01 2ary cons 1 primary productivity bottom up

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Unformatted text preview: s Trophic pyramid: decreasing energy transfer to higher trophic levels 3ary Cons. (0.1%) 2ary Cons. (1%) Primary productivity Bottom-up controls Abiotic factors (physical, chemical) 1ary Consumers (10%) 1ary Producers (100%) Why are efficiency levels so low? Maintenance, growth, reproduction Some components of food not easily assimilated (e.g. arthropod exoskeletons, bone, cellulose) Animals excrete a portion of assimilated energy in the form of nitrogenous wastes Influences on primary productivity: Consumers Top-down controls Primary productivity Bottom-up controls Abiotic factors (physical, chemical) Trophic cascades: consumer-resource interaction affects species (trophic levels) beyond those that are directly involved (beyond “link” in the food web) Terrestrial trophic cascade -+ +-+ % leaf area lost to herbivory predatory ant +- top-down effect of beetle leaf area/tree (cm2) predatory beetle % of tree occupied by ants experiment: beetle vs no beetle months after experiment began Dyer & Letourneau 1999 Food webs: models that help define energy flows & predator-prey relationships in ecosystem complex & dynamic, some spp involved in multiple levels Food webs: influence community composition, stability, diversity removal of sea stars from intertidal sites: mussels spread, diversity reduced by 50% Keystone species: large effect, out of proportion to their abundance (perform “key function”) often consumers (predators, herbivores) but also mutualists pollination Dominant species: large effect bc high abundance/biomass seed dispersal Ecosystem engineers: large effect bc alter environment (incl. agriculture) flying foxes: pollination/seed dispersal for 75% of canopy trees Trophic Levels & Interactions -things to remember - - Primary productivity, what factors limit it Autotrophs & heterotrophs Types of symbioses, examples Trophic efficiency, why it is low Trophic cascades Food webs & keystone species next Wednesday Movie (print worksheet) next Monday review of material for exam in form of Ecology Jeopardy 1st EXAM Wednesday, Feb 19...
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This document was uploaded on 03/17/2014 for the course BIO SCI 310 at Wisconsin Milwaukee.

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