Van leeuwenhoek first discovered microorganisms in 1684. Microbes affect human beings bc they can cause diseases, they"re used for digestion, for food, environment, and in biotechnology and medicine. Metabolism, growth, reproduction, and homeostasis is common in all life forms. 4 main macromolecules in microbial cells: polypeptides, nucleic acid, lipids, and polysaccharides. Polypeptides are proteins that function as enzymes (catalysts of chemical reactions) Lipids are what make up the plasma membrane (pm) In 1970, carl woese classified bacteria, archaea, and eukarya based on phylogenies. Origin of life ( 3. 8 bya with microbes) First oxygen producing bacteria ( 3 bya) Oxygen atmosphere was established ( 2 bya with eukaryotes) Endosymbiosis ( origin of eukaryotes from prokaryotes) Multicellular organisms, euk, land plants, animals, ( . 5 bya) Earlier cells used rna, the rna replicated and formed a membrane and. 2nd chloroplasts the rna was used to code and produce proteins ( enzymes) Later on, dna evolved because it was more stable than rna.