BIOLOGICAL RESPONSES TO EUSTATIC CYCLES

Through studies of the sequence stratigraphy and biostratigraphy of the Cambrian Qiongzhusian Stage and the Silurian Qujing basin in Yunnan, the author found that there are certain relationships （or called responses） between organisms and eustatic cycles. （1） Morphological response: In the evolutionary sequence of trilobites in the Qiongzhusian Stage this response is manifested by the fact that the process of sealevel fall is favorable to the formation of endemic forms, while the sealevel rise results in the immigration of allopatric forms. （2） Community response: Each eustatic cycle will result in reorganization of benthic marine communities, forming a new biotic assemblage. （3） Population response: It is usually marked by the fluctuation of the population size, which is in essence interpreted as different manifestions of a population in different habitats.