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  1. Ecosystems & Human Interferences

  2. Outline • The Nature of Ecosystems • Biotic Components • Autotrophs • Heterotrophs • Energy Flow • Ecological Pyramids • Global Biogeochemical Cycles • Hydrologic Cycle • Carbon Cycle • Nitrogen Cycle • Phosphorus Cycle

  3. Nature of Ecosystems • Biosphere is the organism-containing part of the • Atmosphere • Hydrosphere, and • Lithosphere • An ecosystem is a place where organisms interact with the physical environment • Ecosystems characterized by: • Cyclical flow of materials from abiotic environment through biotic community and back • One-way flow of energy

  4. Ecosystems

  5. Biotic Components:Autotrophs • Producers are autotrophs • Require only inorganic nutrients and an outside energy source to produce organic nutrients • Photoautotrophs • Chemoautrophs

  6. Biotic Components:Heterotrophs • Consumers are heterotrophs • Require a source of preformed organic nutrients • Herbivores - Feed on plants • Carnivores - Feed on other animals • Omnivores - Feed on plants and animals • Decomposers are also heterotrophs • Bacteria and fungi • Break down dead organic matter

  7. Biotic Components

  8. Energy Flow andChemical Cycling • Nutrients pass one-way through food chain from one level to another • Each level retains some energy • The rest is converted to heat, which dissipates into the environment • Chemicals cycle as organic nutrients • Once used, they are returned back to the producers by • Excretion • Death • Cellular Respiration

  9. Nature of an Ecosystem

  10. Energy Balances

  11. Grazing & Detrital Food Webs

  12. Ecological Pyramids • A trophic level • Composed of all the organisms that feed at the same level in a food chain • Only about 10% of the energy of one trophic level is useable to the next trophic level • Explains why few top carnivores can be supported in a food web

  13. Ecological Pyramid

  14. GlobalBiogeochemical Cycles • Chemical cycling may involve: • Reservoir - Source normally unavailable to producers • Fossil Fuels • Minerals • Sediments • Exchange Pool - Source from which organisms generally take chemicals • Atmosphere • Soil • Water • Biotic Community - Chemicals remain in food chains, perhaps never entering a pool

  15. Model for Chemical Cycling

  16. Hydrologic Cycle • Fresh water evaporates from bodies of water • Precipitation on land enters the ground, surface waters, or aquifers • Water eventually returns to the oceans

  17. The Hydrologic (Water) Cycle

  18. Carbon Cycle • Atmosphere is an exchange pool for carbon dioxide • The total amount of carbon dioxide in the atmosphere has been increasing every year • Thought to be due to fossil fuel combustion • Transfer Rate

  19. The Carbon Cycle

  20. Greenhouse Effect • Greenhouse gases • Carbon dioxide, nitrous oxide, methane • Allow sunlight to pass through atmosphere • Reflect infrared back to earth • Trap heat in atmosphere • If Earth’s temperature rises • More water will evaporate • More clouds will form, and • Setting up a potential positive feedback loop

  21. Earth’s Radiation Balances

  22. Nitrogen Cycle • Atmospheric nitrogen is fixed by bacteria • Make it available to plants • Nodules on legume roots • Nitrification - Production of nitrates • Denitrification - Conversion of nitrate to nitrous oxide and nitrogen gas • Balances nitrogen fixation

  23. The Nitrogen Cycle

  24. Nitrogen and Air Pollution • Acid Deposition • Nitrogen oxides and sulfur dioxide are converted to acids when they combine with water vapor • Acid rain dramatically reduces pH of surface waters in some areas • Causes heavy metals to leach out of rocks, poisoning aquatic organisms • Kills plants and causes fish to be unfit for human consumption • Smog

  25. Acid Deposition

  26. Thermal Inversion

  27. Phosphorus Cycle • Phosphorus does not enter the atmosphere • Sedimentary cycle • Phosphate taken up by producers incorporated into a variety of organic molecules • Can lead to water eutrophication • Biomagnification

  28. The Phosphorus Cycle

  29. Sources of Water Pollution

  30. Review • The Nature of Ecosystems • Biotic Components • Autotrophs • Heterotrophs • Energy Flow • Ecological Pyramids • Global Biogeochemical Cycles • Hydrologic Cycle • Carbon Cycle • Nitrogen Cycle • Phosphorus Cycle

  31. Ecosystems & Human Interferences

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