Final answer:
The old Kingdom Monera was divided into Bacteria and Archaebacteria because of significant differences in cell membrane structure and ribosomal RNA, revealing that they are as different from each other as from Eukarya.
Step-by-step explanation:
Division of the Old Prokaryotic Kingdom Monera
The old prokaryotic Kingdom Monera was divided into the two new domains of Bacteria and Archaebacteria due to significant differences in cell membrane structure and genetic material, specifically ribosomal RNA (rRNA). Both domains comprise prokaryotic cells, which lack nuclei and true membrane-bound organelles. However, extensive molecular analysis, including the comparison of small-subunit rRNA sequences, revealed that the organisms within these two groups have fundamental genetic differences. Notably, Archaea share more traits with the Eukarya domain, indicating a more recent common ancestry. These findings led to the reclassification of life into three domains: Bacteria, Archaea, and Eukarya, where Archaea and Bacteria differ as much from each other as they do from eukaryotic organisms. This reclassification reflects our evolving understanding of the diversity and evolutionary history of life on Earth.