这就要考虑狗的物种变异，族类，智力，表情和身体特性。
For this to happen the variables of species, breed, intellect, emotion and the physical traits of the canine have to be considered.
许多科学家都认为，国内的狗更显示形态比任何其他已知的物种变异，人类有选择育种的感谢。
Many scientists agree that the domestic dog displays more morphological variation than any other known species, thanks to selective breeding by humans.
正是在环球航行返回几个月之后，达尔文才第一次真正严肃地思考进化- - -或者“物种变异的”可能性。
It was a few months after returning from this voyage that Darwin first began to consider seriously the possibility of evolution, or the "transmutation of species."
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