Which group of organisms evolved before eukaryotes?

Bacteria and Archaea are the correct answer because they represent the earliest forms of life on Earth, emerging long before eukaryotes. Eukaryotes are defined by having complex cells with membrane-bound organelles, including a nucleus. In contrast, bacteria and archaea are prokaryotic organisms, which are simpler and lack these structures.

The evolutionary timeline supports this; prokaryotes, particularly bacteria, are among the first organisms to have appeared, with evidence dating back around 3.5 billion years. Archaea, while also prokaryotic, share a more recent common ancestor with eukaryotes than bacteria do, but both groups predate the emergence of eukaryotic life forms, which arose approximately 1.5 to 2 billion years ago.

Other options listed include organisms that are all eukaryotic. Protists and fungi, as well as plants and animals, evolved from ancestral eukaryotic lineages and therefore originated well after bacteria and archaea. Viruses and prions, while they can influence the evolution of living organisms, are not classified within the Tree of Life as they do not have cellular structures and are not considered living organisms in the same way. Thus,