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Ch 55 ecosystems
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Ch 55 ecosystems


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Ecosystems ppt based on Ch 55 in 8th edition of Biology, by Campbell and Reece

Ecosystems ppt based on Ch 55 in 8th edition of Biology, by Campbell and Reece

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  • Every day the earth is bombarded by 10^22 J of solar light
  • GPP is often about ½ of GPP
  • Primary producers only about 1% efficient
  • Anything that is taken into the body faster than it breaks down / gets expelled will accumulate. Some things are never expelled. Bioaccumulation occurs within a trophic level. Environmental persistence (does not break down) helps substance accumulate. Persistant Organic Pollutants (POPs) – we lack the enzymes to break them down, as they are relatively new to the world. Metals cannot degrade (they are elements) Eagles have recovered after the ban of DDT usage. Common in aquatic food chains (direct absorption). Algae absorb mercury (Methyl Mercury), only excrete slowly.
  • PCBs were used commercially since 1929 as coolants and lubricants, banned in 1976 in USA Lake Trout were as high as 24 ppm in the 1970s Water in 1994 ranged from 0 – 0.36 parts per trillion (0.000000 36 ppm) Source:
  • Halocarbons are also about 14% of the greenhouse gas warming effect (radiative forcing) CFCs last 50+ years in atm Skin cancer, plant DNA damage Montreal Protocol : 190 nations in 1987 regulate these gases Ozone depletion has stabilized Expected to be at pre-1980 levels by 2075!
  • Transcript

