Living things are divided into five kingdoms: animal, plant, fungi, protist and monera. When Carl Linnaeus was naming and classifying organisms in the 1700s, almost nothing was known of microorganisms. With the development of powerful microscopes, scientists discovered many single-celled organisms that didn't fit into any of Linnaeus' kingdoms. As a result, a new taxon, called the domain, was eventually added to the classification system. The domain is even broader than the kingdom. Biological classification now includes the domain in addition to all the taxa used by Linnaeus. ... Show more Living things are divided into five kingdoms: animal, plant, fungi, protist and monera. When Carl Linnaeus was naming and classifying organisms in the 1700s, almost nothing was known of microorganisms. With the development of powerful microscopes, scientists discovered many single-celled organisms that didn't fit into any of Linnaeus' kingdoms. As a result, a new taxon, called the domain, was eventually added to the classification system. The domain is even broader than the kingdom. Biological classification now includes the domain in addition to all the taxa used by Linnaeus. Most scientists think that all living things can be classified in three domains: Archaea, Bacteria, and Eukarya. The domains can be compared in terms of their number of cells, presence of a cell wall, and presence of a cell nucleus and other organelles. - The Archaea and Bacteria Domains contain only single-celled organisms. The Eukarya Domain contains both single-celled and multicellular organisms, but multicellular organisms are more numerous in this domain. - Both Archaea and Bacteria have cells walls, although their cell walls are made of different materials. Some Eukarya, including plants, also have cell walls. Other Eukarya, including animals, do not have cell walls. - The cells of Archaea and Bacteria lack a nucleus. A nucleus is membrane-enclosed structure for holding a cell's DNA. The cells of Archaea and Bacteria also lack other membrane-enclosed cell structures called organelles. The cells of all Eukarya, in contrast, have a nucleus and other organelles. Archaea and Bacteria may seem more similar to each other than either is to Eukarya. However, scientists think that Archaea may actually be more closely related to Eukarya than Bacteria are. This view is based on similarities in their DNA. Show less
Living things are divided into five kingdoms: animal, plant, fungi, protist and monera.
When Carl Linnaeus was naming and classifying organisms in the 1700s, almost nothing was known of microorganisms. With the development of powerful microscopes, scientists discovered many single-celled organisms that didn't fit into any of Linnaeus' kingdoms. As a result, a new taxon, called the domain, was eventually added to the classification system. The domain is even broader than the kingdom. Biological classification now includes the domain in addition to all the taxa used by Linnaeus.
Most scientists think that all living things can be classified in three domains: Archaea, Bacteria, and Eukarya. The domains can be compared in terms of their number of cells, presence of a cell wall, and presence of a cell nucleus and other organelles. - The Archaea and Bacteria Domains contain only single-celled organisms. The Eukarya Domain contains both single-celled and multicellular organisms, but multicellular organisms are more numerous in this domain. - Both Archaea and Bacteria have cells walls, although their cell walls are made of different materials. Some Eukarya, including plants, also have cell walls. Other Eukarya, including animals, do not have cell walls. - The cells of Archaea and Bacteria lack a nucleus. A nucleus is membrane-enclosed structure for holding a cell's DNA. The cells of Archaea and Bacteria also lack other membrane-enclosed cell structures called organelles. The cells of all Eukarya, in contrast, have a nucleus and other organelles. Archaea and Bacteria may seem more similar to each other than either is to Eukarya. However, scientists think that Archaea may actually be more closely related to Eukarya than Bacteria are. This view is based on similarities in their DNA.
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