1. 3 evolution and diversity of microbial cells: first microbial activity 3. 8-3. 9 billion years ago, first 2 billion years the atmosphere had no oxygen. Cyanobacteria started oxygenation 3 bya: 80% of life"s history was microbial, 3 domains of life: bacteria, archaea and eukarya, phylogeny of microbial organisms can be constructed by examining the genome. One method to do so is to examine genes that encode r-rna (ribosomal rna): archaea are more related to eukarya than to bacteria. Robert hooke english mathematician, historian and microscopist: micrographia book with microscopic observations, described the fruiting structure of molds. Antoni van leeuwenhoek draper and amateur microscopist: constructed simple microscopes with a single lens, discovered bacteria in 1676 and drew them. Ferninand cohn botanist: he was interested in bacteria that are heat resistant, discovered that some bacteria form endospores by differentiation which are heat resistant, proposed sealing flasks and tubes with cotton to avoid contamination of culture media.