种群的年龄结构是每一年龄阶段个体数目的比率，通常用（ ）表示。

试卷相关题目

SQL Error: select id,body,options from ***_enewstiku where sourceid='29863' and id < 2422598 and id<>'2422598' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='29863' and id > 2422598 and id<>'2422598' order by id asc limit 5