Lec29_30+Study+Guides - BIS2B Lectures 29&30 Fall 2008...

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BIS2B Fall 2008 D. R. Strong Lectures 29&30 Food webs & Decomposition More on direct and indirect interactions in food webs : Direct interspecific interactions are a big part of nature. Recall our examples of direct interspecific competition, in which pairs of species sense, respond, and negatively affect each other (head to head, mano a mano , etc). 1. Cthamalus and Balanus barnacle species, mechanism = overgrowth. 2. Wolves and ravens, mechanism = removal of meat from moose carcass and its prevention by physical intimidation. One or a few wolves threatens single or a few ravens with snarl; the wolf could easily kill or maim a raven. If many ravens and few wolves, the table are turned. One or a few ravens can lead the threatening wolf off of the kill while others remove meat. There is the possibility of many ravens pecking eyes of single or few wolves, which if starving would tend to be reckless on the kill. These are prime examples of the kind of objective observations from science that led to the famous quote, Tho' Nature, red in tooth and claw With ravine, shriek'd against his creed. . From A. Tennyson’s In Memoriam A.H.H. in 1849 (what happened in that year?). As the Wikipedia puts it, this poem “…can be seen as reflective of Victorian society at the time, and the poem discusses many of the issues that were beginning to be questioned.” Apologies to Bob Dylan, The times they (were) a changin’. Examples of direct interspecific predation, herbivory:
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This note was uploaded on 08/23/2009 for the course BIS BIS 2B taught by Professor Staff during the Fall '09 term at UC Davis.

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Lec29_30+Study+Guides - BIS2B Lectures 29&30 Fall 2008...

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