Energy Flow

***The following notes are taken directly from –Primary Production and Energy Flow, Chapter 18 of  Ecology:  Concepts and Applications, 5th edition, by Manuel C. Molles Jr.***


*The interactions between organisms and their environments are fueled by complex fluxes and transformations of energy.
*Primary Production is the production of new organic matter, or biomass, by autotrophs of an ecosystem.

*An autotroph is any organism capable of self-nourishment by using inorganic materials as a source of nutrients and using photosynthesis or chemosynthesis as a source of energy. –Most plants and certain bacteria and protists are autotrophs.

*The rate of primary production is the amount of biomass produced over some interval of time.

*Biomass is the mass of living biological organisms in a given are

*Gross primary production is the total amount of biomass produced by all the autotrophs in the ecosystem at a given time.

*Net Primary production is the amount of biomass left over after autotrophs have met their own energetic needs.

*A trophic level is a position in a food web and is determined by the number of transfers of energy from primary producers to that level.

*Terrestrial primary production is generally limited by temperature and moisture.

*Actual evapotraspiration (AET) is the total amount of water that evaporates and transpires off a landscape during the course of a year and is measureD in millimeters of water per year.

*Ecosystems show low levels of AET either because they receive little precipitation, are very cold, or both; these ecosystems will have lower primary production than ecosystems with higher levels of AET.

*Aquatic primary production is generally limited by nutrient availability.

*Consumers can influence rates of primary production in aquatic andterrestrial ecosystems through trophic cascades.

*A trophic cascade is the effects of consumers coming from the top of food webs to the base.  The cascade involves effects of predators on prey that alter abundance, biomass, or productivity of a population, community, or trophic level across more than one link in the food web.

*Each transfer of conversion of energy within the foodweb results in some loss of energy. This being the case, energy losses limit the number of trophic levels in an ecosystem.

*Trophic dynamics is the transfer of energy from one part of an ecosystem to another

*Ecological efficiency is the percentage of energy in the biomass at a lower trophic level that is transferred to the next higher trophic level.


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