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  2. Biological organisation - Wikipedia

    en.wikipedia.org/wiki/Biological_organisation

    For levels larger than Biosphere or Ecosphere, see Earth's location in the Universe More complex schemes incorporate many more levels. For example, a molecule can be viewed as a grouping of elements , and an atom can be further divided into subatomic particles (these levels are outside the scope of biological organisation).

  3. Domain (biology) - Wikipedia

    en.wikipedia.org/wiki/Domain_(biology)

    Halophiles (organisms that thrive in highly salty environments) and hyperthermophiles (organisms that thrive in extremely hot environments) are examples of Archaea. [1] Archaea are relatively small. They range from 0.1 μm to 15 μm diameter and up to 200 μm long, about the size of bacteria and the mitochondria found in eukaryotic cells.

  4. Two-domain system - Wikipedia

    en.wikipedia.org/wiki/Two-domain_system

    The two-domain system is a biological classification by which all organisms in the tree of life are classified into two domains, Bacteria and Archaea. [ 1 ] [ 2 ] [ 3 ] It emerged from development of knowledge of archaea diversity and challenges the widely accepted three-domain system that classifies life into Bacteria, Archaea, and Eukarya . [ 4 ]

  5. Organism - Wikipedia

    en.wikipedia.org/wiki/Organism

    Differing levels of biological organisation give rise to potentially different understandings of the nature of organisms. A unicellular organism is a microorganism such as a protist , bacterium , or archaean , composed of a single cell , which may contain functional structures called organelles . [ 22 ]

  6. Kingdom (biology) - Wikipedia

    en.wikipedia.org/wiki/Kingdom_(biology)

    The kingdom-level classification of life is still widely employed as a useful way of grouping organisms, notwithstanding some problems with this approach: Kingdoms such as Protozoa represent grades rather than clades , and so are rejected by phylogenetic classification systems.

  7. Taxonomic rank - Wikipedia

    en.wikipedia.org/wiki/Taxonomic_rank

    A taxon is usually assigned a rank when it is given its formal name. The basic ranks are species and genus. When an organism is given a species name it is assigned to a genus, and the genus name is part of the species name. The species name is also called a binomial, that is, a two-term name.

  8. Three-domain system - Wikipedia

    en.wikipedia.org/wiki/Three-domain_system

    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.

  9. Living systems - Wikipedia

    en.wikipedia.org/wiki/Living_systems

    Below the level of living systems, he defines space and time, matter and energy, information and entropy, levels of organization, and physical and conceptual factors, and above living systems ecological, planetary and solar systems, galaxies, etc. [3] [4] [5] Miller's central thesis is that the multiple levels of living systems (cells, organs ...