蒲公英种群密度取样调查过程是（  ）　　
①随机选取若干样方　②计数每个样方的个体数目　③确定某一地段中的蒲公英为调查对象　④计算种群密度　⑤求每个样方的种群密度

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                                                                                                       燕子

                                                                                                            席慕容
       初中的时候，学会了那一首《送别》的歌，常常唱：长亭外，古道边，芳草碧连天……
       有一个下午，父亲忽然叫住我，要我从头再唱一遍。很少被父亲这样注意过的我，心里觉得很兴奋，赶快再从头来好好地唱一次：长亭外，古道边……
       刚开了头，就被父亲打断了，他问我：“怎么是长亭外？怎么不是长城外呢？我一直以为是长城外啊！”
       我把音乐课本拿出来，想要向父亲证明他的错误。可是父亲并不要看，他只是很懊丧地对我说：“好可惜！我一直以为是长城外，以为写的是我们老 家，所以第一次听这首歌时就特别地感动，并且一直没有忘记，想不到竟然这么多年听错了，好可惜！”
       父亲一连说了两个好可惜，然后就走开了，留我一个人站在空空的屋子里，不知道如何是好。
       前几年刚搬到石门乡间的时候，我还怀着凯儿，听医生的嘱咐，一个人常常在田野间散步。那个时候，山上还种满了相思树，苍苍翠翠的，走在里面，可以听到各式各样的小鸟的鸣声。田里面也总是绿意盎然，好多小鸟也会很大胆地从我身边飞掠而过。
       我就是那个时候看到那一只孤单的小鸟的，在田边的电线杆上，在细细的电线上，它安静地站在那里，黑色的羽毛，像剪刀一样的双尾。“燕子！”我心中像触电一样地呆住了。
       可不是吗？这不就是燕子吗？这不就是我从来没见过的燕子吗？这不就是书里说的，外婆歌里唱的那只燕子吗？
       在南国的温热的阳光里，我心中开始一遍一遍地唱起外婆唱的那一首歌来了：
       燕子啊！燕子啊！你是我温柔可爱的小小燕子啊……
       在以后的几年里，我都会常常看到这种相同的小鸟，有的时候，我是牵着慈儿，有的时候，我是抱着凯儿，每一次，我都会兴奋的指给孩子看：“快看，宝贝，快看！那就是燕子，那就是妈妈最喜欢的小小燕子啊！”
        怀中的凯儿正咿呀学语，香香软软的唇间也随着我说出一些不成腔调的儿语。天好蓝，风好柔，我抱着我的孩子，站在南国的阡陌上，注视着那一只黑色的安静的飞鸟，心中充满了一种朦胧的欢喜和一种朦胧的悲伤。
       一直到了去年的夏天，因为内政部的邀请，我和几位画家朋友一起，到南部国家公园去写生，在一本报道垦丁附近天然资源的书里，我看到了我的燕子。图片上的它有着一样的黑色羽毛，一样的剪状的双尾，然而，在图片下的注释和说明里，却写着它的名字是“乌秋”。
       在那个时候，我的周围有着好多的朋友，我却在忽然之间觉得非常的孤单。在我的朋友里，有好多位是在这方面很有研究心得的专家，我只要提出我的问题，一定可以马上得到解答，可是，我在那个时候惟一的反应，却只是把那本书静静地合上，然后静静地走了出去。
       在那一刹那，我忽然体会出来多年前的那一个下午，父亲失望的心情了。其实，不必向别人提出问题，我自己心里也已经明白了自己的错误。但是，我想虽然有的时候，在人生的道路上，我们是应该面对所有的真相，可是，有的时候。我们实在也可以保有一些小小的美丽的错误，与人无害，与世无争，却能带给我们非常深沉的安慰的那一种错误。
      我实在是舍不得我心中那一只小小的燕子啊！
相关链接：席慕容——台湾著名诗人、散文家。1943年生于重庆城郊，祖籍蒙古察哈尔盟明安镇，1948年于南京入小学，1949年迁至香港，1954年迁至台湾。1989年后多次访问家乡、大陆。

    Our brains work in complex and strange ways. There are some people who can calculate the day of the week for any given date in 40,000 years, but who cannot add two plus two. Others can perform complex classical piano pieces after hearing them once, but they cannot read or write.

    Dr. J. Langdon Down first described this condition in 1887. He called these people idiot savants. An idiot savant is a person who has significant mental injury, such as in autism (自闭症) or retardation. At the same time, the person also exhibits some extraordinary skills, which are unusual for most people. The skills of the savant may vary from being exceptionally gifted in music or in mathematics, or having a photographic memory. One of the first descriptions of a human who could calculate quickly was written in 1789 by Dr. Benjamin Rush, an American doctor. His patient, Thomas Fuller, was brought to Virginia as a slave in 1724. It took Thomas only 90 seconds to work out that a man who has lived 70 years, 17 days, and 12 hours has lived 2,210,500,800 seconds. Despite this ability, he died in 1790 without ever learning to read or write.

    Another idiot savant slave became famous as a pianist in the 1860s. Blind Tom had a vocabulary of only 100 words, but he played 5,000 musical pieces beautifully.

    In the excellent movie Rain Man, made in 1988 and available on video cassette, Dustin Hoffman plays an idiot savant who amazes his brother played by Tom Cruise, with his ability to perform complex calculations very rapidly.

    Today we more clearly recognize that the idiot savant is special because of brain impairment. Yet not all brain injury leads to savant skills. Some studies have shown that people who have purposeful interruption of the left side of the brain can develop idiot savant skills. However few people wish to participate in such experiments. There are many excellent reasons for not undergoing unnecessary experimentation on one’s brain. The term idiot savant is outdated and inappropriate. Virtually all savants have a high degree of intelligence and are thus not idiots.