Fossil records reflect the abundance of life. Total anaerobes bury themselves as deeply as they can in their communities. Strains of cyanobacteria, poisoned by their own oxygen waste, team up with populations of respiring bacteria which immediately slurp up the oxygen so toxic to their cousins.
Off and running in waves of innovation, aerobes' new-found energies allow them to experiment. They forge new niches, specialize and try new sorts of life styles. Some bud motile offspring who, although clones, look nothing like the parent. These baby bacteria swim to a favorable location, attach to a solid surface and "metamorphose" back into parental form.