题干

如图是物种形成的一种模式。物种a因为地理障碍分隔为两个种群a1和a2,经过漫长的进化,分别形成新物种b和c。在此进程中的某一时刻,a1种群的部分群体越过障碍外迁与a2同域分布,向d方向进化。下列有关叙述正确的是(   )


A:b和d存在地理隔离,所以一定存在生殖隔离

B:c和d不存在地理隔离,却可能存在生殖隔离

C:a1中的外迁群体与当时留居群体的基因频率相同,则b和d是同一物种

D:a1中的外迁群体与当时a2种群的基因频率不同,则c和d是不同物种

上一题 下一题 0.0难度 选择题 更新时间:2012-09-11 11:40:56

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B

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    A cat is recovering in California after surviving a 6,500-mile journey across the Pacific stowed inside a Chinese shipping container without food or water. Staff and volunteers have named it “Ni Hao”, which is Chinese for “hello”.

    It was discovered breathing shallowly after a two-week trip across the Pacific Ocean. The cat was seriously suffering from loss of water and starvation when the container was opened in California last week, but was said to be doing well after being sent to the Carson Animal Care Centre in Los Angeles. At first it was too weak to stand, but finally took its first steps. Then it ate a good meal and slept soundly. The cat woke up on Thursday morning, physically in a better condition than 24 hours ago.

     “Ni Hao greeted the medical team with its first meow this morning and is attempting to stand,” said Marcia Mayeda, head of the Los Angeles Department of Animal Care and Control. Aaron Reyes, director of the Department, added, “We finally got to hear its voice. It sounds like a single-engine plane.”

    Ni Hao is expected to be observed for 60 days but afterwards animal workers will look forward to providing it with a good shelter. “It's much better for it to recover in a home environment,” Mr. Reyes said. “It's just like a human being in a hospital so we're hoping to move it.” He added, “Little by little we're getting there. We're hoping that under the treatment and with rest, it'll be able to recover quickly.”

    It was not immediately clear how the cat got into the container.