Classification of Organisms
Taken from an entry in MSN Encarta, which has closed down
Greek philosopher Aristotle (384 - 322 BC) grouped life forms as either plant or animal. Microscopic organisms were unknown.
| Plants | Animals | |
| Plants | Animals | |
| Fungi |
In 1735 Swedish naturalist Carolus Linnaeus formalised the use of two Latin names to identify each organism, a system called binomial nomenclature. He grouped closely related organisms and introduced the modern classification groups: kingdom, pylum, class, order, family, genus, and species. Single-celled organisms were observed but not classified.
| Kingdom: | Plantae | Animalia | ||
| Organisms | Plants | Animals | ||
| Fungi |
In 1866 German biologist Ernst Haeckel proposed a third kingdom, Protista, to include all single-celled organisms. Some taxonomists also placed simple multicellular, such as seaweeds, in Kingdom Protista. Bacteria, which lack nuclei, were placed in a separate group within Protista called Monera.
| Kingdom: | Protista | Plantae | Animalia |
| Organisms: | All single-celled organisms, such as amoebas and diatoms, and sometimes simple multicellular organisms such as seaweeds. | Plants | Animals |
In 1938 American biologist Herbert Copeland proposed a fourth kingdom, Monera, to include only bacteria. This was the first classification proposal to separate organisms without nuclei, called prokaryotes, from organisms with nuclei, called eukaryotes, at the kingdom level.
| PROKARYOTES: | EUKARYOTES: | |||
| Kingdom: | Monera (Prokaryote) | Protista | Plantae | Animalia |
| Organisms | Bacteria | Amoebas,diatoms and other single-celled eukaryotes, and sometimes simple multicellular organisms, such as seaweeds. | Plants Fungi | Animals |
In 1957 American biologist Robert H. Whittaker proposed a fifth kingdom, Fungi, based on fungi's unique structure and method of obtaining food. Fungi do not ingest food as animals do, nor do they make their own food, as plants do; rather, they sectrete digestive enzymes around their food and absorb it into their cells.
| Kingdom | Monera (Prokaryote) | Protista | Fungi | Plantae | Animalia |
| Organisms | Bacteria | Amoebas, diatoms and other single-celled eukaryotes and sometimes simple multicellular organisms, such as seaweeds. | Multicellular filamentous organisms that absorb food. | Multicellular organisms that obtain food through photosysnthesis. | Multicellular organisms that ingest food. |
In 1990 American molecular biologist Carl Woese proposed a new category, called a Domain, to reflect evidence from nucleic acid studies that more precisely reveal evolutionary, or family, relationships. he suggested three domains, Archaea, Bacteria, and Eucarya, based largely on the type of ribonucleic acid (RNA) in cells.
| PROKARYOTES | EUKARYOTES | ||||||
| Domain: | Archaea | Bacteria | Eucarya | ||||
| Kingdom | Crenarchaeota | Euryachaeota | Protista | Fungi | Plantae | Animalia | |
| Organisms | Ancient bacteria that produce methane | Ancient bacteria that grow in high temperatures | |||||
See also: Proposal for domains Archae, Bacteria, and Eucarya
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