The Cambrian marked a profound change in life on Earth: prior to the Cambrian, the majority of living organisms on the whole were small, unicellular and simple (Ediacaran fauna and earlier Tonian Huainan biota being notable exceptions).
Prior to the Cambrian period, most life forms were tiny, single-celled, and uncomplicated. The Ediacaran fauna and earlier Tonian Huainan biota represent notable exceptions.