Which of the following represents the three domains of life?

The classification of life into three domains is based on fundamental genetic and biochemical differences. The correct grouping of Bacteria, Archaea, and Eukarya reflects major evolutionary branches.

Bacteria are single-celled organisms that do not have a nucleus and are characterized by their distinct cell walls and metabolic pathways. Archaea are also single-celled organisms, similar to bacteria in some aspects, but they possess unique membrane lipids and have genetic machinery more akin to eukaryotes, which allows them to thrive in extreme environments. Eukarya encompasses a wide range of organisms, including plants, animals, fungi, and protists, all of which share cells with a defined nucleus and complex cell structures.

Other groupings do not accurately represent the three domains. Protozoa, fungi, plants, and animals, while they are diverse forms of life, are all classified under eukarya and do not capture the breadth of the three domains. Viruses and parasites are not considered domains of life as viruses are not cellular and do not possess metabolic processes, while parasites, though potentially complex, fall within larger domains rather than representing a distinct domain themselves.