biotic formation

• 生物群系

biotic formation的用法和样例：

例句

1. Associations differed from one another in response to climatic differences within the region of the formation.
   群众之间的差异反映了在群系分布范围内的气候的差异。
2. Periods of volcanism are indicated by the presence of pyroclastic material in the formation.
   群系中火成碎屑物的存在表明了火山酌的形成年代。