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Ecosystems & The Flow of Energy & Matter PACKET #80 CHAPTERS #54 & #50 Introduction Ecosystem Encompasses all the interactions among organisms living together in a particular place, and among those organisms and their abiotic environments Individual communities and their abiotic environments Earth, which encompasses the biosphere (all of Earth’s communities) and its interaction with Earth’s water, soil, rock and atmosphere, is the largest ecosystem Ecosystems ENERGY FLOW Energy Flow Through Ecosystems The flow of energy is linear—as energy cannot be reused by organisms Energy begins as solar energy, which is trapped by photosynthesis in the form of chemical energy Chemical energy is then available to do work Energy Flow II Energy flow describes who eats whom in ecosystems A food chain describes the sequential passage of energy A food web shows the complexity of interconnected food chains Remember that a food web is composed of many food chains Energy Flow III Food Chain Refresher Primary producers are autotrophs and comprise the first trophic level Herbivores, primary consumers, comprise the second trophic level May find omnivores here Carnivores and/or omnivores, comprise trophics level three and higher all the way to the decomposers Energy Flow IV Ecological Pyramid Illustrates the trophic levels May be a pyramid of Numbers Energy Flow V Ecological Pyramid Illustrates the trophic levels May be a pyramid of Biomass Energy Flow VI Ecological Pyramid Illustrates the trophic levels May be a pyramid of Energy Ecosystems PRODUCTIVITY Productivity I Energy flow begins with primary productivity The amount of light energy converted to chemical energy, in the form of organic molecules, by an ecosystem’s autotrophs, over a given period of time. Gross Primary Productivity (kilocalories fixed per area per time OR grams carbon fixed) Expresses the total rate of photosynthesis of an ecosystem Net Primary Productivity (kilocalories fixed per area per time OR grams carbon fixed) The energy remaining after cellular respiration Gross total productivity – energy used for cellular respiration Productivity II Primary Productivity is always expressed as a RATE and is represented via Kilocalories fixed per area per time Joules per square meter per year Grams carbon fixed (Biomass) The dry weight of vegetation added to an ecosystem per unit area per unit time Grams per square meter per year Productivity III Rates of productivity are influenced by environmental factors Tropical rain forests are the most productive terrestrial ecosystems Wetlands, coral reefs, and estuaries are the most productive aquatic ecosystems Productivity IV Energy flow is never 100% efficient and results in the Pyramid of Productivity Productivity V Relationship of productivity to biological diversity is complex Ecosystems may be more diverse as productivity increases, but after a certain point, diversity will decline with increasing productivity Important when considering nutrient-enriched environments Especially those that are impacted by human application of fertilizers and enrichment by animal wastes. Cycles of Matter in Ecosystem Introduction Biochemical cycles are cycles of matter between the abiotic and biotic components of the environment Carbon, nitrogen, phosphorus and water cycles are central to life on earth Carbon, nitrogen and water cycles have atmospheric components and cycle on a global scale Carbon Cycle Carbon dioxide is the pivotal molecule in the carbon cycle Human activities, since the beginning of the Industrial Revolution, have contributed an increasing amount of carbon dioxide to the atmosphere by burning fossil fuels Nitrogen Cycle Bacteria are essential to this cycle Nitrogen fixing bacteria converts nitrogen gas to ammonia Nitrifying bacteria converts ammonia to nitrate Denitrifying bacteria converts, anaerobes, convert nitrate to nitrogen gas Nitrogen is needed for the production of proteins Nitrogen oxides are also an ingredient in photochemical smog Phosphorus Cycle Fertilizers, runoff containing animal wastes, and sewage introduce phosphorus into aquatic ecosystems Phosphorus loss accelerated by clear cutting Brazil Water Cycle Enough said! Abiotic Factors in Ecosystems THE SUN The Sun Warms the earth Solar energy biogeochemical cycles Temperature changes with latitude Sun’s rays strike the equatorial regions vertically which result in warmer temperatures The Sun II Temperature changes with season Tilting of the Earth’s axis causes the amount of solar radiation to vary during the year How does this help with the establishment of ocean currents? How does temperature change help with support life in standing bodies of water? More to come Review