Ecology (source code)
= Ecology
The goal of <ecology> is to explain where <organisms> live, how many there are, and how their interactions with one another and their surroundings change those patterns. Living partners include <prey>, <predators> and <parasites>; nonliving conditions include <light>, <temperature> and <water>. An <ecosystem> brings these interacting parts into one study system. See https://openstax.org/books/biology-2e/pages/44-1-the-scope-of-ecology[Clark, Douglas and Choi, Biology 2e, 44.1: the scope of ecology].
Start with an invented aquatic <food web>: photosynthetic <algae> feed <zooplankton>, which feed small <fish>, which feed large <fish>. That <food chain> has four feeding positions and three feeding arrows. Dead material also reaches <decomposers> through <detritus>, so the <food web> branches rather than forming a single ladder.
\Image[/illustrative-food-web.png]
{title=An illustrative aquatic <food web>: feeding arrows point from resource to <consumer>}
{description=Original schematic, not a measured <ecosystem>. Solid arrows mean RESOURCE → CONSUMER; dashed arrows mean transfer of dead material to <detritus>. Box sizes and arrow widths do not represent abundance or transfer rates. <Algae>, <zooplankton>, small <fish> and large <fish> are generic groups, not identified <species>. Selected dead-material transfers are shown; further feeding and recycling routes are omitted.}
The appeal of <ecology> is that an <organism>'s surroundings include other <organisms> that change those surroundings. <Photosynthesis> links <light> to living material; <predation> transfers that material between <organisms>; <decomposers> return its constituent <chemical elements> to forms that can be used again. These connections help explain why changing one part of an <ecosystem> can affect distant parts of its <food web>, although an arrow alone does not predict the size or even the direction of an indirect change. <Population dynamics> supplies quantitative tools when the question concerns changing counts.
In 1866, Ernst Haeckel's \i[Generelle Morphologie der Organismen] included a section titled \i[Oecologie und Chorologie] in volume 2, beginning on page 286. This places the terminology of <ecology> in an early systematic treatment of <organisms> and their relationships. See https://books.google.com/books?id=tKFbIVgJS8wC[Haeckel, Generelle Morphologie der Organismen, volume 2 (1866), contents and p. 286]. A later quantitative landmark is Raymond L. Lindeman's 1942 treatment of <ecosystems> through feeding relationships and <energy flow>. See https://doi.org/10.2307/1930126[Lindeman, The Trophic-Dynamic Aspect of Ecology, Ecology 23 (1942), 399–417].
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