genetic drift and small gene changes can plausibly account for the evolution of new genera, families, and orders. Investigators are exploring these areas using traditional methods as well as the newer techniques of molecular biology.生物学家还无法回答关于大规模进化的许多问题。许多问题是新类别的物种可能起源于还不确定的遗传过程，或者知道遗传过程，例如，遗传漂移和少量基因的改变可能是新属，科，目产生的原因。科研工作者不但利用传统方法对这些领域进行研究，还利用分子生物学新科技。
Populations of a species that are spread out over a broadgeographical range are often arrayed in a cline-a gradual change in one or morecharacteristics as each population evolves adaptations to its own localenvironment. Along a cline, subspecies with distinct characteristicsmay arise. Often, individuals at either end of a cline arereproductively isolated.地域上分布很广的种的群体中，经常存在变异群，因为适应当地的环境，每个群体逐渐产生一个或多个与众不同的特点。在变异群中，带有明显特征的亚群可能产生。通常，在两个变异群中的个体是繁殖隔离的。
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