Editing Natural selection (section)

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

In biology, competition is an interaction between organisms in which the fitness of one is lowered by the presence of another. This may be because both rely on a [[Limiting factor|limited]] supply of a resource such as food, water, or [[Territory (animal)|territory]].<ref>{{harvnb|Begon|Townsend|Harper|1996}}</ref> Competition may be [[intraspecific competition|within]] or [[interspecific competition|between species]], and may be direct or indirect.<ref name="SahneyBentonFerry2010LinksDiversityVertebrates">{{cite journal |last1=Sahney |first1=Sarda |last2=Benton |first2=Michael J. |author-link2=Michael Benton |last3=Ferry |first3=Paul A. |date=23 August 2010 |title=Links between global taxonomic diversity, ecological diversity and the expansion of vertebrates on land |journal=[[Biology Letters]]|volume=6 |issue=4 |pages=544–547 |doi=10.1098/rsbl.2009.1024 |pmc=2936204 |pmid=20106856}}</ref> Species less suited to compete should [[competitive exclusion principle|in theory either adapt or die out]], since competition plays a powerful role in natural selection, but according to the "room to roam" theory it may be less important than expansion among larger [[clade]]s.<ref name="SahneyBentonFerry2010LinksDiversityVertebrates"/><ref name="Jardine2012">{{cite journal |last1=Jardine |first1=Phillip E. |last2=Janis |first2=Christine M. |last3=Sahney |first3=Sarda |last4=Benton |first4=Michael J. |date=1 December 2012 |title=Grit not grass: Concordant patterns of early origin of hypsodonty in Great Plains ungulates and Glires |journal=[[Palaeogeography, Palaeoclimatology, Palaeoecology]] |volume=365–366 |pages=1–10 |doi=10.1016/j.palaeo.2012.09.001|bibcode=2012PPP...365....1J }}</ref>

Competition is modelled by [[r/K selection theory|''r/K'' selection theory]], which is based on [[Robert MacArthur]] and [[E. O. Wilson]]'s work on [[Insular biogeography|island biogeography]].<ref>{{harvnb|MacArthur|Wilson|2001}}</ref> In this theory, selective pressures drive evolution in one of two stereotyped directions: ''r''- or ''K''-selection.<ref>{{cite journal |last=Pianka |first=Eric R. |author-link=Eric Pianka |date=November–December 1970 |title=On ''r''- and ''K''-Selection |journal=[[The American Naturalist]] |volume=104 |number=940 |pages=592–597 |doi=10.1086/282697 |jstor=2459020|bibcode=1970ANat..104..592P |s2cid=83933177 }}</ref> These terms, ''r'' and ''K'', can be illustrated in a [[Logistic function#In ecology: modeling population growth|logistic model]] of [[population dynamics]]:<ref name=Verhulst>{{cite journal |last=Verhulst |first=Pierre François |author-link=Pierre François Verhulst |year=1838 |title=''Notice sur la loi que la population suit dans son accroissement'' |url=https://archive.org/details/correspondancem02belggoog |language=fr |journal=Correspondance Mathématique et Physique |location=Brussels, Belgium |volume=10 |pages=113–121 |oclc=490225808}}</ref>

<math display="block">\frac{dN}{dt}=rN\left(1 - \frac{N}{K}\right) \qquad \!</math>
where ''r'' is the [[Population growth#Population growth rate|growth rate]] of the population (''N''), and ''K'' is the [[carrying capacity]] of its local environmental setting. Typically, ''r''-selected species exploit empty [[Ecological niche|niches]], and produce many offspring, each with a relatively low [[probability]] of surviving to adulthood. In contrast, ''K''-selected species are strong competitors in crowded niches, and [[Parental investment|invest]] more heavily in much fewer offspring, each with a relatively high probability of surviving to adulthood.<ref name=Verhulst/>