Death

== In biology ==
[[File:Earthworm.jpg|thumb|[[Earthworm]]s are soil-dwelling detritivores.]]

After death, the remains of a former organism become part of the [[biogeochemical cycle]], during which animals may be [[necrophagy|consumed]] by a [[predator]] or a [[scavenger]].<ref>{{Citation |last=Falkowski |first=Paul G. |title=Biogeochemical Cycles |date=2001-01-01 |url=https://www.sciencedirect.com/science/article/pii/B0122268652000328 |encyclopedia=Encyclopedia of Biodiversity |pages=437–453 |editor-last=Levin |editor-first=Simon Asher |place=New York |publisher=Elsevier |language=en |doi=10.1016/b0-12-226865-2/00032-8 |isbn=978-0-12-226865-6 |access-date=2022-08-23 |archive-date=9 February 2023 |archive-url=https://web.archive.org/web/20230209233608/https://www.sciencedirect.com/science/article/pii/B0122268652000328 |url-status=live }}</ref> [[Organic material]] may then be further decomposed by [[detritivore]]s, organisms that recycle [[detritus]], returning it to the environment for reuse in the [[food chain]], where these chemicals may eventually end up being consumed and assimilated into the cells of an organism.<ref>{{Cite book |last=Wetzel |first=Robert |title=Limnology: Lake and River Ecosystems |date= 2001 |publisher=Elsevierda |isbn=978-0-12-744760-5 |edition=3rd |page=700}}</ref> Examples of detritivores include [[earthworm]]s, [[woodlice]], and [[millipede]]s.<ref>{{Cite journal |last1=Lindsey-Robbins |first1=Josephine |last2=Vázquez-Ortega |first2=Angélica |last3=McCluney |first3=Kevin |last4=Pelini |first4=Shannon |date=December 13, 2019 |title=Effects of Detritivores on Nutrient Dynamics and Corn Biomass in Mesocosms |journal=Insects |volume=10 |issue=12 |page=453 |doi=10.3390/insects10120453 |pmid=31847249 |pmc=6955738 |doi-access=free }}</ref>

[[Microorganism]]s also play a vital role, raising the temperature of the decomposing matter as they break it down into yet simpler molecules.<ref>{{Cite journal |last1=Rousk |first1=Johannes |last2=Bengston |first2=Per |date=March 14, 2014 |title=Microbial regulation of global biogeochemical cycles |journal=Frontiers in Microbiology |volume=5 |page=103 |doi=10.3389/fmicb.2014.00103 |pmid=24672519 |pmc=3954078 |doi-access=free }}</ref> Not all materials need to be fully decomposed. Coal, a [[fossil fuel]] formed over vast tracts of time in [[swamp]] ecosystems, is one example.<ref>{{Cite book |last=George |first=McGhee |title=Carboniferous Giants and Mass Extinction: The Late Paleozoic Ice Age World |publisher=Columbia University Press |year=2018 |isbn=978-0-231-18097-9 |pages=98–102}}</ref>

=== Natural selection ===
{{Main|Competition (biology)|Natural selection}}

The contemporary [[history of evolutionary thought|evolutionary theory]] sees death as an important part of the process of [[natural selection]]. It is considered that organisms less [[adaptation|adapted]] to their environment are more likely to die, having produced fewer offspring, thereby reducing their contribution to the [[gene pool]]. Their genes are thus eventually bred out of a population, leading at worst to [[extinction]] and, more positively, making the process possible, referred to as [[speciation]]. Frequency of [[biological reproduction|reproduction]] plays an equally important role in determining species survival: an organism that dies young but leaves numerous offspring displays, according to [[Charles Darwin|Darwinian]] criteria, much greater [[Darwinian fitness|fitness]] than a long-lived organism leaving only one.<ref>{{Cite journal |last=Gregory |first=T. Ryan |date=June 2009 |title=Understanding Natural Selection: Essential Concepts and Common Misconceptions |journal=Evolution: Education and Outreach |language=en |volume=2 |issue=2 |pages=156–175 |doi=10.1007/s12052-009-0128-1 |doi-access=free |issn=1936-6434 |s2cid=4508223}}</ref><ref>{{Cite journal |last=Haldane |first=J. B. S. |author-link=J. B. S. Haldane |date=December 1957 |title=The cost of natural selection |url=https://link.springer.com/article/10.1007/BF02984069 |journal=[[Journal of Genetics]] |volume=55 |issue=3 |pages=511–524 |doi=10.1007/BF02984069 |s2cid=32233460 |via=SpringerLink |access-date=16 February 2023 |archive-date=17 August 2023 |archive-url=https://web.archive.org/web/20230817195526/https://link.springer.com/article/10.1007/BF02984069 |url-status=live }}</ref>

