Eukaryotes need nitrate for metabolism, cyanobacteria can use N 2 directly. Early eukaryotes probably reproduced asexually, since they were basically crude aggregates or colonies of prokaryote-like cells. Most well-known are members of the Ediacarian fauna, first discovered in south Australia, but now known to occur at other localites. They were probably preserved only locally by accident, but lack of predators may have played a role. Ozone layer develops, providing protection from UV radiation.
Organisms develop hard parts, providing additional protection from UV and predation.
The Neoproterozoic saw an increase in primary productivity and the burial of Metazoan excrement in deep-marine sediments. O high during this time. Caused by overturning of marine water column by influx of deep, cold oxygenated water currents. Side effect of carbon burial is increased oxygen in atmosphere, since there is less unburied carbon available for oxidation.