Kingdoms

Before the three-domain system, the highest rank was the kingdom. The widely used five-kingdom system, proposed by Robert Whittaker in 1969, places organisms into five kingdoms based on cell structure, body organisation and type of nutrition.Prokaryotae (Monera): all prokaryotes; no nucleus or membrane-bound organelles, 70S ribosomes, circular DNA, mostly single-celled. Example: bacteria.Protoctista: eukaryotes that do not fit into the animal, plant or fungus kingdoms. Mostly single-celled; some are autotrophic (algae) and some heterotrophic. Examples: Amoeba, Paramecium, seaweeds.Fungi: eukaryotic; cell walls made of chitin; body usually made of thread-like hyphae forming a mycelium (yeasts are single-celled); store carbohydrate as glycogen. They are heterotrophic with saprotrophic nutrition: they secrete enzymes onto dead matter and absorb the products. Examples: mushrooms, moulds, yeast.Plantae: multicellular eukaryotes; cell walls made of cellulose; chloroplasts; autotrophic by photosynthesis; store carbohydrate as starch. Examples: mosses, ferns, flowering plants.Animalia: multicellular eukaryotes; no cell walls; heterotrophic, usually ingesting food; nervous coordination; store carbohydrate as glycogen. Examples: insects, fish, mammals.In the three-domain system, the kingdom Prokaryotae is split between the domains Bacteria and Archaea, and the four eukaryotic kingdoms are all placed in the domain Eukarya.