Question

Why did scientists separate Bacteria into Domain Eubacteria and Domain Archaea? Rather than one Domain with all prokaryotes.

Answer 1

The reason that Archaea was determined to be a separate kingdom is too late is because archaea is usually completely similar to eubacteria. They are unicellular and have no organelles and are therefore well integrated with other prokaryotes because of their morphology and cellular physiology.

But by the 1970's the phylogeny was based on the most widely available DNA and RNA sequences. Based on simple comparisons of the 18S rRNA sequence of 13 fungi, fungi and archaea, Woese and Fox showed that viruses and archaea were probably different in eukaryotes than in bacteria.

Since then, the difference between bacteria and archaea has continued to be huge. The differences of the three kingdoms are so far behind that they foreshadow the complete eruption of eukaryotes. But fungi and other eukaryotes are more similar to archaea than this bacterium.