And we cannot exclude the possibility of an experimental test: it would be enough to discover in the geological record the signs of ancient seas where potassium was more abundant than sodium (such a discovery would allow us, among other things, to put a date on the RNP world and on the origin of life).
The Potassium world hypothesis is mentioned here because it has important consequences for the first stages of cellular evolution. If the hypothesis is right, we have to conclude that the ancient potassium seas gradually turned into sodium-dominated oceans, and this slow but deep transformation of the planet (comparable to the global change of the Earth’s atmosphere by the introduction of oxygen) must have had an influence on the evolution of the first cells.

Two forms of life

The greatest divide of the living world is not between plants and animals, as it has been thought for thousands of years, but between cells without a nucleus (prokaryotes) and nucleated cells (eukaryotes). Prokaryotes, or bacteria, have only one DNA molecule, arranged in a circle, a single cytoplasmic compartment where all biochemical reactions take place in solution, and normally the form of the cell is due to an external wall (an exoskeleton) that surrounds the cell’s plasmatic membrane.
Eukaryotes have various DNA molecules, arranged in linear fibers which are repeatedly coiled and folded to produce highly organized chromosomes, a composite cytoplasm which is divided into distinct compartments and houses a variety of cell organelles (mitochondria, chloroplasts, lysosomes, endoplasmic reticulum, etc.), and the form of the cell is due to an internal cytoskeleton which is made by three different types of filaments (microtubules, microfilaments and intermediate filaments).
These structural differences are but a reflection of two totally different life-styles.
Prokaryotes live almost exclusively as single cells, and can inhabit virtually any ecological niche, with or without light, with or without oxygen, with or without organic molecules.