1. History of Life on Earth

2. Fig. 25-7 Animals Colonization of land Paleozoic Meso- zoic Humans Ceno- zoic Origin of solar system and Earth Prokaryotes Proterozoic Archaean Billions of years ago 1 4 3 2 Multicellular eukaryotes Single-celled eukaryotes Atmospheric oxygen

3. Oparin and Haldane hypothesized that the early atmosphere was highly electrical Stanley Miller and Harold Urey conducted lab experiments that showed that the abiotic(non- living) synthesis of organic molecules in the early atmosphere is possible They spent years researching and trying to recreate a closed system that mimic what they believed to be the conditions of early Earth.