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Lecture 24: Ecosystem Ecology

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Western University
Biology 1001A
Beth Mac Dougall- Shackleton

Lecture 24: Ecosystem Ecology 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 Two Major Activities in Ecosystems: Production and Consumption • 4 major functional components: – Producers (autotrophs): green plants, fixing energy from the sun and creating organic material from carbon dioxide and energy – Consumers (heterotrophs): includes decomposers, requires other living organisms to feed off – Energy – Nutrients Where Does Energy Come From? • Light energy, harvested by photoautotrophs • Chemical energy, harvested by chemoautotrophs • Most energy that is fixed is done via photosynthesis Nutrients • Chemical elements or compounds needed for growth or reproduction – Organic (carbon-based) or inorganic – Micronutrients (nutrients needed in very small quantities such as selenium), macronutrients (nutrients needed in larger quantities such as oxygen or carbon) • Nutrient sources: – Geological sources (rocks or mineral soil) – Atmospheric sources – Oceans – Decomposition and nutrient cycling • Nutrients cycle through: – Living and dead organisms – Available nutrient reserves – Unavailable abiotic reserves 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 Ecological Efficiency < 100% • Harvesting efficiency: proportion of available food that is consumed • Assimilation efficiency: proportion of energy consumed that is assimilated (digested) • Production efficiency: proportion of ene
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