Editing Acclimatization

{{Short description|Biological adjustment to new climates}}
{{Distinguish|Acclamation}}
{{use mdy dates|date=September 2021}}
{{Use American English|date = March 2019}}

'''Acclimatization''' [[American and British English spelling differences#iseize|or]] '''acclimatisation''' ([[#Names|also called]] '''acclimation''' or '''acclimatation''') is the process in which an individual [[organism]] adjusts to a [[environmental change|change in its environment]] (such as a change in altitude, temperature, humidity, [[photoperiod]], or [[pH]]), allowing it to maintain [[Fitness (biology)|fitness]] across a range of environmental conditions. Acclimatization occurs in a short period of time (hours to weeks), and within the organism's lifetime (compared to [[adaptation]], which is evolution, taking place over many generations). This may be a discrete occurrence (for example, when [[mountaineering|mountaineers]] acclimate to [[altitude#High altitude and low pressure|high altitude]] over hours or days) or may instead represent part of a periodic cycle, such as a [[mammal]] shedding heavy winter [[fur]] in favor of a lighter summer coat. Organisms can adjust their morphological, behavioral, physical, and/or biochemical traits in response to changes in their environment.<ref>(2009) “Acclimatisation” (n.d.) The Unabridged Hutchinson Encyclopedia Retrieved November 5, 2009 from http://encyclopedia.farlex.com/acclimatization</ref> While the capacity to acclimate to novel environments has been well documented in thousands of species, researchers still know very little about how and why organisms acclimate the way that they do.

==Names==
The nouns ''[[wikt:acclimatization#Noun|acclimatization]]'' and ''[[wikt:acclimation#Noun|acclimation]]'' (and the corresponding verbs ''[[wikt:acclimatize#Verb|acclimatize]]'' and ''[[wikt:acclimate#Verb|acclimate]]'') are widely regarded as [[synonym]]ous,<ref name="OxfordDictionaries">{{Citation |author=Oxford Dictionaries |author-link=OxfordDictionaries.com |title=Oxford Dictionaries Online |publisher=Oxford University Press |url=http://www.oxforddictionaries.com/ |archive-url=https://web.archive.org/web/20010516042450/http://www.oxforddictionaries.com/ |url-status=dead |archive-date=May 16, 2001 |postscript=.}}</ref><ref name="MW_Collegiate">{{Citation |author=Merriam-Webster |author-link=Merriam-Webster |title=Merriam-Webster's Collegiate Dictionary |publisher=Merriam-Webster |url=http://unabridged.merriam-webster.com/collegiate/ |postscript=. |access-date=January 31, 2017 |archive-date=October 10, 2020 |archive-url=https://web.archive.org/web/20201010163505/https://unabridged.merriam-webster.com/subscriber/login?redirect_to=%2Fcollegiate%2F |url-status=dead }}</ref><ref name="MWU">{{Citation |author=Merriam-Webster |author-link=Merriam-Webster |title=Merriam-Webster's Unabridged Dictionary |publisher=Merriam-Webster |url=http://unabridged.merriam-webster.com/unabridged/ |postscript=. |access-date=January 31, 2017 |archive-date=May 25, 2020 |archive-url=https://web.archive.org/web/20200525084504/https://unabridged.merriam-webster.com/subscriber/login?redirect_to=%2Funabridged%2F |url-status=dead }}</ref><ref name="AHD">{{Citation |author=Houghton Mifflin Harcourt |title=The American Heritage Dictionary of the English Language |publisher=Houghton Mifflin Harcourt |url=https://ahdictionary.com/ |postscript=. |access-date=2017-01-31 |archive-url=https://web.archive.org/web/20150925104737/https://ahdictionary.com/ |archive-date=2015-09-25 |url-status=dead }}</ref><ref name="Dorlands">{{Citation |author=Elsevier |author-link=Elsevier |title=Dorland's Illustrated Medical Dictionary |publisher=Elsevier |url=http://dorlands.com/ |postscript=.}}</ref><ref name="Stedmans">{{Citation |author=Wolters Kluwer |author-link=Wolters Kluwer |title=Stedman's Medical Dictionary |publisher=Wolters Kluwer |url=http://stedmansonline.com/ |postscript=.}}</ref> both in general vocabulary<ref name="OxfordDictionaries"/><ref name="MW_Collegiate"/><ref name="MWU"/><ref name="AHD"/> and in medical vocabulary.<ref name="Dorlands"/><ref name="Stedmans"/> The synonym ''[[wikt:acclimation#Noun|acclimation]]''<ref name="MWU"/><ref name="Dorlands"/> is less commonly encountered, and fewer dictionaries enter it.

