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Chapter 5 How Ecosystems Work

Chapter 5 How Ecosystems Work. 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?.

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Chapter 5 How Ecosystems Work

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  1. Chapter 5How Ecosystems Work

  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. What Is Ecology? • Literally study of one’s “house” • Interactions • Two components • Biotic • Abiotic • Broadest biological field of study

  4. Ecological Organization • Organism • Population • Community • Ecosystem • Landscape • Biosphere

  5. Goals Of Ecologists • Understand how ecosystems function • Make connections: landscape ecology • Connections among ecosystems • Great blue heron

  6. Energy • Capacity or ability to do work • Flows through ecosystems • Why do organisms need energy? • Different kinds Potential energy Kinetic energy

  7. Two Important Laws • First law of thermodynamics • Energy cannot be created or destroyed • Energy can be changed from one form to another

  8. Two Important Laws • 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. Ecosystem Composition • Producers • Consumers • Decomposers

  10. Light energy Producers • Make their own food • Photosynthesis • Examples? 6CO2 + 6H2O + ------> C6H12O6 + 6O2

  11. Consumers • Feed on other things • Herbivores • Carnivores • Omnivores • Detrivores

  12. Decomposers • Break down dead organisms and waste products • Examples?

  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. Food Chain

  15. Food Web

  16. Biogeochemical Cycles • Matter cycles through ecosystems • Four cycles • Hydrologic (water) • Carbon • Nitrogen • Phosphorus

  17. Ocean Atmosphere Land Ocean Hydrologic Cycle

  18. Photosynthesis Cellular respiration CO2 Sugar CO2 Carbon Cycle • Essential component for life • Gas (CO2) in atmosphere • Several forms in ocean • Can take a long time—think fossil fuels

  19. Carbon Cycle

  20. Nitrogen Cycle • Proteins, DNA • Atmosphere is 78% N2 • Five steps • Nitrogen fixation • Nitrification • Assimilation • Ammonification • Denitrification

  21. Roots of a pea plant Nostoc Nitrogen Fixation • Specialized bacteria • Split atmospheric nitrogen and combine it with hydrogen

  22. Nitrogen Cycle • Nitrification: ammonia converted to nitrate • Assimilation: plants or animals taking in nitrates • Ammonification: organisms produce nitrogen-containing wastes • Denitrification: nitrate converted back to nitrogen gas • Different bacteria perform these steps

  23. Nitrogen Cycle

  24. Land Organism Organism Land Phosphorus Cycle • No atmospheric component • Phosphates used in DNA and ATP (chemical energy) • Phosphates move through the food chain

  25. Phosphorus Cycle

  26. Ecological Niche • Everything about an organism • Adaptations • Use of resources • Lifestyle • Habitat

  27. Ecological Niche • Two species cannot occupy the same niche: why? • Resource partitioning • Reduces niche overlap • Reduces competition

  28. Resource Partitioning At Work!

  29. 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

  30. Mutualism • Both species benefit

  31. Commensalism • One species benefits, other not affected

  32. Parasitism • Parasite benefits, host is “harmed” • Ectoparasites & endoparasites

  33. Species Interactions • Predation: consumption of one species by another • Coevolution: “arms race”

  34. Avoiding Predators • Mechanical defenses • Social groups • Camouflage • Protective chemicals

  35. Species Interactions • Competition: two or more organisms attempting to use the same resource • Intraspecific vs. interspecific

  36. Keystone Species • Crucial to maintenance of an ecosystem • Loss affects many other species • Examples? • This idea is being challenged; why?

  37. Case Study: Global Warming • Greenhouse effect • Natural effect • Occurs when greenhouse gases trap heat in the atmosphere • Without the greenhouse effect, earth would be much colder • CO2 is a major greenhouse gas • Where is it coming from?

  38. Case Study: Global Warming • What should be done? • Kyoto Protocol • Developed countries must cut greenhouse gas emissions • What did the U.S. do? • Other solutions?

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