    • 1. Ch 55 Ecosystems Jeff Jewett ACS June 2010 Ver 1
    • 2. Ecosystem
      • Sum of all organisms in an area AND all the abiotic factors with which they interact
      • Communities PLUS abiotic factors
      • Boundaries are rarely clear-cut, may depend on scale of question
    • 3. Ch 55 Key Topics
      • Conservation of Energy/Mass
      • GPP/NPP and limitations
      • Energy Transfer  pyramids of energy/biomass
      • Biogeochemical Cycles (C, N, H 2 0)
      • Human impact on biogeo. Cycles
        • Global warming, eutrophication, biomagnification, acid rain, ozone hole
    • 4. Energy Flows, Matter Cycles
      • Energy enters (usually as sunlight)
      • Converted to biomass (chemical energy) by autotrophs
      • Passed to heterotrophs (incl. decomposers)
      • Dissipated as heat
    • 5. Energy Flows, Matter Cycles (2)
      • Chemical elements (C, N, P) are cycled between abiotic and biotic parts of ecosystem (Law of Conservation of Mass)
      • Matter continuously cycles (not created or destroyed)
      • 2 nd law of Thermodynamics:
      • Energy conversions are never 100% efficient, therefore some is always lost as heat
      • Ecosystems require constant input of energy
    • 6. Trophic Levels
      • Autotrophs = primary producers (redundant)
        • Photoautotrophs rely on light for energy (by FAR the most common)
        • Chemoautotrophs oxidize naturally occuring inorganic compounds as fuel (common in hot springs, deep-sea volcanic vents)
      • All of the ecosystem depends on autotrophs!
    • 7. Trophic Levels (2)
      • Heterotrophs
        • depend directly or indirectly on autotrophs
        • eat things that are alive or were alive
        • Consumers & decomposers (detritivores)
        • Detritivores – fungus, bacteria, insects (FBI) eat detritus (non-living organic material such as feces, dead critters, fallen leaves, wood)
        • Consumers – primary, secondary, tertiary, quarternary (higher levels rare)
    • 8.
    • 9. 55.2 Energy GPP
      • Gross Primary Production (GPP) = Amount of light energy converted to chemical energy (sugars) per time (rate of photosynthesis)
      • Some of this energy is used by the plant for life (cellular respiration)
      • Some is converted into biomass, such as starch storage or structural components (new growth)
    • 10. NPP – a very important ecological statistic!
      • Net Primary Productivity – amount of sugars left over after respiration, per unit time (rate of new biomass production)
      • NPP = GPP – R
      • Value of NPP gives the size of the base of the food chain (how much total food is there for consumers?)
      • NPP highest where it is warm/wet
      • (tropical rainforest)
    • 11. Global NPP, 2008 NASA Earth Observatory:
    • 12. June NPP
    • 13. December NPP
    • 14. Human Appropriation of NPP
    • 15. Aquatic NPP Limitation
      • Light - <50% of light below 15m (photic zone)
      • Nutrient Limitation (more important) – Nitrogen or Phosporus, tend to sink, rapid uptake by phytoplankton, Iron too
      • Nutrient limitation leads to high NPP in river deltas or areas with upwelling
    • 16. Terrestrial NPP
      • Usually limited by heat or water
      • Evapotranspiration is how much water is evaporated from land and transpired from plants (driven by heat and precipitation)
    • 17. Limiting Nutrient
      • A nutrient that when added to an ecosystem increases NPP
      • Most often N, P (that’s what in fertilizer!), same as aquatic
    • 18. Pyramids!
      • Numbers
      • Biomass
      • Energy
    • 19. Pyramid of Net Production
      • Rule of 10 : only about 10% of the energy is passed up each trophic level
    • 20. Biomass
      • Dry mass of all living material in an area
      • How do you calculate? (Hard)
        • Cut everything, dry it, mass it (below ground very tricky)
        • Measure everything, estimate volume, estimate mass
        • Secondary measures like ocean fish harvest
    • 21. Biomass Pyramid Why do some people eat a vegetarian diet for environmental reasons?
    • 22. Biogeochemical Cycles
      • Energy flows, matter cycles!!!
      • Carbon, Nitrogen, Phosphorus, Water
    • 23. Nitrogen Cycle
      • 80% of atm is N 2 , but this inorganic form is not available to eukaryotes
      • Plants use “organic” NH 4 + (ammonium) and NO 3 - (nitrate)
    • 24.
      • Humans have more than doubled “organic”/fixed N supply!!!
      • Fertilizers, combustion, tillage practices, deforestation, legume cultivation all increase fixed N supply
      • Acid rain/deposition, algal blooms, ecosystem changes
    • 25. Harmful Algal Bloom (“Red Tide”) Photo credit: NOAA:
    • 26. Eutrophication: Spring phytoplankton bloom off New Zealand Photo courtesy NASA Earth Observatory
    • 27. Eutrophication Lake Valencia, Venezuala NASA Earth Observatory:
    • 28. Decomposers recycle nutrients
      • Heterotrophs
      • Saprotrophs (old term): eat dead/dying organisms
      • Fungi, Bacteria, Insects
      • Fungi can digest lignin, so main forest decomposers
    • 29. Eutrophication
      • Nutrient addition (P in inland lakes, N offshore) from sewage, agricultural run-off, detergents, fertilizers
      • Lead to temporary algal bloom
      • Algal die-off leads to massive bloom in decomposing bacteria
      • Bacteria consume all dissolved O 2
      • Fish kills 
    • 30. Fish Kill at the Salton Sea, CA Image from Encyclopedia of Earth:
    • 31. Eutrophication, continued
      • Reduce seagrasses (loss of light)
      • Cascading food web effects  loss of fish/shellfish that depend on seagrasses
      • Some algal blooms are toxic
      • Riparian/wetland buffers help (no more straight rivers!)
      • Don’t over-apply fertilizer
      • “ Precision Agriculture”
      • Reduce livestock densities
    • 32. Biomagnification
      • Long-lived (persistent), fat-soluble molecules build up in organism ( bioaccumulation)
      • Concentration of these fat soluble substances increase as you go up trophic levels  biomagnification!
      • DDT, PCBs (“Persistent Organic Pollutants” or POPs)
      • Mercury & other metals
      • Biomagnification Animation
    • 33. Great Lakes Population
    • 34. Great Lakes Biomagnification Peak water PCB concentation in 1994: 0.00000036 ppm Bioaccumulation of 69,000 X Herring Gulls have 3.4 MILLION times more PCB than the water!
    • 35. Ozone O 3
      • Bad down low (smog), good up high
      • Blocks UV radiation in stratosphere (17-25km up)
      • More UV  skin cancer, cataracts,
      • Decrease up to 50% in Antarctica, up to 10% in mid-latitudes
      • NASA animation
    • 36. Atmospheric (Stratospheric) Ozone Depletion