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Biology Lecture 24.docx

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Biology 1001A
Tom Haffie

Biology Lecture 24: Ecosystem Ecology  A few terms: o Community: all of the organisms living in some defined place o Ecosystem: a biotic community and its abiotic environment functioning as a system o Ecosystems are open systems (not closed)  2 major activities in ecosystems: production, consumption: o Production: new biomass is being created from inorganic substances o Consumption: previously created biomass is being converted to new forms of biomass o 4 major components:  Producers (autotrophs): make their own food (usually from the sun)  Consumers (heterotrophs): everything that has to eat something else (this includes decomposers)  Energy  Nutrients  Where does the energy come from? o In most ecosystems energy comes from the sun (light energy)  Photoautotroph's utilize this light energy to create biomass (creating energy by photosynthesis) o Chemoautotrophs depend on chemical energy to produce biomass (occurs when the sun is not present to produce energy)  Nutrients: o Any chemical element that is needed for living things to grow or reproduce  Organic or inorganic:  Organic simply means carbon containing (exception of2CO , carbonate)  Micronutrients: something that organisms need in small quantities (Ex: iron)  Macronutrients: something that an organism needs a lot of (Ex: oxygen) o Nutrient sources: geological sources (mineral soil), atmospheric sources, oceans, decomposition & nutrient cycling  Energy flows up the food web...: o Energy flows from sources through primary produces through consumers and decomposers  Ecological inefficiency: some energy is lost at each transfer between levels  Energy constantly being replaced from outside the ecosystem  Ecological efficiency <100%: o Harvesting efficiency: the portion of available food that is consumed (always <100%) o Assimilation of efficiency: the proportion of energy consumed that is assimilated or digested (always <100%) o Production efficiency: the portion of energy assimilated or digested that becomes new tissue (always <100%)  Clicker Question: On average, how much energy contained in a given trophic level is available for the next higher trophic level? A. About 90% B. About 50% C. About 10%  Clicker Question: Which of the following humans is at the highest trophic level? A. Alice, who eats plants. B. Betty, who eats mostly alligator steaks. C. Cameron, Betty's baby, who e
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