==Methods==
===Biochemical===
In order to maintain performance across a range of environmental conditions, there are several strategies organisms use to acclimate. In response to changes in temperature, organisms can change the biochemistry of [[cell membrane]]s making them more fluid in cold temperatures and less fluid in warm temperatures by increasing the number of [[membrane protein]]s.<ref name="Los">{{cite journal | author = Los D.A., Murata N. | year = 2004 | title = Membrane fluidity and its roles in the perception of environmental signals | journal =  Biochimica et Biophysica Acta (BBA) - Biomembranes| volume = 0666 | issue = 1–2| pages = 142–157 | doi = 10.1016/j.bbamem.2004.08.002 | pmid = 15519313 | doi-access =  }}</ref> In response to certain stressors, some organisms express so-called [[heat shock protein]]s that act as [[Chaperone (protein)|molecular chaperones]] and reduce [[Denaturation (biochemistry)|denaturation]] by guiding the [[Protein folding|folding]] and refolding of proteins. It has been shown that organisms which are acclimated to high or low temperatures display relatively high resting levels of heat shock proteins so that when they are exposed to even more extreme temperatures the proteins are readily available. Expression of heat shock proteins and regulation of membrane fluidity are just two of many biochemical methods organisms use to acclimate to novel environments.

===Morphological===
Organisms are able to change several characteristics relating to their [[morphology (biology)|morphology]] in order to maintain performance in novel environments. For example, birds often increase their organ size to increase their metabolism. This can take the form of an increase in the mass of nutritional organs or heat-producing organs, like the pectorals (with the latter being more consistent across species<ref name="LiknesSwanson2011">{{cite journal|last1=Liknes|first1=Eric T.|last2=Swanson|first2=David L.|title=Phenotypic flexibility of body composition associated with seasonal acclimatization in passerine birds|journal=Journal of Thermal Biology|volume=36|issue=6|year=2011|pages=363–370|issn=0306-4565|doi=10.1016/j.jtherbio.2011.06.010}}</ref>).<ref name="McKechnie2008">{{cite journal|last1=McKechnie|first1=Andrew E.|title=Phenotypic flexibility in basal metabolic rate and the changing view of avian physiological diversity: a review|journal=Journal of Comparative Physiology B|volume=178|issue=3|year=2008|pages=235–247|issn=0174-1578|doi=10.1007/s00360-007-0218-8|pmid=17957373|s2cid=28481792}}</ref>

==The theory==
While the capacity for acclimatization has been documented in thousands of species, researchers still know very little about how and why organisms acclimate in the way that they do. Since researchers first began to study acclimation, the overwhelming hypothesis has been that all acclimation serves to enhance the performance of the organism. This idea has come to be known as the [[beneficial acclimation hypothesis]]. Despite such widespread support for the beneficial acclimation hypothesis, not all studies show that acclimation always serves to enhance performance (''See [[beneficial acclimation hypothesis]]''). One of the major objections to the beneficial acclimation hypothesis is that it assumes that there are no costs associated with acclimation.<ref name = "Angilletta">Angilletta, M.J. (2009). Thermal Adaptation: A Theoretical and Empirical Synthesis. Oxford University Press, Oxford.</ref> However, there are likely to be costs associated with acclimation. These include the cost of sensing the environmental conditions and regulating responses, producing structures required for plasticity (such as the energetic costs in expressing [[heat shock protein]]s), and genetic costs (such as linkage of plasticity-related genes with harmful genes).<ref>{{Cite journal|last1=DeWitt|first1=Thomas J.|last2=Sih|first2=Andrew|last3=Wilson|first3=David Sloan|date=1998-02-01|title=Costs and limits of phenotypic plasticity|journal=Trends in Ecology & Evolution|volume=13|issue=2|pages=77–81|doi=10.1016/S0169-5347(97)01274-3|pmid=21238209}}</ref>

