The Kingdom Monera is comprised of bacteria . In addition, most have a cell wall consisting mostly of peptidoglycan. Reproduction is by binary fission . Some bacteria have flagella, but no microtubules. Some have filamentous structures, pili , projecting from the surface.
Metabolic diversity is much greater than for other life forms.
Most bacterial classification schemes are artificial and are constantly in a state of flux. The one most widely used is based on structural and physiological characteristics useful in identifying pathogens. Archaebacteria are believed to resemble the earliest life forms since they persist in harsh habitats which resemble conditions which probably existed when the earth was young. Thus, these bacteria allowed for the evolution of aerobic organisms. These are also important as nitrogen fixers.