1. Ecosystems & Human Interferences Chapter 48

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

3. Ecosystems & Human Interferences 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. 4 Ecosystems

5. Ecosystems & Human Interferences 5 Biotic Components: Autotrophs Producers are autotrophs RRRRequire only inorganic nutrients and an outside energy source to produce organic nutrients PPPPhotoautotrophs CCCChemoautrophs

6. Ecosystems & Human Interferences 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. 7 Biotic Components

8. Ecosystems & Human Interferences 8 Energy Flow and Chemical 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. 9 Nature of an Ecosystem

10. 10 Energy Balances

11. 11 Grazing & Detrital Food Webs

12. Ecosystems & Human Interferences 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. 13 Ecological Pyramid

14. Ecosystems & Human Interferences 14 Global Biogeochemical 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. 15 Model for Chemical Cycling

16. Ecosystems & Human Interferences 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. 17 The Hydrologic (Water) Cycle

18. Ecosystems & Human Interferences 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. 19 The Carbon Cycle

20. Ecosystems & Human Interferences 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. 21 Earth’s Radiation Balances

22. Ecosystems & Human Interferences 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. 23 The Nitrogen Cycle

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

25. 25 Acid Deposition

26. 26 Thermal Inversion

27. Ecosystems & Human Interferences 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. 28 The Phosphorus Cycle

29. 29 Sources of Water Pollution

30. Ecosystems & Human Interferences Global Climate Change The average temperature in the U.S. has risen since 1901. The warmest decade on record was 2000-2009. With the increase in temperature, there have also been increases in drought conditions in some areas, and increased precipitation in other areas, increase in sea level. U.S. produced greenhouse gas emissions have increased by 14 percent from 1990-2008. Since global climate change effects the entire world population, global cooperation is required in order to solve the problems at hand. 30

31. Ecosystems & Human Interferences Global Climate Change The Kyoto Protocol, which has been enforced since 2005, has the goal to achieve stabilization and reduction of greenhouse gas concentrations. The United States has not ratified the agreement. The Copenhagen conference in 2009 did not create any binding agreement for long term action against climate change. One of the outcomes of this conference was the commitment to raise money to help poor countries cope with the effects of climate change. The Cancun summit in 2010 solidified the agreement to raise funds to help poor countries defend against climate change 31

32. Ecosystems & Human Interferences Ending Slide Chapter 48