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Ecosystems Energy Flow 2. Chemical cycles water, carbon, nitrogen 3. Human effects on cycles

Ecosystems Energy Flow 2. Chemical cycles water, carbon, nitrogen 3. Human effects on cycles eutrophication, acid rain. Ecosystem = community plus abiotic factors - Conditions (temp, light) Resources (water, nutrients)

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Ecosystems Energy Flow 2. Chemical cycles water, carbon, nitrogen 3. Human effects on cycles

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  1. Ecosystems Energy Flow 2. Chemical cycles water, carbon, nitrogen 3. Human effects on cycles eutrophication, acid rain

  2. Ecosystem = community plus abiotic factors - Conditions (temp, light) Resources (water, nutrients) • Energy flows from the sun, through plants, animals, and decomposers, and is lost as heat • Chemicals are recycled between air, water, soil, and organisms

  3. A terrarium ecosystem / Biosphere II Chemical cycling(C, N, etc.) Chemicalenergy Heatenergy Lightenergy Figure 36.8

  4. Wastes anddead organisms Tertiaryandsecondaryconsumers Food webs Secondaryandprimaryconsumers Primaryconsumers Producers Detritivores (Plants, algae,phytoplankton) (Prokaryotes, fungi,certain animals) Figure 36.10

  5. DDT concentration:increase of10 million times DDT infish-eating birds25 ppm • Chemicals are concentrated in food chains by biological magnification DDT inlarge fish2 ppm DDT insmall fish0.5 ppm DDT inzooplankton0.04 ppm DDT in water0.000003 ppm Figure 38.3B

  6. Energy supply limits the length of food chains • Food chains/webs reveal the flow of energy • 170 billion tons of biomass per year Avg. 10% conversion of biomass to next level Tertiaryconsumers 10 kcal Secondaryconsumers 100 kcal Primaryconsumers 1,000kcal Endothermic animals convert only 2% Producers 10,000 kcal Plants convert 30-85% 1,000,000 kcal of sunlight Figure 36.11

  7. Consequences: • Low density of large carnivores • a field of corn can support more vegetarians than carnivores. TROPHIC LEVEL Secondaryconsumers Humanmeat-eaters Cattle Primaryconsumers Humanvegetarians Corn Corn Producers Figure 36.12

  8. Chemicals are recycled between organic matter and abiotic reservoirs • Water cycle - Carbon cycle • Nitrogen cycle

  9. Solar heat Net movementof water vaporby wind (36) Water vaporover the land Water vaporover the sea Evaporationandtranspiration(59) Precipitationover the land(95) Precipitationover the sea(283) Evaporationfrom the sea(319) Oceans Surface waterand groundwater Flow of waterfrom land to sea(36) Figure 36.14

  10. salt water = 97.5% freshwater = 2.5% lakes, rivers, and soil 0.03% ice caps and glaciers 1.97% atmosphere 0.001% ground- water 0.5% oceans

  11. Carbon cycle • Carbon is taken from the atmosphere by photosynthesis • used to make organic molecules returned to the atmosphere by cellular respiration, decomposers

  12. CO2 in atmosphere Plants,algae,cyanobacteria Cellular respiration Burning Photosynthesis Higher-levelconsumers Primaryconsumers Wood andfossil fuels Decomposition Detritivores(soil microbesand others) Detritus Figure 36.15

  13. The nitrogen cycle relies heavily on bacteria • Nitrogen is plentiful in the atmosphere as N2 • But plants and animals cannot use N2 • Some bacteria in soil and legume root nodules convert N2 to compounds that plants can use: ammonium (NH4+) and nitrate (NO3–)

  14. Nitrogen (N2) in atmosphere Amino acidsand proteins inplants and animals Assimilationby plants Nitrogenfixation Denitrifyingbacteria Detritus Nitrogen-fixingbacteria in rootnodules of legumes Nitrates(NO3–) Detritivores Nitrogen-fixingbacteria in soil Decomposition Nitrifyingbacteria Nitrogenfixation Ammonium (NH4+)

  15. Human impact on chemical cycles 76% naturally occurring 24% human- caused 24% naturally occurring 58% human- caused 46% available 54% used Atmospheric CO2 concentration Terrestrial nitrogen fixation Accessible surface water

  16. Example: acid rain • Sulfur dioxide, nitrogen oxides create strong acids when dissolved in rain water. • Low pH kills aquatic life, leaches nutrients from soil • Calcium deficiency affects everything in food chain: plants, insects, birds. Weak egg shells. • Environmental changes caused by humans can unbalance nutrient cycling over the long term

  17. eutrophication • Algal bloom can cause a lake to lose its species diversity

  18. Human-caused eutrophication wiped out fisheries in Lake Erie in the 1950s and 1960s • classic experiments on eutrophication led to the ban on phosphates in detergents Figure 36.19B

  19. What are the limits to human alteration of chemical cycles and habitats? • What should the limits be? • How do we set priorities for what we value in the natural world? Aesthetic, economic, conservation, humans

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