Many scientists agree that the domestic dog displays more morphological variation than any other known species, thanks to selective breeding by humans.
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。
2
The researches about the classification and identification of their species and varieties have provided an early, subservient and selective index for breeding work.
其种间或品种间的分类鉴定和亲缘关系的研究为育种工作提供了一个早期的、辅助的、选择性的指标。
3
Pushed to the brink of survival, the Kaminoans perfected cloning technology and practiced selective breeding to keep their species viable.