Food webs - Food webs 6/4/11 What is a food web?...

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6/4/11 Food webs
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6/4/11 What is a food web? Description of who eats whom within a community Holistic representation of trophic interactions. In effect, we are ‘zooming out’… taking a broader perspective
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6/4/11 Charles Elton introduced the food web concept Elton 1927 : ‘There are in fact chains of animals linked together by food and all in the long run dependent on plants. We refer to these as ‘food chains’ and to all the food chains in the community as a food cycle’
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6/4/11 Food chains and food webs All ecological communities are composed of multiple trophic levels. Linear food chains are usually insufficient to describe feeding links within a community because 1) trophic levels typically have >1 species; 2) Many consumers feed on more than one
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6/4/11 Food web terminology (II) Linkage density = average number of links per species ( L / S ) 6 Connectance = total number of links/number of possible links ( L/S2 ). This includes cannibalism and mutual predation. 6 Chain length = number of links from the top predator to the basal species. Max chain length is a measure of number of trophic levels present
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6/4/11 Food web terminology (I) Food webs are composed of nodes , each representing a single species or a group of species thought to be trophicacally similar (trophospecies). Number of species/nodes = S 6 Interactions between species are represented by links ( L ) l Basal species = species occupying the lowest trophic level
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6/4/11 How are food webs Connectedness (topological) food web Energy web Functional food web
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6/4/11 Food web special features Cycles: reciprocal predatory relationship between 2 species Cannibalism: feeding upon members of the same species Omnivory: feeding on more than one trophic level
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6/4/11 How many trophic levels? Relatively low
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This note was uploaded on 06/04/2011 for the course PCB 4043 taught by Professor Osenberg during the Fall '10 term at University of Florida.

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Food webs - Food webs 6/4/11 What is a food web?...

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