In Biology, what is a Domain?
In biology, a domain is the highest possible classification of organisms. According to the modern system, called the three-domain system, created by Carl Woese in 1990, there are three domains: Eucaryota (eukaryotes), Archaea, and Bacteria. Older systems include the two-empire system — Prokaryota and Eukaryota — and the six-kingdom system — Protista, Archaebacteria, Eubacteria, Fungi, Plantae, and Animalia. Based on genetic analysis and careful argument, most scientists have agreed that the three-domain system best classifies the diversity of life. Carl Woese’s system has been praised for emphasizing microbial diversity, and recognizing fundamental differences between archaea and bacteria, enough to warrant putting them in different domains. The two-empire system is said to ignore these differences, while the six-kingdom system overemphasizes the distinctness of fungi, plants, and animals, which are all eukaryotes, made of complex cells with organelles and nuclei. All multicellular ani
