According to this definition, one species is distinguished from another by the possibility of matings between individuals from each species to produce fertile offspring.
根据这一定义，区分不同物种的标准是不同物种的个体间相互交配产生可育后代的可能性。
“It is likely that perfect 0.7 ratio sends a biological signal to men that that woman is most fertile and most likely to produce a healthy offspring, no matter what size that woman is, ” he said.
他说“有可能完美的0.7比例向男性传递着一种生理信号，无论该女性的整体尺寸如何，0.7的比例意味着女性的生育能力更强，更容易产下健康的后代。”
Stirling said polar bears and grizzlies have been successfully paired in zoos and that their offspring are fertile, but there had been no documented case in the wild.
报道说，此前，北极熊和灰熊曾在动物园内被配对成功，而且它们还生下了后代。 北极熊和灰熊这两种不同种类的熊，其繁殖期大致相同，但相比较而言，北极熊的繁殖期要比灰熊来得稍稍早一些。
Stirling said polar bears and grizzlies have been successfully paired in zoos and that their offspring are fertile, but there had been no documented case in the wild.
报道说，此前，北极熊和灰熊曾在动物园内被配对成功，而且它们还生下了后代。 北极熊和灰熊这两种不同种类的熊，其繁殖期大致相同，但相比较而言，北极熊的繁殖期要比灰熊来得稍稍早一些。
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