At first glance, abiotic factors such us climate change, transgressive-regressive sea level cycles, plate movements, tectonic processes, and the type and intensity of vol- canism appear very significant in the shaping of biotic evolution. We can see how rapid rates of subsidence, as expressed in transgressive system tracts on the Australian cra- ton, selectively affected the diversity of organisms such as trace fossil producers, ar- chaeocyath sponges, and trilobites (Gravestock and Shergold — chapter 6); how glob- ally increased rates of subsidence and uplift accompanied dramatic biotic radiation by increasing habitat size and allowing phosphorus- and silica-rich waters to invade platform interiors (Brasier and Lindsay — chapter 4); how climatic effects, coupled with intensive calc-alkaline volcanism, at the end of the Middle Cambrian may have caused a shift from aragonite- to calcite-precipitating seas, providing suitable con- ditions for development of the hardground biota (Seslavinsky and Maidanskaya — chapter 3; Eerola — chapter 5; Guensburg and Sprinkle — chapter 19); how the re- organization of plate boundaries (Smith — chapter 2; Seslavinsky and Maidanskaya) created conditions for current upwelling, which may in turn have been responsible for the appearance and proliferation of acritarch phytoplankton and many Early Cam- brian benthic organisms (Brasier and Lindsay; Ushatinskaya — chapter 16; Moldowan et al.— chapter 21).