Chapter 21: Ecosystem Energetics Flashcards
This law states that energy is neither created nor destroyed.
First law of thermodynamics
This law states that when energy is transferred or transformed, part of the energy assumes a form that cannot pass on any further.
Second law of thermodynamics
A chemical reaction that results in the loss of energy from the system is an ___ reaction.
exothermic
A chemical reaction that must absorb energy to proceed is an ___ reaction.
endothermic
A reduction in potential energy is called ___.
entropy
True or false: The flow of energy through a terrestrial ecosystem starts with harnessing of sunlight by autotrophs.
True
The rate at which radiant energy is converted by photosynthesis to organic compounds is referred to as ___.
primary productivity
The total rate of photosynthesis, or energy assimilated by autotrophs, is the ___.
gross primary productivity
The rate of energy storage as organic matter after respiration is called ___.
net primary productivity
Net primary = gross primary - respiration by autotrophs
Yup
What unit is productivity usually expressed as?
units of energy per unit area per unit time
The amount of accumulated organic matter found in an area at a given time is the ___.
standing crop biomass
Net primary productivity = NPP
Kay
SCB = standing crop biomass
Kay
NPP = ΔSCB + D + C
D is death of plants (loss of biomass) and C is loss of biomass due to consumption by organisms
NPP ___ with increasing rainfall and temperature.
increases
Temperature, water, and nutrients control primary production in ___ ecosystems.
terrestrial
Temperature, light, and nutrients control primary production in ___ ecosystems.
aquatic
Photosynthesis changes with water depth, but ___ does not.
Respiration
The depth at which the availability of light is equal to the light compensation point is called the ___.
compensation depth
At compensation depth, the rate of photosynthesis is ___ than rate of respiration, and NPP is ___.
equal to; zero
Organic carbon produced within an ecosystem is called ___ carbon.
autochthonous
Carbon that comes from outside an ecosystem is called ___ carbon.
allochthonous
In small, shaded streams where not a lot of photosynthesis can happen, ___ carbon is very important.
allochthonous
Net energy of production is called ___.
secondary production
Secondary production per unit time is referred to as ___.
secondary productivity
The ratio of assimilation to ingestion is called ___ and is a measure of the efficiency with which the consumer extracts energy from food.
assimilation efficiency
The ratio of production to assimilation is called ___ and is a measure of how efficiently the consumer incorporates assimilated energy into secondary production.
production efficiency
True or false: consumers vary in efficiency of production.
True
True or false: Bigger, more complex organisms have higher production efficiency.
False. Invertebrates have the highest, actually.
In this food chain, the source of energy is living plant biomass or net primary production.
Grazing food chain
In this food chain, the source of energy is dead organic matter.
Detrital food chain
In the grazing food chain, flow of energy between trophic levels is ___, while in the detrital food chain it is not.
unidirectional
True or false: the energy available to a given trophic level is the production of the next lower level (n-1).
True
The ratio of ingestion to production at the next lower trophic level is called the ___.
consumption efficiency
Values of consumption efficiency for the various consumer trophic levels determine the pathway of energy flow through the food chain, providing a basis for comparison of energy flow through different ecosystems.
Ok.
A measure of efficiency used to describe the transfer of energy between trophic levels is called the ___.
trophic efficiency
This is the ratio of productivity in a given trophic level to the trophic level it feeds on.
trophic efficiency
Decreasing energy transfers through the food web causes a ___ in the standing biomass of organisms within each successive trophic level.
decrease
What are the two types of biogeochemical cycles?
gaseous and sedimentary
Nutrients entering the ecosystem via rainfall is called ___.
wetfall
Nutrients brought in by particles and aerosols are called ___.
dryfall
Nutrients for ___ ecosystems enter via drainage water, detritus, and sediment.
aquatic
Fires and harvesting are examples of ___ that result in loss of nutrients from the ecosystem.
outputs
True or false: the output of one system can be the input of another.
True
The difference between the rate of carbon uptake in photosynthesis and the rate of carbon loss due to autotrophic and heterotrophic respiration is the ___.
net ecosystem productivity
Why do levels of atmospheric carbon dioxide drop in the spring?
Because the plants are using it all.
True or false: atmospheric nitrogen can be taken up by plants.
False
One method for nitrogen to enter ecosystems is ___.
nitrogen fixation
Microbial decomposition of organic matter, in which NH3 is released as a waste product of microbial activity and NH4 occurs in the soil as a product of microbial decomposition of organic matter, occurs in a process called ___.
ammonification
Oxidizing NO2 to NO3 is called ___.
nitrification
This can occur under anaerobic conditions and is when NO3 is reduced to N2O or N2.
denitrification
