Chapter 20 Flashcards
Most energy that moves through ecosystems originates as…
solar energy that powers photosynthesis.
chemosynthesis
Where sunlight is not available (e.g., deep ocean thermal vents), producers rely on chemosynthesis as their source of energy.
Primary productivity
the rate at which solar or chemical energy is captured and converted into chemical bonds by photosynthesis or chemosynthesis.
Standing crop
the biomass of producers present in a given area of an ecosystem at a particular moment in time.
Ecosystems with high primary productivity…
may not have a high standing crop; consumers may eat it as quickly as it grows.
Gross primary produc-vity (GPP)
the rate at which energy is captured and assimilated by producers in an area.
Net primary produc-vity (NPP)
the rate of energy that is assimilated by producers and converted into producer biomass in an area; includes all energy that is not respired
NPP =
GPP - Respiration
GPP =
NPP + Respiration
In aquatic systems, measuring CO2 does not provide a good estimate of NPP because…
CO2 is rapidly converted into bicarbonate ions.
Remote sensing
a technique that allows measurement of conditions on Earth from a distant location, typically using satellites or airplanes that take photographs of large areas of the globe.
Chlorophyll pigments absorb wavelengths in the red and blue range but reflect wavelengths in the green range.
Satellite images that show a pattern of high absorption of blue and red light, and high reflectance of green light indicate ecosystems with high standing crops.
Egested energy
the portion of consumed energy that is excreted or regurgitated.
Assimilated energy
the portion of energy that a consumer digests and absorbs; analogous to GPP for producers.
Respired energy
the portion of assimilated energy a consumer uses for respiration; remaining energy can be used for growth and reproduction (i.e., net secondary productivity).
Net secondary productivity
the rate of consumer biomass accumulation in a given area; analogous to NPP for producers.
Trophic pyramid
a chart composed of stacked rectangles represen=ng the amount of energy (i.e., pyramid of energy) or biomass (i.e., pyramid of biomass) in each trophic group.
Consumption efficiency
the percentage of energy or biomass in a trophic level that is consumed by the next higher trophic level.
consumption coefficient=consumed energy (J)/net production energy of the next lower trophic level (J)
Assimilation efficiency
the percentage of consumed energy that is assimilated (i.e., material that is not egested, such as bones).
assimilation efficiency=assimilated energy (J)/consumed energy (J)
primary consumers tend to have ___________ efficiencies than secondary consumers because prey tissues are more digestible than plant tissues.
lower
Net production efficiency
the percentage of assimilated energy that is used for growth and reproduction; the percentage of assimilated energy that remains ager respiration.
net production efficiency= net production energy (J)/assimilated energy (J)
Ecological efficiency (food chain efficiency)
the percentage of net production from one trophic level compared to the next lower trophic level.
ecological efficiency= net production energy on a trophic level (J)/net production energy of the next lower trophic level (J)
Because energy is lost at each of these steps, ecological efficiency is usually low, ranging from 5% to 20%; ___ is used as a rule of thumb.
10%
Energy residence time
the length of time that energy spends in a given trophic level; the longer the residence time, the greater the accumulation of energy in that trophic level.
Biomass residence time
the length of time that biomass spends in a given trophic level.
Ecological stoichiometry
the study of the balance of nutrients in ecological interactions, such as between an herbivore and a plant.
The nutrients that a species requires depends on its biology.
If the ratio of ingested nutrients to required nutrients is low, consumers must…
eat more food
