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A protist is any eukaryotic organism (that is, an organism whose cells contain a cell nucleus) that is not an animal, plant, or fungus.While it is likely that protists share a common ancestor, the last eukaryotic common ancestor, [1] the exclusion of other eukaryotes means that protists do not form a natural group, or clade.
The metabolism of prokaryotes is far more varied than that of eukaryotes, leading to many highly distinct prokaryotic types. For example, in addition to using photosynthesis or organic compounds for energy, as eukaryotes do, marine prokaryotes may obtain energy from inorganic compounds such as hydrogen sulfide.
Their metabolism is far more varied than that of eukaryotes, leading to many highly distinct types. For example, prokaryotes may obtain energy by chemosynthesis. [34] Prokaryotes live nearly everywhere on Earth, including in environments as cold as soils in Antarctica, [35] or as hot as undersea hydrothermal vents and land-based hot springs. [33]
A protist (/ ˈ p r oʊ t ɪ s t /) is any eukaryotic organism (one with cells containing a nucleus) that is not an animal, plant, or fungus.The protists do not form a natural group, or clade, since they exclude certain eukaryotes with whom they share a common ancestor; [a] but, like algae or invertebrates, the grouping is used for convenience.
Bacteria are prokaryotic microorganisms that can either have a bacilli, spirilli, or cocci shape and measure between 0.5-20 micrometers. They were one of the first living cells to evolve [9] and have spread to inhabit a variety of different habitats including hydrothermal vents, glacial rocks, and other organisms.
The three-domain system adds a level of classification (the domains) "above" the kingdoms present in the previously used five- or six-kingdom systems.This classification system recognizes the fundamental divide between the two prokaryotic groups, insofar as Archaea appear to be more closely related to eukaryotes than they are to other prokaryotes – bacteria-like organisms with no cell nucleus.
Another name applied to this node is Plastida, defined as the clade sharing "plastids of primary (direct prokaryote) origin [as] in Magnolia virginiana Linnaeus 1753". [ 28 ] Although many studies have suggested the Archaeplastida form a monophyletic group, [ 29 ] a 2009 paper argues that they are in fact paraphyletic . [ 23 ]
The term Monera became well established in the 20s and 30s when to rightfully increase the importance of the difference between species with a nucleus and without. In 1925, Édouard Chatton divided all living organisms into two sections, Prokaryotes and Eukaryotes: the Kingdom Monera being the sole member of the Prokaryotes section. [23]