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Lecture35_Ecosystems - On land production is limited by •...

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Ecosystem Ecology I. Introduction to ecosystems An ecosystem consists of the species present in an area and the abiotic environment The major components of an ecosystem: • external energy source: • primary producers: convert an external source of energy into • consumers (including decomposers) heterotrophs—they • abiotic (physical) environment How do these components interact? Via movement of external energy/nutrient source primary producers abiotic environment consumers decomposers II. Energy relationships in ecosystems A. Definitions • Primary productivity = amount of energy captured by photosynthesis • Net primary productivity (NPP) = primary production used to build tissue B. Patterns in primary productivity 1. Comparing plant communities • where is NPP high? low? • why is NPP of open ocean so low? • why is % of NPP of open ocean so high? Note habitats in particular trouble re loss:
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2. Comparing regions of the world • What limits productivity in terrestrial habitats?
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Unformatted text preview: On land, production is limited by • Where is productivity highest in marine habitats? C. Analyzing energy flow: What happens to primary production? e.g. Hubbard Brook experimental forest, NH external energy/nutrient source kcal/m 2 /year primary producers of the energy in sunlight is captured by photosynthesis of this: % to growth*; % to respiration consumers decomposers % to herbivores % in dead material * D. Trophic levels among consumers and decomposers Trophic level Feeding strategy Grazing food chain Decomposer food chain 5 4 consumer 4 3 consumer 3 2 consumer 2 1 consumer 1 Autotroph add other species that eat algae and cyanobacteria E. How does energy flow from producers to consumers? Why is so much energy lost at each trophic level? • • • III. Biogeochemical cycles … bio … geo … chemical … the other way that components of ecosystem are connected e.g. nitrogen cycle, carbon cycle … Humans are...
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