section_path: Mechanism/Competition
section_name: Competition
paragraph_text: Competition
  
  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 limited supply of a resource such as food, water, or territory. Competition may be within or between species, and may be direct or indirect. Species less suited to compete should 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 clades.
  
  Competition is modelled by r/K selection theory, which is based on Robert MacArthur and E. O. Wilson 's work on island biogeography. In this theory, selective pressures drive evolution in one of two stereotyped directions: r - or K -selection. These terms, r and K, can be illustrated in a logistic model of population dynamics:
  
  d N d t = r N (1 − N K) {\displaystyle {\frac {dN}{dt}}=rN\left(1-{\frac {N}{K}}\right)\qquad \!} where r is the growth rate of the population (N), and K is the carrying capacity of its local environmental setting. Typically, r -selected species exploit empty 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 invest more heavily in much fewer offspring, each with a relatively high probability of surviving to adulthood.