Introduction to evolution: Difference between revisions

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Coevolution is a process in which two or more species influence the evolution of each other. All organisms are influenced by life around them; however, in coevolution there is evidence that genetically determined traits in each species directly resulted from the interaction between the two organisms.<ref name="NAS" />

An extensively documented case of coevolution is the relationship between ''[[Pseudomyrmex]]'', a type of [[ant]], and the ''[[acacia]]'', a plant that the ant uses for food and shelter. The relationship between the two is so intimate that it has led to the evolution of special structures and behaviours in both organisms. The ant defends the acacia against [[herbivore]]s and clears the forest floor of the [[seed]]s from competing plants. In response, the plant has evolved swollen thorns that the ants use as shelter and special flower parts that the ants eat.<ref>{{cite journal |last=Janzen |first=Daniel H. |author-link=Daniel H. Janzen |year=1974 |title=Swollen-Thorn Acacias of Central America |url=http://www.sil.si.edu/smithsoniancontributions/Botany/pdf_hi/sctb-0013.pdf |journal=[[Smithsonian Contributions and Studies Series|Smithsonian Contributions to Botany]] |___location=Washington, D.C. |publisher=[[Smithsonian Institution|Smithsonian Institution Press]] |volume=13 |issue=13 |pages=1–131 |doi=10.5479/si.0081024X.13 |oclc=248582653 |access-date=2007-08-31}}</ref>

Such coevolution does not imply that the ants and the tree choose to behave in an [[altruism|altruistic]] manner. Rather, across a population small genetic changes in both ant and tree benefited each. The benefit gave a slightly higher chance of the characteristic being passed on to the next generation. Over time, successive mutations created the relationship we observe today.