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ECOSYSTEMS AND ENERGY FLOW CH 36 I. Feeding Relationships and Energy Flow A. Types of Organisms All organisms require an input of energy to carry out their life processes like growing, moving, and reproducing Producers: obtain energy from the sun by converting it to glucose (autotrophs) Consumers: obtain energy by eating producers or other consumers (heterotrophs) Decomposers (detrivores): obtain energy from the waste of organisms and from dead organisms (heterotrophs) No matter the type of organism, once the energy is obtained, the organic molecules enter into cellular respiration to release the energy for use B. Food Chains Sun →producer → primary consumer → secondary consumer → tertiary consumer → quaternary consumer Each level is called a trophic level or feeding level At each trophic level, decomposers break down waste and dead organisms C. Food Webs In an ecosystem, feeding relationships are rarely linear, but are branching forming a food web In a food web, some consumers can be both primary and secondary consumers, feeding at different trophic levels a. Describe a food chain with 4 trophic levels b. Describe the effects on this food web if the mouse had a toxin in it II. Energy Flow Through Ecosystems The amount of energy produced at the first trophic level limits how large the other trophic levels can get About 1% of solar energy is captured by producers to do photosynthesis About 10% of the energy stored in each trophic level is available to the next trophic levels The remaining 90% of the energy is o Used by the organisms in that trophic level o Released as heat o Lost as waste 10% 10% Sun → producer →primary →secondary consumer consumer 90% of energy in each trophic level is lost as heat, waste, or used by that trophic level A. Productivity and Biomass Biomass: the mass of the organisms in a particular trophic level Primary productivity: rate at which producers make glucose o The higher the rate, the more energy available to higher trophic levels B. Productivity and Ecological pyramids Producers set how much energy will be available to each subsequent trophic level However, only 10% of the energy of a trophic level is available to a subsequent one The rest of the energy is lost as heat, waste, or is used by the organisms in that trophic level This creates an ecological pyramid III. Chemical Cycles in ecosystems A. Basic pattern of chemical cycling Producers use chemicals from the environment Consumers eat producers incorporating some of those chemicals into themselves Decomposers break down consumers and producers returning those chemicals to the environment for producers to use B. The Carbon Cycle Producers use CO2 in atmosphere to make organic compounds (photosynthesis) Consumers eat producers and other consumers and they break down organic compounds releasing CO2 to air (cellular respiration) Dead organisms are decomposed by detrivores which release CO2 to air Volcanic eruptions and burning of fossil fuels release more CO2 into air http://www.nodvin.net/snhu/SCI219/demos/Chapter_3/Chapter_03/Present/a nimations/51_1_2_1.html C. The Nitrogen Cycle Nitrogen fixing bacteria convert N2 gas to NH4 Plants use NH4 to make protein Consumers eat plants Decomposers return NH4 to soil Some bacteria in soil recycle N2 to atmosphere http://www.classzone.com/books/ml_science_share/vis_sim/em05_pg20_nitro gen/em05_pg20_nitrogen.html D. Water Cycle Water exits plants by transpiration and becomes water vapor Water evaporates off of large bodies of water and becomes water vapor Water vapor in atmosphere condenses and precipitates down to earth to be used by plants and animals http://earthguide.ucsd.edu/earthguide/diagrams/watercycle/index.html