英国的曼彻斯特地区有一种桦尺蛾，原来黑尺蛾仅占1%，灰尺蛾占99%，建立工业区以后50年，黑尺蛾占99%，灰尺蛾仅占1%。发生上述变化的原因是（）
A.黑尺蛾大量迁入，灰尺蛾大量迁出所致
B.控制灰色的隐性基因突为显性基因所致
C.黑尺蛾与灰尺蛾的繁殖能力发生了变化
D.环境对变异进行了定向的选择，改变了种群的基因频率
参考答案：D
解析：
种群基因频率定向改变，源于环境的定向选择作用
考点：本题考查环境选择对生物进化的影响，意在考查考生理解所学知识要点。
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| Many children have birthday cakes on their birthdays. In some ___1___, like England and Scotland, there is another custom, too. People beat or hit the___2___on his/her birthday. This may hurt___3___, but they say it is very lucky for the child. The child must ___4___cry. The custom says, if you ___5___, you will cry all year. They say the birthday spanks (一巴掌) is to make the bad spirits(邪气) ___6___. The harder you spank the better. In Belgium, another country in Europe, the custom is a little __7___. There a parent goes into the child's room ___8___in the morning with a needle. As soon as the child ___9___ up, the parent pricks(刺) the child with the needle. This is for good __10____. | ||||
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