Death also has a role in [[Competition (biology)|competition]], where if a species out-competes another, there is a risk of death for the population, especially in the case where they are directly fighting over resources.<ref>{{Cite journal |last1=Case |first1=Ted J. |last2=Gilpin |first2=Micheal E. |date=August 1, 1974 |title=Interference Competition and Niche Theory |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=71 |issue=8 |pages=3073–3077 |bibcode=1974PNAS...71.3073C |doi=10.1073/pnas.71.8.3073 |issn=0027-8424 |pmc=388623 |pmid=4528606 |doi-access=free}}</ref>

=== Extinction ===
{{Main|Extinction}}
[[File:ExtinctDodoBird.jpeg|thumb|upright|alt=Painting of a dodo|A [[dodo]], the bird that became a [[byword (saying)|byword]] in the English language for the extinction of a species<ref name="Diamond">{{cite book|last=Diamond |first=Jared M. |author-link=Jared Diamond |title=Guns, Germs, and Steel: The Fates of Human Societies |edition=illustrated, reprint |publisher=[[W.W. Norton]] |year=1999 |isbn=978-0-393-31755-8 |pages=[https://archive.org/details/gunsgermssteelfa00diam/page/43 43–44] |chapter=Up to the Starting Line|title-link=Guns, Germs, and Steel }}</ref>]]

Death plays a role in [[extinction]], the cessation of existence of a species or group of [[Taxon|taxa]], reducing [[biodiversity]], due to extinction being generally considered to be the death of the last individual of that species (although the [[population bottleneck|capacity to breed and recover]] may have been lost before this point). Because a species' potential [[range (biology)|range]] may be very large, determining this moment is difficult, and is usually done retrospectively.<ref>{{Cite journal |last1=Purvis |first1=Andy |last2=Jones |first2=Kate E. |last3=Mace |first3=Georgina M. |date=November 10, 2000 |title=Extinction |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/1521-1878(200012)22:12%3C1123::AID-BIES10%3E3.0.CO;2-C |journal=[[BioEssays]] |volume=22 |issue=12 |pages=1123–1133 |doi=10.1002/1521-1878(200012)22:12<1123::AID-BIES10>3.0.CO;2-C |pmid=11084628 |s2cid=221463059 |via=Wiley Online Library |access-date=16 February 2023 |archive-date=16 February 2023 |archive-url=https://web.archive.org/web/20230216194700/https://onlinelibrary.wiley.com/doi/abs/10.1002/1521-1878(200012)22:12%3C1123::AID-BIES10%3E3.0.CO;2-C |url-status=live }}</ref>

=== Evolution of aging and mortality ===
{{Main|Evolution of ageing}}

Inquiry into the evolution of aging aims to explain why so many living things and the vast majority of animals weaken and die with age. However, there are exceptions, such as ''[[Hydra (genus)|Hydra]]'' and the jellyfish ''[[Turritopsis dohrnii]]'', which research shows to be [[biological immortality|biologically immortal]].<ref>{{Cite web |last=National Institute on Aging |date=2020 |title=The National Institute on Aging: Strategic Directions for Research, 2020–2025 |url=https://www.nia.nih.gov/about/aging-strategic-directions-research |access-date=February 16, 2023 |website=National Institute on Aging |archive-date=4 June 2020 |archive-url=https://web.archive.org/web/20200604212742/https://www.nia.nih.gov/about/aging-strategic-directions-research |url-status=live }}</ref>

Organisms showing only [[asexual reproduction]], such as bacteria, some [[protist]]s, like the [[euglenoid]]s and many [[amoebozoan]]s, and [[unicellular]] organisms with [[sexual reproduction]], [[Colony (biology)|colonial]] or not, like the [[Volvocales|volvocine]] algae ''[[Pandorina]]'' and ''[[Chlamydomonas]],'' are "immortal" at some extent, dying only due to external hazards, like being eaten or meeting with a fatal accident. In [[multicellular]] organisms and also in [[multinucleate]] [[ciliates]]<ref>Beukeboom, L. & Perrin, N. (2014). ''The Evolution of Sex Determination''. Online Chapter 2: [http://global.oup.com/booksites/content/9780199657148/ The diversity of sexual cycles] {{Webarchive|url=https://web.archive.org/web/20141112034751/http://global.oup.com/booksites/content/9780199657148/ |date=12 November 2014 }}, p. 12. Oxford University Press.</ref> with a [[Weismann barrier|Weismannist development]], that is, with a division of labor between mortal [[somatic cells|somatic (body) cells]] and "immortal" [[germ cell|germ (reproductive) cells]], death becomes an essential part of life, at least for the somatic line.<ref name=Gilbert>{{cite book|last=Gilbert |first=S.F. |year=2003 |title=Developmental biology |edition=7th |place=Sunderland, Mass |publisher=Sinauer Associates |pages=34–35 |isbn=978-0-87893-258-0}}</ref>

