Editing Model organism (section)

{{short description|Organisms used to study biology across species}}
[[File:E coli at 10000x, original.jpg|thumb | right | ''[[Escherichia coli]]'' is a [[gram-negative bacteria|gram-negative]] [[prokaryote|prokaryotic]] model organism]]
[[File:Drosophila melanogaster - side (aka).jpg|thumb | ''[[Drosophila melanogaster]]'', one of the most famous subjects for [[genetics]] experiments]]
[[File:S cerevisiae under DIC microscopy.jpg|thumb | ''[[Saccharomyces cerevisiae]]'', one of the most intensively studied [[Eukaryote|eukaryotic]] model organisms in [[molecular biology|molecular]] and [[cell biology]]]]

{{also|List of model organisms}}
A '''model organism''' is a [[non-human]] [[species]] that is extensively studied to understand particular [[biology|biological]] phenomena, with the expectation that discoveries made in the [[model]] organism will provide insight into the workings of other organisms.<ref>{{cite journal |last1=Fields |first1=S. |last2=Johnston |first2=M |title=CELL BIOLOGY: Whither Model Organism Research? |journal=Science |date=2005-03-25 |volume=307 |issue=5717 |pages=1885–1886 |doi=10.1126/science.1108872 |pmid=15790833 }}</ref><ref>Griffiths, E. C. (2010) [http://www.emily-griffiths.postgrad.shef.ac.uk/models.pdf What is a model?] {{webarchive |url=https://web.archive.org/web/20120312220527/http://www.emily-griffiths.postgrad.shef.ac.uk/models.pdf |date=March 12, 2012 }}</ref> Model organisms are widely used to research human [[disease]] when [[human experimentation]] would be unfeasible or [[bioethics|unethical]].<ref>{{cite book|url=https://books.google.com/books?id=yTfNH3cScKAC<!--confirmed ISBN match; full text access-->|title=The Case for Animal Experimention: An Evolutionary and Ethical Perspective|last=Fox|first=Michael Allen|publisher=University of California Press|year=1986|isbn=978-0-520-05501-8|location=Berkeley and Los Angeles, California|oclc=11754940|via=Google Books}}</ref> This strategy is made possible by the [[common descent]] of all living organisms, and the conservation of [[Metabolic pathway|metabolic]] and [[developmental biology|developmental]] pathways and [[genetic material]] over the course of [[evolution]].<ref>{{cite journal |last1=Allmon |first1=Warren D. |last2=Ross |first2=Robert M. |title=Evolutionary remnants as widely accessible evidence for evolution: the structure of the argument for application to evolution education |journal=Evolution: Education and Outreach |date=December 2018 |volume=11 |issue=1 |pages=1 |doi=10.1186/s12052-017-0075-1 |doi-access=free }}</ref>

Research using animal models has been central to most of the achievements of modern medicine.<ref name=RSM2015/><ref name=NRCIOM/><ref name="Nature2007"/> It has contributed most of the basic knowledge in fields such as human [[physiology]] and [[biochemistry]], and has played significant roles in fields such as [[neuroscience]] and [[infectious disease]].<ref name=NRCIOMb/><ref name="HLAS2011"/> The results have included the near-[[Poliomyelitis eradication|eradication of polio]] and the development of [[organ transplantation]], and have benefited both humans and animals.<ref name=RSM2015/><ref name="IOM1991"/> From 1910 to 1927, [[Thomas Hunt Morgan]]'s work with the fruit fly ''[[Drosophila melanogaster]]'' identified [[chromosome]]s as the vector of inheritance for genes,<ref name="nobelprize.org"/><ref name="nobel2"/> and [[Eric Kandel]] wrote that Morgan's discoveries "helped transform biology into an experimental science".<ref name="Kandel1999"/> Research in model organisms led to further medical advances, such as the production of the [[diphtheria antitoxin]]<ref name="nobel3"/><ref name="Cannon2009"/> and the 1922 discovery of [[insulin]]<ref name="insulin"/> and its use in treating diabetes, which had previously meant death.<ref name="Thompson2009"/> Modern general anaesthetics such as [[halothane]] were also developed through studies on model organisms, and are necessary for modern, complex surgical operations.<ref name="raventos1956"/> Other 20th-century medical advances and treatments that relied on research performed in animals include [[organ transplant]] techniques,<ref name="carrel1912"/><ref name="williamson1926">Williamson C (1926) ''J. Urol.'' 16: p. 231</ref><ref name="woodruff1986"/><ref name="moore1964"/> the heart-lung machine,<ref name="gibbon1937"/> [[antibiotic]]s,<ref name="rawbw"/><ref name="Streptomycin"/><ref name="fleming1929"/> and the [[whooping cough]] vaccine.<ref name="mrc1956"/>

