Biology Lecture 24: Ecosystem Ecology
A few terms:
o Community: all of the organisms living in some defined place
o Ecosystem: a biotic community and its abiotic environment functioning as a system
o Ecosystems are open systems (not closed)
2 major activities in ecosystems: production, consumption:
o Production: new biomass is being created from inorganic substances
o Consumption: previously created biomass is being converted to new forms of biomass
o 4 major components:
Producers (autotrophs): make their own food (usually from the sun)
Consumers (heterotrophs): everything that has to eat something else (this
Where does the energy come from?
o In most ecosystems energy comes from the sun (light energy)
Photoautotroph's utilize this light energy to create biomass (creating energy by
o Chemoautotrophs depend on chemical energy to produce biomass (occurs when the
sun is not present to produce energy)
o Any chemical element that is needed for living things to grow or reproduce
Organic or inorganic:
Organic simply means carbon containing (exception of2CO , carbonate)
Micronutrients: something that organisms need in small quantities (Ex: iron)
Macronutrients: something that an organism needs a lot of (Ex: oxygen)
o Nutrient sources: geological sources (mineral soil), atmospheric sources, oceans,
decomposition & nutrient cycling
Energy flows up the food web...:
o Energy flows from sources through primary produces through consumers and
Ecological inefficiency: some energy is lost at each transfer between levels
Energy constantly being replaced from outside the ecosystem
Ecological efficiency <100%:
o Harvesting efficiency: the portion of available food that is consumed (always <100%)
o Assimilation of efficiency: the proportion of energy consumed that is assimilated or
digested (always <100%)
o Production efficiency: the portion of energy assimilated or digested that becomes new
tissue (always <100%) Clicker Question: On average, how much energy contained in a given trophic level is available for
the next higher trophic level?
A. About 90%
B. About 50%
C. About 10%
Clicker Question: Which of the following humans is at the highest trophic level?
A. Alice, who eats plants.
B. Betty, who eats mostly alligator steaks.
C. Cameron, Betty's baby, who e