The ''[[Volvox]]'' algae are among the simplest organisms to exhibit that division of labor between two completely different cell types, and as a consequence, include the death of somatic line as a regular, genetically regulated part of its [[Biological life cycle|life history]].<ref name=Gilbert /><ref>{{cite journal|doi=10.1007/s00497-010-0158-4 |pmid=21174128 |pmc=3098969 |title=Evolution of reproductive development in the volvocine algae |last=Hallmann |first=A. |journal=Sexual Plant Reproduction |date=June 2011 |volume=24 |issue=2 |pages=97–112}}</ref>

=== Grief in animals ===
Animals have sometimes shown grief for their partners or "friends." When two [[chimpanzee]]s form a bond together, [[Intimate relationship|sexual]] or [[Platonic love|not]], and one of them dies, the surviving chimpanzee will show signs of grief, ripping out their hair in anger and starting to cry; if the body is removed, they will resist, they will eventually go quiet when the body is gone, but upon seeing the body again, the chimp will return to a violent state.<ref>{{Cite journal |last=Brown |first=Arthur E. |date=March 1879 |title=Grief in the Chimpanzee |journal=The American Naturalist |volume=13 |issue=3 |pages=173–175 |doi=10.1086/272298 |jstor=2448772 |jstor-access=free}}</ref>

=== Death of abiotic factors ===
Some [[Abiotic component|non-living]] things can be considered dead. For example, a [[volcano]], batteries, electrical components, and stars are all nonliving things that can "die," whether from destruction or cessation of function.

A [[volcano]], a break in the earth's crust that allows [[lava]], [[Pyroclastic flow|ash, and gases]] to escape, has three states that it may be in, active, dormant, and extinct. An [[active volcano]] has recently or is currently [[Erupting volcano|erupting]]; in a [[dormant volcano]], it has not erupted for a significant amount of time, but it may erupt again; in an extinct volcano, it may be cut off from the supply of its lava and will never expected to erupt again, so the volcano can be considered to be dead.<ref>{{Cite web |title=Volcanoes |url=https://education.nationalgeographic.org/resource/volcanoes/ |access-date=2023-02-17 |website=education.nationalgeographic.org |language=en |archive-date=26 May 2022 |archive-url=https://web.archive.org/web/20220526020944/https://education.nationalgeographic.org/resource/volcanoes |url-status=live }}</ref>

A [[Electric battery|battery]] can be considered dead after the charge is fully used up. [[Electronic component|Electrical components]] are similar in this fashion, in the case that it may not be able to be used again, such as after a spill of water on the components,<ref>{{Cite journal |last1=Baylakoğlu |first1=İlknur |last2=Fortier |first2=Aleksandra |last3=Kyeong |first3=San |last4=Ambat |first4=Rajan |last5=Conseil-Gudla |first5=Helene |last6=Azarian |first6=Michael H. |last7=Pecht |first7=Michael G. |date=October 28, 2021 |title=The detrimental effects of water on electronic devices |journal=E-Prime – Advances in Electrical Engineering, Electronics and Energy. |volume=1 |issue=10 |page=1016 |doi=10.1016/j.prime.2021.100016 |s2cid=245746859 |issn=2772-6711 |doi-access=free }}</ref> the component can be considered dead.

[[File:Keplers supernova.jpg|thumb|[[Kepler's Supernova]], after the death of what could have been a [[white dwarf]]]]

Stars also have a life-span and, therefore, can die. After it starts to run out of fuel, it starts to expand, this can be analogous to the star aging. After it exhausts all fuel, it may explode in a [[supernova]],<ref>{{Cite journal |last=Croswell |first=Ken |date=2020-01-21 |title=A massive star dies without a bang, revealing the sensitive nature of supernovae |journal=Proceedings of the National Academy of Sciences |language=en |volume=117 |issue=3 |pages=1240–1242 |doi=10.1073/pnas.1920319116 |issn=0027-8424 |pmc=6983415 |pmid=31964780|doi-access=free }}</ref> collapse into a [[black hole]], or turn into a [[neutron star]].<ref>{{Cite journal |last1=Heger |first1=A. |last2=Fryer |first2=C. L. |last3=Woosley |first3=S. E. |last4=Langer |first4=N. |last5=Hartmann |first5=D. H. |date=July 2003 |title=How Massive Single Stars End Their Life |url=https://iopscience.iop.org/article/10.1086/375341 |journal=The Astrophysical Journal |language=en |volume=591 |issue=1 |pages=288–300 |doi=10.1086/375341 |arxiv=astro-ph/0212469 |bibcode=2003ApJ...591..288H |s2cid=15539500 |issn=0004-637X |access-date=21 February 2023 |archive-date=20 July 2023 |archive-url=https://web.archive.org/web/20230720110657/https://iopscience.iop.org/article/10.1086/375341 |url-status=live }}</ref>