Editing Food web (section)

===Food chain===
{{Main|food chain}}

A common metric used to quantify food web trophic structure is food chain length. Food chain length is another way of describing food webs as a measure of the number of species encountered as energy or nutrients move from the plants to top predators.<ref name="Post93">{{cite journal|last=Post|first=D. M.|title= The long and short of food-chain length|year=1993|journal = Trends in Ecology and Evolution|volume=17|issue=6| pages=269–277|doi=10.1016/S0169-5347(02)02455-2}}</ref>{{Rp|269}} There are different ways of calculating food chain length depending on what parameters of the food web dynamic are being considered: connectance, energy, or interaction.<ref name="Post93" /> In its simplest form, the length of a chain is the number of links between a trophic consumer and the base of the web. The mean chain length of an entire web is the arithmetic average of the lengths of all chains in a food web.<ref name="Odum">{{cite book | last1=Odum | first1=E. P. | last2=Barrett | first2=G. W. | title=Fundamentals of ecology | publisher=Brooks Cole <!--| isbn= 0-534-42066-4--> | isbn=978-0-534-42066-6 | year=2005 | page=598 | url=http://www.cengage.com/search/totalsearchresults.do?N=16&image.x=0&image.y=0&keyword_all=fundamentals+of+ecology }}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="Pimm79">{{cite journal |last1=Pimm |first1=S. L. |title=The structure of food webs |journal=Theoretical Population Biology |volume=16 |issue=2 |pages=144–158 |year=1979 |url=http://www.nicholas.duke.edu/people/faculty/pimm/publications/pimmreprints/12_Pimm_TPB_1979.pdf |doi=10.1016/0040-5809(79)90010-8 |pmid=538731 |bibcode=1979TPBio..16..144P |url-status=dead |archive-url=https://web.archive.org/web/20110927230926/http://www.nicholas.duke.edu/people/faculty/pimm/publications/pimmreprints/12_Pimm_TPB_1979.pdf |archive-date=2011-09-27 |accessdate=2011-06-13 }}</ref>

In a simple predator-prey example, a deer is one step removed from the plants it eats (chain length = 1) and a wolf that eats the deer is two steps removed from the plants (chain length = 2). The relative amount or strength of influence that these parameters have on the food web address questions about:
* the identity or existence of a few dominant species (called strong interactors or keystone species)
* the total number of species and food-chain length (including many weak interactors) and
* how community structure, function and stability is determined.<ref name="Worm03">{{cite journal|last1=Worm|first1=B.|last2=Duffy|first2=J.E.|title= Biodiversity, productivity and stability in real food webs|year=2003|journal = Trends in Ecology and Evolution|volume=18|issue=12| pages=628–632|doi=10.1016/j.tree.2003.09.003|bibcode=2003TEcoE..18..628W }}</ref><ref name="Paine80">{{cite journal | last1=Paine | first1=R. T. | s2cid=55981512 | title=Food webs: Linkage, interaction strength and community infrastructure. | journal=Journal of Animal Ecology | volume=49 | issue=3 | year=1980 | pages=666–685 | jstor=4220 | doi=10.2307/4220| bibcode=1980JAnEc..49..666P }}</ref>