Temporal range: ArcheanPresent (possible Hadean origin)
Diversidad procariota.PNG
Diversity of Prokaryota which includes Archaea, Cyanobacteria, Bacillus, Campylobacteria, Enterobacteria, Diplococcus, and Spirochete
Eukaryota diversity 1.JPG
Diversity of Eukaryota which includes Gray wolf, Giant sequoia, Entodinium, Amanita caesarea, Pterois antennata, Algae blooms, Chrysotoxum verralli, Xanthoparmelia lichen, Dictyostelium, and Pillar coral
Scientific classification e
Domains and Supergroups

Life on Earth:

Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from matter that does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energy transformation, and reproduction.[2][3] Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria. Biology is the science that studies life.

The gene is the unit of heredity, whereas the cell is the structural and functional unit of life.[4][5] There are two kinds of cells, prokaryotic and eukaryotic, both of which consist of cytoplasm enclosed within a membrane and contain many biomolecules such as proteins and nucleic acids. Cells reproduce through a process of cell division, in which the parent cell divides into two or more daughter cells and passes its genes onto a new generation, sometimes producing genetic variation.

Organisms, or the individual entities of life, are generally thought to be open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to stimuli, reproduce and evolve over multiple generations. Other definitions sometimes include non-cellular life forms such as viruses and viroids, but they are usually excluded because they do not function on their own; rather, they exploit the biological processes of hosts.[6][7]

Abiogenesis, also known as the origin of life, is the natural process of life arising from non-living matter, such as simple organic compounds. Since its primordial beginnings, life on Earth has changed its environment on a geologic time scale, but it has also adapted to survive in most ecosystems and conditions. New lifeforms have evolved from common ancestors through hereditary variation and natural selection, and today, estimates of the number of distinct species range anywhere from 3 million to over 100 million.[3][8]

Death is the permanent termination of all biological processes which sustain an organism, and as such, is the end of its life. Extinction is the term describing the dying-out of a group or taxon, usually a species. Once extinct, the extinct species or taxon cannot come back to life. Fossils are the preserved remains or traces of organisms.

Cite error: There are <ref group=note> tags on this page, but the references will not show without a {{reflist|group=note}} template (see the help page).

  1. ^ International Committee on Taxonomy of Viruses Executive Committee (May 2020). "The New Scope of Virus Taxonomy: Partitioning the Virosphere Into 15 Hierarchical Ranks". Nat Microbiol. 5 (5): 668–674. doi:10.1038/s41564-020-0709-x. PMC 7186216. PMID 32341570.
  2. ^ Cite error: The named reference merriamwebster was invoked but never defined (see the help page).
  3. ^ a b "life | Definition, Origin, Evolution, Diversity, & Facts". Encyclopedia Britannica. Archived from the original on 12 July 2022. Retrieved 25 July 2022.
  4. ^ "2.2: The Basic Structural and Functional Unit of Life: The Cell". LibreTexts. 2 June 2019. Archived from the original on 29 March 2020. Retrieved 29 March 2020.
  5. ^ Bose, Debopriya (14 May 2019). "Six Main Cell Functions". Leaf Group Ltd./Leaf Group Media. Archived from the original on 29 March 2020. Retrieved 29 March 2020.
  6. ^ "Virus". Archived from the original on 11 May 2022. Retrieved 25 July 2022.
  7. ^ "Are Viruses Alive?". Yellowstone Thermal Viruses. Archived from the original on 14 June 2022. Retrieved 25 July 2022.
  8. ^ "How Many Species Exist?". National Wildlife Federation. Archived from the original on 25 July 2022. Retrieved 25 July 2022.

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