What characteristics have contributed to [Prokaryotes’] success at spreading to new habitats?
The extreme diversity of bacteria and archaea has driven their success in spreading to new habitats. They range morphologically as well as metabolically, allowing species to thrive in regions that are usually uninhabitable. They are found where oxygen is not present, on the ocean surface, 10,000 meters underwater, in Antarctic sea ice and in areas over 121 degrees Celsius.
Which leads into the next question…
In what ways have bacteria and archaea diversified?
Morphologically, prokaryotes vary greatly in size, shape and motility. Over a billion of the smallest known bacteria could fit inside of the largest. The shape of these organisms ranges from filaments to spheres to rods to chains and spirals. Similarly, prokaryotes may be completely immobile or may use mechanisms such as flagella, cilia or pseudopodia to move about. Cell wall composition also varies among prokaryotes. Some are Gram-positive, meaning layers of peptidoglycan serve as the outermost structure for the organism. Gram-negative cell walls, in contrast, have an additional outer phospholipid bilayer.
Metabolically, bacteria and archaea are also diverse. As posted previously, they can be chemoautotrophic, photoautotrophic, chemoheterotrophic, or photoheterotrophic. Because of this, a prokaryotic species may synthesize organic compounds themselves, or get them from other organisms. They may also synthesize ATP with sunlight or chemicals as their energy source.