Population is a group of individuals of the same species that live in the same area.
种群是占有一定空间和时间的同一物种个体的集合体。
Community is a group of different populations that live together in a defined area.
群落是占有一定空间和时间的多种生物种群的集合体。
Ecosystem is all the organisms that live in a place，together with their physical environment.
生态系统是指在一定的空间内生物成分和非生物成分通过物质循环和能量流动而相互作用、相互依存而构成的一个生态学功能单位。
