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Chapter 54 – Ecosystems

Chapter 54 – Ecosystems. Energy and Nutrient Dynamics. Trophic structure / levels - feeding relationships in an ecosystem Primary producers - the trophic level that supports all others; autotrophs Primary consumers - herbivores Secondary and tertiary consumers - carnivores

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Chapter 54 – Ecosystems

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  1. Chapter 54 – Ecosystems

  2. Energy and Nutrient Dynamics • Trophic structure / levels - feeding relationships in an ecosystem • Primary producers - the trophic level that supports all others; autotrophs • Primary consumers - herbivores • Secondary and tertiary consumers - carnivores • Detrivores/detritus - special consumers that derive nutrition from non-living organic matter • Food chain - trophic level food pathway

  3. Energy Flow • Primary productivity - amount of light energy converted to chemical energy by autotrophs during a given time period, usually expressed as biomass • Gross (GPP): total energy • Net (NPP): represents the storage of energy available to consumers • R: respiration • NPP = GPP - R • Biomass - primary productivity reflected as dry weight of organic material

  4. Energy Transfer • Ecological efficiency - % of E transferred from one trophic level to the next (5-20%) • Secondary productivity - the rate at which an ecosystem's consumers convert chemical energy of the food they eat into their own new biomass • Production efficiency (measure of energy transformation) = net secondary production / assimilation of primary production (portion of energy stored in food not used for respiration); basically the fraction of energy stored in food that is not used for respiration • Birds and mammals have low production efficiencies = 1-3% • Fish = 10% • Insects = 40% (see example) Example: 33 J (approx. 1/6th) of plant is used for secondary production or growth. Has 33% production efficiency; 67 J of 100 J used for respiration

  5. Ecological Pyramids

  6. Ecological Pyramids • Trophic efficiency – percentage of production transferred from one trophic level to the next • Pyramid of net production – shows loss of energy from each trophic level • Biomass pyramid – represents standing crop in each trophic level • Pyramid of numbers • Green world hypothesis Pyramid of net production Pyramid of numbers Biomass pyramid

  7. Biogeochemical Cycles

  8. Biogeochemical Cycles (cont.)

  9. Human Impact • Nutrient enrichment • Nitrogen contamination by agriculture • Eutrophication of aquatic ecosystems • Acid precipitation • from burning of wood, coal, and other fossil fuels • Toxins/Biological magnification • Humans dump toxins into environment • Tend to concentrate at higher trophic levels (example PCBs) • Atmospheric CO2 • as CO2 increases, global temperature increases; global warming • Ozone Depletion • resulting from an accumulation of chlorofluorocarbons (CFCs) from refrigeration units, aerosol cans, and manufacturing processes • Rainforest Depletion

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