部分遮光、部分不遮光的目的是______,将植物放在阳光下照射几小时后,摘下这片叶放在酒精中水浴加热,其目的是______,为什么要隔水加热?______.

(3)右图示步骤(3)中用酒精处理的叶片,A是遮光部分,B是见光部分.用清水冲洗叶片后,在上面滴加碘液,其中变蓝色的是______.此实验说明了绿叶只能在不遮光下产生______.

答案

该实验的方法步骤:暗处理→部分光照→光照→摘下叶片→酒精脱色→漂洗加碘→观察颜色→分析现象,得出结论.

(1)暗处理:把盆栽的天竺葵放到黑暗处一昼夜,目的是为了让天竺葵在黑暗中把叶片中的淀粉全部转运和消耗,这样实验中用碘液检验的淀粉只可能是叶片在实验过程中制造的,而不能是叶片在实验前贮存.

(2)部分遮光:用黑纸片把叶片的一部分从上下两面遮盖起来,然后移到阳光下照射.是为了设置对照.此实验中的变量是光照.目的:看看照光的部位和不照光的部位是不是都能制造淀粉.这样做就确定绿叶中的淀粉只有在光下制造的,黑暗中不能光合作用;把叶片放入盛有酒精的小烧杯中,隔水加热.目的是用酒精溶解叶片中的叶绿素,叶片变成黄白色.便于观察到淀粉遇碘变蓝的颜色反应;装有酒精和叶片的小烧杯,一定要隔水加热.这是因为酒精是易燃、易挥发的物质,直接加热容易引起燃烧发生危险.使用水对酒精进行加热,起到控温作用,以免酒精燃烧发生危险.

(3)淀粉遇碘变蓝色,B遇碘变蓝,说明这里产生了淀粉,A遇碘没有变蓝,说明这部分没有淀粉产生,所以,绿叶只有在光下才能产生淀粉,淀粉是光合作用的产物.

故答案为:(1)实验前,将一盆生长旺盛的天竺葵放入黑暗中一昼夜(或24小时);(2)在叶片上形成见光与不见光的对照(或形成对照);将叶片中的叶绿素溶解到酒精中(或脱去绿叶中的叶绿素);防止温度过高,引燃酒精;(3)B;淀粉.

单项选择题

St. Patrick’s Day is celebrated on March 17, his religious feast day and the anniversary of his death in the fifth century. Legend has it that this patron saint had given a sermon from a hilltop that drove all the snakes from Ireland. He also used the three-leafed shamrock to represent the Trinity how the Father, the Son, and the Holy Spirit could all exist as separate elements of the same entity—and converted the pagans to Christianity. The Irish have observed this day as a religious holiday for hundreds of years. People wear green in memory of the Emerald Isle and wear shamrocks.

The first St. Patrick’s Day parade, however, took place not in Ireland, but in the United States. Irish soldiers serving in the English military marched through New York City on March 17, 1762. Along with their music, the parade helped the soldiers, as well as fellow Irishmen serving in the English army, to reconnect with their Irish roots.

Over the next thirty-five years, Irish patriotism among American immigrants flourished, prompting the rise of so-called "Irish Aid" societies, like the Friendly Sons of Saint Patrick and the Hibernian Society. Each group would hold annual parades featuring bagpipes (which actually first became popular in the Scottish and English armies) and drums.

Up until the mid-nineteenth century, most Irish immigrants in America were members of the Protestant middle class. When the Great Potato Famine hit Ireland in 1845, close to a million poor, uneducated, Catholic Irish began to pour into America to escape starvation. Despised for their religious beliefs and funny accents by the American Protestant majority, the immigrants had trouble finding even menial jobs. When Irish Americans in the country’s cities took to the streets on St. Patrick’s Day to celebrate their heritage, newspapers portrayed them in cartoons as drunk, violent monkeys.

However, the Irish soon began to realize that their great numbers endowed them with a political power that had yet to be exploited. They started to organize, and their voting block, known as the "green machine," became an important swing vote for political hopefuls. Suddenly, annual St. Patrick’s Day parades became a show of strength for Irish Americans, as well as a must-attend event for a slew of political candidates. In 1948, President Truman attended New York City’s St. Patrick’s Day parade, a proud moment for the many Irish whose ancestors had to fight stereotypes and racial prejudice to find acceptance in America.

St. Patrick’s legendary feats in Ireland does NOT include ().

A. representing the Trinity with a plant

B. changing the belief of pagans

C. getting snakes out of Ireland

D. making people wear costume

问答题