In researching human [[disease]], model organisms allow for better understanding the disease process without the added risk of harming an actual human. The species of the model organism is usually chosen so that it reacts to disease or its treatment in a way that resembles human [[physiology]], even though care must be taken when generalizing from one organism to another.<ref>{{Cite book|title=Essential Developmental Biology|last=Slack|first=Jonathan M. W.|publisher=Wiley-Blackwell|year=2013|location=Oxford|oclc=785558800}}</ref> However, many drugs, treatments and cures for human diseases are developed in part with the guidance of animal models.<ref name="zam">{{cite journal |last1=Chakraborty |first1=Chiranjib |last2=Hsu |first2=Chi |last3=Wen |first3=Zhi |last4=Lin |first4=Chang |last5=Agoramoorthy |first5=Govindasamy |title=Zebrafish: A Complete Animal Model for In Vivo Drug Discovery and Development |journal=Current Drug Metabolism |date=2009-02-01 |volume=10 |issue=2 |pages=116–124 |doi=10.2174/138920009787522197 |pmid=19275547 }}</ref><ref name=zrug>{{cite journal |last1=Kari |first1=G |last2=Rodeck |first2=U |last3=Dicker |first3=A P |title=Zebrafish: An Emerging Model System for Human Disease and Drug Discovery |journal=Clinical Pharmacology & Therapeutics |date=July 2007 |volume=82 |issue=1 |pages=70–80 |doi=10.1038/sj.clpt.6100223 |pmid=17495877 }}</ref> Treatments for animal diseases have also been developed, including for [[rabies]],<ref name="buck1904"/> [[anthrax]],<ref name="buck1904" /> [[glanders]],<ref name="buck1904" /> [[feline immunodeficiency virus]] (FIV),<ref name="pu2005"/> [[tuberculosis]],<ref name="buck1904" /> Texas cattle fever,<ref name="buck1904" /> [[classical swine fever]] (hog cholera),<ref name="buck1904" /> [[heartworm]], and other [[Parasitic disease|parasitic infections]].<ref name="dryden2005"/> Animal experimentation continues to be required for biomedical research,<ref name=bundle/> and is used with the aim of solving medical problems such as Alzheimer's disease,<ref name="geula1998"/> AIDS,<ref name="AIDS2005"/> multiple sclerosis,<ref name="jameson1994"/> spinal cord injury, many headaches,<ref name="lyuksyutova1984"/> and other conditions in which there is no useful ''[[in vitro]]'' model system available.

Model organisms are drawn from all three [[Domain (biology)|domains]] of life, as well as [[virus]]es. One of the first model systems for [[molecular biology]] was the bacterium ''[[Escherichia coli]]'' (''E. coli''), a common constituent of the human digestive system. The mouse (''[[House mouse|Mus musculus]]'') has been used extensively as a model organism and is associated with many important biological discoveries of the 20th and 21st centuries.<ref name="Hedrich"/> Other examples include baker's yeast (''[[Saccharomyces cerevisiae]]''), the [[T4 phage]] virus, the [[Drosophilidae|fruit fly]] ''[[Drosophila melanogaster]]'', the flowering plant ''[[Arabidopsis thaliana]]'', and [[guinea pig]]s (''Cavia porcellus''). Several of the bacterial viruses ([[bacteriophage]]) that infect ''[[Escherichia coli|E. coli]]'' also have been very useful for the study of gene structure and [[gene regulation]] (e.g. phages [[Lambda phage|Lambda]] and [[Enterobacteria phage T4|T4]]).<ref>{{cite journal |last1=Grada |first1=Ayman |last2=Mervis |first2=Joshua |last3=Falanga |first3=Vincent |date=October 2018 |title=Research Techniques Made Simple: Animal Models of Wound Healing |journal=Journal of Investigative Dermatology |volume=138 |issue=10 |pages=2095–2105.e1 |doi=10.1016/j.jid.2018.08.005 |pmid=30244718 |doi-access=free}}</ref> Disease models are divided into three categories: homologous animals have the same causes, symptoms and treatment options as would humans who have the same disease, isomorphic animals share the same symptoms and treatments, and predictive models are similar to a particular human disease in only a couple of aspects, but are useful in isolating and making predictions about mechanisms of a set of disease features.<ref>{{cite web | url=http://academic.uprm.edu/~ephoebus/id85.htm | title=Pinel Chapter 6 - Human Brain Damage & Animal Models | publisher=Academic.uprm.edu | access-date=2014-01-10 | archive-url=https://web.archive.org/web/20141013041340/http://academic.uprm.edu/~ephoebus/id85.htm | archive-date=2014-10-13 | url-status=dead }}</ref>