biological variability 基本例句 生物差异 They have speculated about why human populations have different physical appearances and about whether the biological differences between groups are more than skin deep.对于人群间体表差异的起源,早就有许多猜测,至于人群间的生物差异究竟只限于肤浅处,还是深刻得多,更是议论纷纷。