1) The document outlines the major geologic periods from the Precambrian era to today. It describes key events, climate conditions, dominant species and organisms, formation and breaking up of continents, and mass extinctions that occurred during each period.
2) The periods discussed include the Precambrian, Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Tertiary, and Quaternary periods.
3) Details are provided on the environments and lifeforms that existed during important transitions, such as the first appearance of oxygen, land, trees, dinosaurs, mammals and modern humans.