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Lec 24.docx

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Biology 1001A
Tom Haffie

Lec 24: Ecosystem Ecology • Energy flows, nutrients cycle • Pyramids of energy, biomass, numbers • Nutrient cycles and reserves: water, carbon • We have been gradually increasing in the scale of organization • We will be looking at how energy and nutrients move throughout an ecosystem • More energy available at lower trophic levels • Know the water and carbon cycle A few terms… • Community: all of the organisms living in some defined place • Ecosystem: a biotic community and its abiotic environment functioning as a system • Ecosystems are open, not closed systems – energy inputs and outputs – nutrient inputs and outputs - Ecosystem involves the community and it also includes the abiotic components of the environment - Ecosystems are fundamentally open systems (energy, nutrients) that means that any ecosystem on earth is going to require some source of energy input (light energy from the sun). Many ecosystems give energy to the environment or to other ecostsyems in the form of sound or heat. - Ecosystems are not sealed off in terms of nutrients aswell. - Streams feeding into a lake (example of nutrient intake) 2 major activities in ecosystems: production, consumption 4 major functional components: Producers (autotrophs) Consumers (heterotrophs): includes decomposers Energy Nutrients - Production- new biomass is being created from inorganic substances - Consumption- biomass that is alreay created is being converted to other forms of biomass - Autotroughs at the bottom make their own food - Primary consumers- (heterotrough) - An ecosystem has the abiotic environment (energy and sun) Where does the energy come from? • light energy, harvested by photoautotroughs • chemical energy, harvestes by chemoautotrophs • Without energy, we cant drive the processes to sustain life • Organisms that produce energy via photosynthesis are called photoautotroughs • Chemoautotrophs rely on chemical energy to create energy (in areas where the sun doesn’t shine)- organisms that harvest energy by reducing sulfur ex. Microbial communities Nutrients • Chemical elements or compounds needed for growth or reproduction in living things – organic or inorganic – micronutrients, macronutrients • Nutrient sources: – geological sources (mineral soil) – atmospheric sources – oceans – decomposition & nutrient cycling • Organic- means they are comprised of carbon • Inorganic- CO2 is considered inorganic rather then organic • Micro and macro nutrients- in excessive quantities can be toxic • Micronutrient is something that organisms need in trace quantities (small amounts) • Macronutrients are something that organisms need in large quantities • Nutrients are stored in a variety places • -geological sources- temporarily bound up in rocks • Atmospheric source- where a large portion of oxygen and nitrogen would be • Oceans- minerals dissolved in the oceans • Decomposition and nutrient cycling- if it werent for this, we would eventually run out of available nutrients) Energy flows up the food web… • energy flows from source through primary producers through consumers and decomposers – ecological inefficiency: some energy lost at each transfer between levels – energy constantly being replaced from outside the ecosystem • - Energy typically flows up the grazing food web or into the decomposing food web • - Not all the energy harvested will make it to the top (ecological inefficiency)- some energy is going to be lost, that’s why ecosystems need a constant flow of new energy Ecological efficiency < 100% Ecological efficiency is the product of three things: - harvesting efficiency- proportion of available food that is consumed - assimilation efficiency- proportion of energy consumed that is assimilated (digested) - production efficiency- proportion of energy assimilated that becomes new tissue - this is because harvesting energy is less the 100% (they cant captu
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