To appreciate the impact life has had on this planet Outline 1. Life appears Photosynthesis evolves Free oxygen accumulates in the atmosphere Eukaryotes evolve through endosymbiosis Multicellular life evolves For most of earth's history, microbes have been the dominant life form. Flood basalts in Siberia may have played a role. The Mesozoic ends with another mass extinction, wiping out the dinosaurs and other groups. Flood basalts in India, and an asteroid striking what is now the Yucatan Penninsula in Mexico may have caused it.
Grasses evolve, allowing an adaptive radiation of rodents and snakes.
A period of ice ages begins 2 mya. We are in a brief interglacial period between glaciations.