Precambrian

Precambrian

What plants and animals lived in the Precambrian era? - TimesMojo

Geology - Grand Canyon National Park (U.S. National Park Service)

Imagine an Earth where oxygen was poison. That was our planet for its first two billion years! Around 2.5 billion years ago, the entire atmospheric composition changed forever, thanks to one incredible microorganism: cyanobacteria. Cyanobacteria evolved photosynthesis, the process of using sunlight, water, and $text{CO}_2$ to create energy, releasing pure oxygen ($text{O}_2$) as a waste product. Initially, this $text{O}_2$ was captured by iron in the oceans, forming vast deposits known as Banded