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Ecosystems Chapter 43 Ecosystem An association of organisms and their physical environment, interconnected by ongoing flow of energy and a cycling of materials Modes of Nutrition • Autotrophs – Capture sunlight or chemical energy – Producers • Heterotrophs – Extract energy from other organisms or organic wastes – Consumers, decomposers, detritivores Consumers • Herbivores • Carnivores • Parasites • Omnivores • Decomposers • Detritivores Trophic Levels • All the organisms at a trophic level are the same number of steps away from the energy input into the system • Producers are closest to the energy input and are the first trophic level Trophic Levels in Prairie 5th 4th Fourth-level consumers (heterotrophs): Top carnivores, parasites, detritivores, decomposers Third-level consumers (heterotrophs): Carnivores, parasites, detritivores, decomposers Second-level consumers (heterotrophs): 3rd Carnivores, parasites, detritivores, decomposers First-level consumers (heterotrophs): 2nd Herbivores, parasites, detritivores, decomposers Primary producers (autotrophs): 1st Photoautotrophs, chemoautotrophs Food Chain MARSH HAWK • A straight line sequence of who UPLAND SANDPIPER eats whom • Simple food chains GARTER SNAKE are rare in nature CUTWORM Food Web Energy Losses • Energy transfers are never 100 percent efficient • Some energy is lost at each step • Limits the number of trophic levels in an ecosystem Biomass Pyramid Biomass pyramid decomposers, detritivores 5 (bacteria, crayfish) third-level carnivores (gar, large-mouth bass) 1.5 1.1 second-level consumers (fishes, invertebrates) 37 first-level consumers (herbivorous fishes, turtles, invertebrates) 809 primary producers (algae, eelgrass, rooted plants) Biological Magnification A nondegradable or slowly degradable substance becomes more and more concentrated in the tissues of organisms at higher trophic levels of a food web Pyramid of Energy Flow • 10% passed on to next level top carnivores 21 carnivores herbivores 383 decomposers 3,368 producers 20,810 kilocalories/square meter/year detritivores All Heat in the End • At each trophic level, the bulk of the energy received from the previous level is used in metabolism • This energy is released as heat energy and lost to the ecosystem • Eventually, all energy is released as heat Carbon Cycle diffusion Atmosphere Bicarbonate, volcanic action carbonate Marine food TERRESTRIAL webs ROCKS Terrestrial Rocks photosynthesis Land Food Webs Soil Water Marine Sediments weathering Peat, Fossil Fuels Carbon in the Oceans • Most carbon in the ocean is dissolved carbonate and bicarbonate • Ocean currents carry dissolved carbon Carbon in Atmosphere • Atmospheric carbon is mainly carbon dioxide • Carbon dioxide is added to atmosphere – Aerobic respiration, volcanic action, burning fossil fuels • Removed by photosynthesis Greenhouse Effect • Greenhouse gases impede the escape of heat from Earth’s surface Global Warming • Long-term increase in the temperature of Earth’s lower atmosphere Carbon Dioxide Increase • Carbon dioxide levels fluctuate seasonally • The average level is steadily increasing • Burning of fossil fuels and deforestation are contributing to the increase Other Greenhouse Gases • CFCs - synthetic gases used in plastics and in refrigeration • Methane - produced by termites and bacteria • Nitrous oxide - released by bacteria, fertilizers, and animal wastes Effects of Global Warming • Global Climate Changes = More Storms & More Violent Storms • Drought & Regional Weather Changes • Melting of Glaciers and Polar Ice Caps • Rise in Sea Level
