Post on 30-Dec-2015
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• Chapter 55 – Ecosystems
Energy and Nutrient DynamicsEnergy 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
Energy FlowEnergy 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
Energy TransferEnergy 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
Ecological PyramidsEcological 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
Biogeochemical CyclesBiogeochemical Cycles
Biogeochemical Cycles (cont.)Biogeochemical Cycles (cont.)
Human Impact - NegativeHuman 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
Human Impact - PositiveHuman 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