Given the shortcomings of the beneficial acclimation hypothesis, researchers are continuing to search for a theory that will be supported by empirical data.

The degree to which organisms are able to acclimate is dictated by their [[phenotypic plasticity]] or the ability of an organism to change certain traits. Recent research in the study of acclimation capacity has focused more heavily on the evolution of phenotypic plasticity rather than acclimation responses. Scientists believe that when they understand more about how organisms evolved the capacity to acclimate, they will better understand acclimation.

==Examples==

=== Plants ===
Many plants, such as [[maple tree]]s, [[iris (plant)|irises]], and [[tomato]]es, can survive freezing temperatures if the temperature gradually drops lower and lower each night over a period of days or weeks. The same drop might kill them if it occurred suddenly. Studies have shown that tomato plants that were acclimated to higher temperature over several days were more efficient at photosynthesis at relatively high temperatures than were plants that were not allowed to acclimate.<ref name = "Camejo">{{cite journal | last1=Camejo | first1=Daymi | last2=Martí | first2=María del C. | last3=Nicolás | first3=Emilio | last4=Alarcón | first4=Juan J. | last5=Jiménez | first5=Ana | last6=Sevilla | first6=Francisca | title=Response of superoxide dismutase isoenzymes in tomato plants (Lycopersicon esculentum) during thermo-acclimation of the photosynthetic apparatus | journal=Physiologia Plantarum | publisher=Wiley | volume=131 | issue=3 | year=2007 | issn=0031-9317 | doi=10.1111/j.1399-3054.2007.00953.x | pages=367–377 | pmid = 18251876}}</ref>

In the orchid ''[[Phalaenopsis]]'', [[phenylpropanoid biosynthesis|phenylpropanoid enzyme]]s are enhanced in the process of plant acclimatisation at different levels of [[photosynthesis|photosynthetic]] photon flux.<ref>{{cite journal | last1=Ali | first1=Mohammad Babar | last2=Khatun | first2=Serida | last3=Hahn | first3=Eun-Joo | last4=Paek | first4=Kee-Yoeup | title=Enhancement of phenylpropanoid enzymes and lignin in Phalaenopsis orchid and their influence on plant acclimatisation at different levels of photosynthetic photon flux | journal=Plant Growth Regulation | publisher=Springer Science and Business Media LLC | volume=49 | issue=2–3 | date=2006-09-29 | issn=0167-6903 | doi=10.1007/s10725-006-9003-z | pages=137–146| s2cid=26821483 }}</ref>

