Chapter 27: bacteria and archaea 1. identify the differences between bacteria, archaea, and eukarya, and the evolutionary relationships between the 3 groups 2. explain the ecological roles of prokaryotes: decomposers, producers, nitrogen fixers, pathogens, and various symbioses and recognize that cyanobacteria are the only group that has evolved the ability to carry out oxygen-producing photosynthesis 3. discuss the mechanisms of horizontal gene transfer, the widespread nature of this process in prokaryotes, and its importance in the evolution eukaryotic groups 4. describe major shapes, cell wall types, modes of nutrition used by bacteria and different responses to oxygen 5. define the following terms: halophile, extremophile, thermophile, methanogen, decomposer, nitrogen fixation, aerobic, anaerobic, photoautotroph, photoheterotroph, chemoautotroph, chemoheterotroph, transformation, transduction, conjugation, mutualism, commensalism, parasitism