Chapter 43 Ecosystems & Human Interferences

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1 How do organisms obtain energy from their environment? Autotrophs produce their own food Heterotrophs feed on other organisms 1. Herbivores Consume plants 2. Carnivores Consume other animals 3. Omnivores Consume both plants & animals 4. Decomposers Feed on organic material in the soil Energy flow & Chemical Cycling All ecosystems are characterized by 2 fundamental phenomena Energy flow begins with the absorption of solar energy & ends with the production of heat Chemical cycling when inorganic materials are taken in by producers & then returned to the envirnoment

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5 Food webs & Trophic Levels Food web shows how organisms acquire their food Trophic level all the organisms that feed at a particular link in a food chain Ecological pyramids are illustrations of how the energy relationships exist between trophic levels 1. Pyramid of numbers illustrates how many organisms there are at each trophic level 2. Pyramids of biomass illustrates the total mass of organisms at each trophic level 3. Pyramid of energy illustrates the total energy at each trophic level Rule of 10% - only 10% of the energy of the previous trophic level is utilized by the next level 90% is lost as heat

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9 Global Biogeochemical Cycles Pathways by which chemicals circulate through ecosystems 1. Gaseous cycle The element returns to & is withdrawn from the atmosphere as a gas 2. Sedimentary cycle The element is absorbed from the sediment by plant roots & is returned to the soil by decomposers

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11 Carbon Dioxide (Carbon Cycle) & Global Warming Transfer rate The amount of a nutrient that moves from one component of the environment to another within a specified period of time Due to increased utilization of fossil fuel & wood burning the transfer rate is not equal Since 1850, the levels of carbon dioxide in the atmosphere has increased by 25% What are the consequences of this build up? The Greenhouse effect & Global warming Carbon dioxide & other gases impede the escape of infrared radiation from the surface of the earth Result Increased temperature = more drought conditions = decreased agricultural output

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14 Nitrogen Cycle & Air Pollution Nitrogen makes up 78% of the Earth s atmosphere but plants cannot incorporate nitrogen gas directly & must rely upon bacteria to help them out Nitrogen fixation Occurs when nitrogen is converted to other forms including ammonia & nitrate which the plants can take up to form other biomolecules Nitrification Is the production of nitrates via either the bacteria or under atmospheric energy conditions (lightning, meteor trails, etc) Denitrification Conversion of nitrate to nitrous oxide & nitrogen gas What are the consequences of altering the transfer rate of nitrogen? Fossil fuel input The atmosphere contains 3X the nitrogen oxide levels than it should have Nitrogen oxide when combined with water vapor in the atmosphere form acids = acid rain Nitrogen oxides can also combine with hydrocarbons & in the presence of sunlight = smog

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19 Human Impact of Biodiversity Ozone depletion Increased UV radiation reaching the earth = Camcer Tropical Rain Forest Destruction 1. Loss of carbon dioxide sink 2. Loss of potentially beneficial organisms (Loss of biodiversity) All leads to a heightened awareness of the need for Conservation Biology The scientific study of biodiversity, leading to the preservation of species & the management of ecosystems for sustainable human welfare