中文摘要：

分析了一类带有性别比的两阶段尺度结构种群模型．利用特征线方法和比较原理证明了状态系统解的存在唯一性．借助上一下解技巧分别给出了目标种群灭绝和长期生存的条件．

英文摘要：

This work is concerned with a nonautonomous size-structured juvenileadult model with fixed sex-ratio. Existence and uniqueness of solutions to the basic system are proved by means of characteristics and a comparison principle. Extinction and persistence results are established via the upper-lower solution technique.