The bacteria that first grew on land evolved to survive in the harsh environment of ultraviolet sun rays, desert conditions, and lack of oxygen.
The bacteria churned the rock into sediment, without which future land plants probably would not have been able to take root. It also provided plants with nutrients in the form of minerals on which to survive.
During the Silurian period, which followed the Ordovician period, forests of fern-like trees evolved. By the end of the Devonian period, some 360 million years ago, a varied plant population extended all over Earth’s land masses.