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11-19-09 - Biology 330 Class Notes Note Not all energy...

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Biology 330 – Class Notes – 11/19/09 Note : Not all energy makes it from one trophic level to the next (a lot is lost say from primary producer to secondary producer) Consumption efficiency Low because not all green biomass is digestible - Assimilation efficiency - Higher the cellulose content, the lower the assimilation efficiency Production efficiency – how well the organism takes the energy absorbed/assimilated and uses it for growth QUESTION : How many times can you pass off energy in order to sustain the population Detritus – dead organic matter – consumed by microorganisms and detritivores Gross primary production – grasses 90.7% of the energy is passed on to dead organic matter. Figure 3 – Energy flow through a generalized lake pelagic zone. Finely striped arrows show consumption or death. Numerical (2/3) of energy from phytoplankton is transferred to dead organic matter (1/3) of energy is passed on to the next trophic level Detrital pathway is the DOMINANT energy pathway in all ecosystems. In the fall, dead leaves in the stream are slowly colonized by bacteria Stream insects eat the leaves in order to get the protein found in the microorganisms on the leaf This is what keeps stream ecosystems going o There is thus an energetic subsidy from terrestrial canopy These leaves sequentially decompose
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If we are going to use pyramids to model trophic levels, we need to use energy as the unit of measure. This many measured income solar radiation: 1,1888,720 kcal/m^2/yr o Energy on the lake Measured primary productivity: o Gross primary production: 1,113 kcal/m^2/yr Efficiency: 0.10% and Respiration losses: 21%
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