Archaea and eubacteria are primarily different in their genetic and biochemical characteristics.
While both archaea and eubacteria are single-celled microorganisms, they exhibit distinct differences in their genetic makeup, cell membrane structure, and metabolic processes. Here are some primary differences between the two:
1. Genetic Makeup: Archaea have unique genetic sequences that differ from both eubacteria and eukaryotes. They possess genes and genetic machinery that are distinct from other organisms, making them a separate domain of life.
2. Cell Membrane Composition: Archaea have cell membranes composed of unique lipids called isoprenoids, which are different from the fatty acid-based lipids found in eubacteria and eukaryotes. This structural difference allows archaea to thrive in extreme environments, such as hot springs and acidic environments.
3. Metabolic Processes: Archaea exhibit diverse metabolic pathways and can utilize a wide range of energy sources, including methane, sulfur, and even sunlight. Eubacteria, on the other hand, encompasses a broader range of metabolic diversity and can be found in various environments, including soil, water, and living organisms.
Regarding the second part of your statement, archaea and eubacteria are not considered ancestors of protists and first eukaryotes. The origin of eukaryotes is still an area of scientific inquiry and debate. However, current scientific understanding suggests that eukaryotes likely evolved from a symbiotic relationship between prokaryotic cells, including both archaea and eubacteria, giving rise to complex cellular structures and internal compartments. This process is known as endosymbiotic theory. Protists, which are a diverse group of eukaryotic microorganisms, likely evolved later in the course of evolution.