What Are The Similarities Of Viruses, Bacteria, And Archaea?

1. The first similarity is that they all contain genetic material (.i.e. DNA or even RNA in case of Viruses.
2. All viruses are pathogenic, i.e. they cause diseases. Some Bacteria and Archae (archaebacteria) are also pathogenic.
3. They all have protective coverings; in case of viruses the covering is a protein coat called Capsid. Bacteria and Archae (Archaebactetia) have two protective coverings, cell membrane and cell wall. Cell membrane is made up of phospho-lipid bilayer and cell wall is made up of petidoglycan, cellulose, pectin, hemicellulose and sometimes lignin.
4. They have all evolved before multicellular organisms. No doubt Viruses don’t have cellular structure but they have evolved before other higher organisms like Bacteria and Archae.
5. They are nearly immortal because they all multiple and increase their numbers without perishing.
6. All the three can not be seen with the naked eyes. Bacteria and Archae can be seen under light microscope and viruses can only be seen under Electron Microscope or Scanning Electron Microscope.
7. All of them are very populous and nearly innumerable.