20世纪80年代，美国在亚利桑那州的沙漠上建造了一个实验基地“生物圈Ⅱ号”．

（1）你对“生物圈Ⅱ号”有何了解？

（2）科学家在“生物圈Ⅱ号”中进行的探索虽然没有完成预定的计划，但是它用事实告诉了人们一个道理．这个道理是什么？

____植物具有真正的根、茎、叶。

假如你叫大明，收到了你的英国朋友Tony的来信，信中他很关心四川雅安地震后学生的情况。请你根据他的来信内容写一封回信，感谢他对灾区学生的关心，回答他的问题，并谈谈你的感受。
提示词语：thank you, care to， go on， government ，offer，encourage， brave　
Dear Daming,
I'm sorry to hear that a big earthquake happened in Ya'an, Sichuan. Some school buildings broke down in the earthquake and many students couldn't go to school. But I know the government is trying their best to help them. And Chinese people are so strong and brave that they aren’t afraid of anything difficult. Can the students go on studying now? Please tell me more about them.
I'm looking forward to hearing from you soon.
Yours, 
Tony
Dear Tony,
I'm glad to hear from you
Best wishes.  
Yours
Daming

数百年前，我国黄土高原有茂密的森林．后来由于人口过于集中和长期掠夺式的开发等原因，变成了荒山秃岭．这个现象说明（  ）