1. Chapter 55 – 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 Detritivores/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. 1/6 th ) of plant is used for secondary production or growth. Has 33% production efficiency; 67 J of 100 J used for respiration

5. 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 numbers Pyramid of net production Biomass pyramid

6. Biogeochemical Cycles

7. Biogeochemical Cycles (cont.)

8. Human Impact - Negative 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

9. Human Impact - Positive Restoration Ecology – goal to initiate or speed up the recovery of degraded ecosystems –Bioremediation: using organisms to detoxify polluted ecosystems –Biological Augmentation: using organisms to add essential materials to a degraded ecosystem