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Env sci lecture5

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How ecosystems work.

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Env sci lecture5

  1. 1. Chapter 5How Ecosystems Work
  2. 2. Lake Victoria Freshwater lake in Africa Formerly home to ≈ 400 species of cichlids 1960: Nile perch introduced 1990: water hyacinth invaded Today, ecological imbalance; why?
  3. 3. What Is Ecology? Literally study of one’s “house” Interactions Two components  Biotic  Abiotic Broadest biological field of study
  4. 4. Ecological Organization Organism Population Community Ecosystem Landscape Biosphere
  5. 5. Goals Of Ecologists Understand how ecosystems function Make connections: landscape ecology  Connections among ecosystems  Great blue heron
  6. 6. Energy Capacity or ability to do work Flows through ecosystems Why do organisms need energy? Different kinds Potential energy Kinetic energy
  7. 7. First Law of Thermodynamics Energy cannot be created or destroyed Energy can be changed from one form to another
  8. 8. Second Law of Thermodynamics When energy is changed from one form to another, some is degraded into heat Heat is a less usable form of energy Increases entropy in the universe
  9. 9. Ecosystem Composition Producers Consumers Decomposers
  10. 10. Producers Make their own food Photosynthesis Examples? Lii L gh gh tt e enne errg gyy 6CO2 + 6H2O + ------> C6H12O6 + 6O2
  11. 11. Consumers Feed on other things Herbivores Carnivores Omnivores Detrivores
  12. 12. Decomposers Break down dead organisms and waste products Examples?
  13. 13. Energy Flow Energy passes from one organism to the next Trophic level: each step in this flow of energy Food chain: straight path Food web  Interconnected food chains  More realistic than food chain; why?
  14. 14. Food Chain
  15. 15. FoodWeb
  16. 16. Biogeochemical Cycles Matter cycles through ecosystems Five cycles  Carbon  Hydrologic (water)  Nitrogen  Sulfur  Phosphorus
  17. 17. Carbon Cycle Essential component for life Gas (CO2) in atmosphere Several forms in ocean Can take a long time—think fossil fuels Photosynthesis Cellular respirationCO2 Sugar CO2
  18. 18. Carbon Cycle
  19. 19. Hydrologic CycleOcean Atmosphere Land Ocean
  20. 20. Nitrogen Cycle Proteins, DNA Atmosphere is 78% N2 Five steps  Nitrogen fixation  Nitrification  Assimilation  Ammonification  Denitrification
  21. 21. Nitrogen Fixation Specialized bacteria Split atmospheric nitrogen and combine it with hydrogen
  22. 22. Nitrogen Cycle
  23. 23. Sulfur Cycle Underground sedimentary rocks and minerals Erosion releases compounds to ocean Volcanoes Essential component of proteins
  24. 24. Sulfur Cycle
  25. 25. Phosphorus Cycle No atmospheric component Phosphates used in DNA and ATP (chemical energy) Phosphates move through the food chainLand Organism Organism Land
  26. 26. Phosphorus Cycle
  27. 27. Ecological Niche Everything about an organism  Adaptations  Use of resources  Lifestyle  Habitat
  28. 28. Ecological Niche Two species cannot occupy the same niche: why? Resource partitioning  Reduces niche overlap  Reduces competition
  29. 29. Resource Partitioning At Work!
  30. 30. Species Interactions No species lives in complete isolation Symbiosis  Intimate relationship between members of at least 2 species  Mutualism, commensalism, parasitism  Result of coevolution Other interactions  Predation, competition
  31. 31. Mutualism Both species benefit
  32. 32. Commensalism One species benefits, other not affected
  33. 33. Parasitism Parasite benefits, host is “harmed” Ectoparasites & endoparasites
  34. 34. Species Interactions Predation: consumption of one species by another Coevolution: “arms race”
  35. 35. Avoiding Predators Mechanical defenses Social groups Camouflage Protective chemicals
  36. 36. Species Interactions Competition: two or more organisms attempting to use the same resource Intraspecific vs. interspecific
  37. 37. Keystone Species Crucial to maintenance of an ecosystem Loss affects many other species Examples? This idea is being challenged; why?
  38. 38. Case Study: Global Climate Change Atmospheric CO2 increased dramatically. Why? 10 warmest years have occurred since 1990  2005 warmest  1998 second warmest  2002 third warmest Earth’s temperatures may rise 1.8o – 4.0o C (3.2o – 7.2o F) by end of 21st century What could occur?
  39. 39. Case Study: Global Climate Change Kyoto Protocol – International climate change conference – Kyoto, Japan 1997  Highly developed countries to cut CO2 emissions ~ 5.2% by 2012 US Department of Energy  Automotive vehicles designed for better gas mileage  High efficiency wind turbines