===Animals===
{{Disputed section|date=August 2011}}
Animals acclimatize in many ways. [[Sheep]] grow very thick [[wool]] in cold, damp climates. [[Fish]] are able to adjust only gradually to changes in water temperature and quality. Tropical fish sold at [[pet store]]s are often kept in [[acclimatization bags]] until this process is complete.<ref>{{Cite web | url=http://www.cpp.edu/~jskoga/Aquariums/Acclimation.html |title = Acclimating Your Fish}}</ref> Lowe & Vance (1995) were able to show that lizards acclimated to warm temperatures could maintain a higher running speed at warmer temperatures than lizards that were not acclimated to warm conditions.<ref name = "Lowe">{{cite journal | author = Lowe C.H., Vance V.J. | year = 1955 | title = Acclimation of the critical thermal maximum of the reptile ''Urosaurus ornatus'' | journal = Science | volume = 122 | issue = 3158| pages = 73–74 | doi=10.1126/science.122.3158.73| pmid = 17748800 | bibcode = 1955Sci...122...73L }}</ref> Fruit flies that develop at relatively cooler or warmer temperatures have increased cold or heat tolerance as adults, respectively (''See'' [[Drosophila melanogaster#Developmental plasticity|Developmental plasticity]]).<ref>{{Cite journal|last1=Slotsbo|first1=Stine|last2=Schou|first2=Mads F.|last3=Kristensen|first3=Torsten N.|last4=Loeschcke|first4=Volker|last5=Sørensen|first5=Jesper G.|date=2016-09-01|title=Reversibility of developmental heat and cold plasticity is asymmetric and has long-lasting consequences for adult thermal tolerance|url=https://jeb.biologists.org/content/219/17/2726|journal=Journal of Experimental Biology|language=en|volume=219|issue=17|pages=2726–2732|doi=10.1242/jeb.143750|issn=0022-0949|pmid=27353229|doi-access=free}}</ref>

====Humans====
{{See also|Cold and heat adaptations in humans}}

The [[salt]] content of sweat and urine decreases as people acclimatize to hot conditions.<ref name="armyheat">{{cite web|url=http://www.usariem.army.mil/pages/download/heatacclimatizationguide.pdf|archive-url=https://web.archive.org/web/20070702085236/http://www.usariem.army.mil/download/heatacclimatizationguide.pdf|archive-date=2007-07-02|title=Heat acclimatization guide|publisher=US Army|access-date=2009-07-02}}</ref> Plasma volume, heart rate, and capillary activation are also affected.<ref>{{Cite web|url=http://www.sportsci.org/encyc/heataccl/heataccl.html|title=Heat Acclimatization|website=www.sportsci.org|access-date=2017-12-03}}</ref>

[[Effects of high altitude on humans|Acclimatization to high altitude]] continues for months or even years after initial ascent, and ultimately enables humans to survive in an environment that, without acclimatization, would kill them. Humans who migrate permanently to a higher altitude naturally acclimatize to their new environment by developing an increase in the number of [[red blood cells]] to increase the [[oxygen]] carrying capacity of the [[blood]], in order to compensate for lower levels of [[oxygen]] intake.<ref name=Acclimatisation>{{cite journal |author1=Muza, SR |author2=Fulco, CS |author3=Cymerman, A |title=Altitude Acclimatization Guide. |journal=US Army Research Inst. Of Environmental Medicine Thermal and Mountain Medicine Division Technical Report |issue=USARIEM–TN–04–05 |year=2004 |url=http://archive.rubicon-foundation.org/7616 |access-date=2009-03-05 |archive-url=https://web.archive.org/web/20090423042451/http://archive.rubicon-foundation.org/7616 |archive-date=2009-04-23 |url-status=usurped }}</ref><ref name="Kenneth">{{cite web | author1=Kenneth Baillie | author2=Alistair Simpson | title=Altitude oxygen calculator | url=http://www.altitude.org/oxygen_levels.php | publisher=Apex (Altitude Physiology EXpeditions) | access-date=2006-08-10 | archive-url=https://web.archive.org/web/20170611073650/http://www.altitude.org/oxygen_levels.php | archive-date=2017-06-11 | url-status=dead }} - Altitude physiology model</ref>

==See also==
<!-- Please keep entries in alphabetical order & add a short description [[WP:SEEALSO]] -->
{{div col|colwidth=20em}}
* [[Acclimatisation society]]
* [[Beneficial acclimation hypothesis]]
* [[Heat index]]
* [[Introduced species]]
* [[Phenotypic plasticity]]
* [[Wind chill]]
{{div col end}}
<!-- please keep entries in alphabetical order -->

==References==
{{Reflist|30em}}

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[[Category:Physiology]]
[[Category:Ecological processes]]
[[Category:Climate]]
[[Category:Biology terminology]]