题干

在某岛屿上相互隔绝的甲、乙两个水潭中,都生活着小型淡水鱼——虹鳉。研究发现,甲中的虹鳉(天敌是狗鱼,以大而成熟的虹鳉为食)比乙中的虹鳉(天敌是花鳉,以幼小的虹鳉为食)常常早熟,即在体重较低时就能繁殖后代。下列观点不正确的是(   )

A:两个虹鳉种群中都有成熟早或晚的变异类型,这是进化的前提条件

B:甲中的早熟型个体有更多的机会繁殖后代,因而种群中早熟基因的基因频率增加

C:因为甲、乙中的两个虹鳉种群存在地理隔离,所以它们属于不同的物种

D:若将甲中的虹鳉和乙中的花鳉转移到一个新水潭中共同饲养,多年后虹鳉成熟个全的平均体重将会增加

上一题 下一题 0.0难度 选择题 更新时间:2020-01-16 11:14:59

答案(点此获取答案解析)

C

同类题1

完形填空

    Alice was very worried about her dad. For some time now she had noticed he was 1 his hair. One day, she asked him, “Daddy, every day you have less hair.2 is that?” Her father smiled and said, “It's the hair thief. He visits my head during the night when I'm 3. One by one he 4 out my hair, as much as he likes.”

    This worried Alice but she was 5 to help her father. That very night she stayed 6 as long as she could. When she was 7 her dad and mom had fallen asleep, she took a hammer and went straight to their bedroom. She walked carefully in order not to make any 8. She didn't want the hair thief to hear her. Then she began carefully 9 her father's head. When she arrived at her father's side, she began looking at his head,10to catch the hair thief as soon as he appeared. Before long, she saw a shadow on it and 11 all her strength, she swung the hammer down.

    Thwack! Her father 12a loud cry. The lump(肿块) on his head was big and growing.13 with shock, he turned the light on and saw Alice waving her hammer in the 14 with her hands. “Daddy, I 15 got him. I thought I 16 him, but it looks like he escaped!” said Alice. At the same time, the mother woke up. She 17laughing when she knew what had happened.

    So Alice's father had to 18to her that the hair thief didn't exist, and that losing hair is something that just happens 19 to most daddies. And Alice still worried about her daddy, but she no longer waited for the hair thief.20 , she bought her daddy a very nice sleeping hat.