问题
名词解释
杂种优势
答案
参考答案：所谓杂种优势是指两个或两个以上不同遗传类型的个体杂交所产生的杂种第一代，往往在生活力、生长速度和生产性能等方面优于两个亲本种群平均值的现象。
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杂种优势
参考答案：所谓杂种优势是指两个或两个以上不同遗传类型的个体杂交所产生的杂种第一代，往往在生活力、生长速度和生产性能等方面优于两个亲本种群平均值的现象。
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| Big Ben? It's not the name of a person. It's a famous 1 in London. It is part of a very big clock at the top of a tower (塔). The minute hands of the clock 2 more than four metres long. The clock has four 3 . You can see what 4 it is from any side (面). The name of the bell comes 5 Sir Benjamin Hall. The tower is about 150 years old. The bell makes a loud 6 every hour. On New Year's Eve, millions of people listen to it on TV!
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