An organism (from Ancient Greek ὄργανον (órganon) 'instrument, implement, tool', and Ancient Greek -ισμός (-ismós)) is any biological living system that functions as an individual life form.[1] All organisms are composed of cells.[1] The idea of organism is based on the concept of minimal functional unit of life. Three traits have been proposed to play the main role in qualification as an organism:
Organisms include multicellular animals, plants, and fungi; or unicellular microorganisms such as protists, bacteria, and archaea.[5] All types of organisms are capable of reproduction, growth and development, maintenance, and some degree of response to stimuli. Most multicellular organisms differentiate into specialized tissues and organs during their development.
In 2016, a set of 355 genes from the last universal common ancestor (LUCA) of all organisms from Earth was identified.