题干

为探究种子萌发的环境条件,杨明同学设计了如下实验:在甲、乙、丙、丁四个培养皿内分别放等量的棉花,在棉花的上面都放入25粒大小相同豌豆种子,然后将它们放在不同条件下进行培养,数日后记录种子萌发的情况如下表,请分析回答:

装置

甲

乙

丙

丁

场所

黑暗中

黑暗中

日光下

日光下

温度

23℃

23℃

23℃

23℃

棉华干湿状态

潮湿

(含一定水分)

干燥

潮湿

(含一定水分)

干燥

种子萌发数量

23

0

24

0

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       Look carefully at the back of a California state quarter. A man with a walking stick is pictured there. A bird called a California condor(大秃鹫)is flying overhead. Who is this man, and why is he so important that he is featured(处于显著地位)on the back of a coin?
      The man on this quarter is John Muir. Even as a child, Muir loved watching nature. As a young man, he spent much of his life exploring the beauty of the wilderness. He walked more than a thousand miles across the country, through fields and woods. John Muir liked writing about the places he visited, describing their beauty.
       Muir also wrote about problems. In order to create more farmland for sheep and cattle, many trees were being cut down. This made Muir unhappy and worried, because he knew that trees were important to forests and to the animals that lived in them.Muir believed that nature should be conserved(保护)instead of being changed by human beings. He wrote articles in magazines and newspapers to spread the word about conserving forests. Soon, others began to listen.
       Muir wrote letters to important people, such as President Theodore Roosevelt. The president admired Muir’s love for nature. When Roosevelt came to visit Muir in California. Muir convinced(说服)the president to go camping with him for three nights under the trees so they could talk about conservation. Later, President Roosevelt set aside 148 million acres of land for national forests and established(建立)five national parks. National parks are large areas of land that are protected from development. This means that people cannot build homes or businesses there. One of these parks is Yosemite National Park, the area that is featured on the back of the California quarter.
     Though it has been almost one hundred years since John Muir died, people continue his work today. His work as a conservationist helped us to see the beauty of our natural world. John Muir made us understand the importance of protecting our earth and our resources---then, now, and for the future.