Ecosystem energetics Flashcards
What are ecosystems?
communities of organisms that interact with their physical environment under the influence of environmental factors
what is ecosystem energetics?
study of how energy is fixed by autotrophs (plants) and made available to heterotrophs (consumers)
What is energy often measured as?
biomass, the dry weight of organic matter in an organism or ecosystem
What are primary producers?
autotrophic organisms (in the first trophic level) that fix inorganic nutrients (CNPO) into organic molecules
they carry out primary production
what is primary productivity?
the rate at which energy is fixed to organic molecules (ecosystem quality)
what is gross primary productivity?
total amount of energy fixed into organic molecules in an ecosystem
what is net primary production?
what producer makes minus what it uses for itself (Ermr,Eactivity)
it is the amount of energy needed for growth, Measured as biomass
Tells us how much energy is available to other trophic levels
What factors affect primary productivity?
Light
temp
precipitation
nitrogen
phosphorus
How does light affect primary productivity?
Low light, low productivity
More light, more productivity until it reaches plateau (enzymes are limited by other factors)
Too much light reduces/decreases productivity (because of radiation)
How does temp affect primary productivity?
Enzymes work faster at higher temp, so more productivity
How does precipitation affect primary productivity?
regular amount of precipitation, increase in Production
Too much precipitation (less light, flooding, leaching of N), decrease in production
How does nitrogen affect primary productivity?
N increases PP
Nitrogen is soluble and easily washed away, so it’s limited on land
Not as limiting in aquatic environments
How does phosphorus affect primary productivity?
P increases PP
Occurs in insoluble forms, so it stays on land
More limiting in aquatic environments
What are primary consumers?
they are in the second trophic level (herbivores)
consume organic molecules (biomass) of primary producers
Use energy consumed (Ein) to support its energy budget
Excess energy will be turned into new biomass (Egrowth)
Biomass production is called:
secondary production
What are secondary/tertiary consumers?
- in the 3/4th trophic level (carnivores/omnivores)
- organisms that consume the organic molecules (biomass) of both producers and consumers in a lower trophic level
- Use energy consumed (Ein) to support its energy budget
- Excess will be turned into new biomass (Egrowth)
What are decomposers/detritivores
consume the dead organic matter of primary producers, primary consumers. Etc.
Cycle nutrients back to earth
Secondary production
what is the equation for Ecological efficiency for one level?
net productivity of level we want/net productivity level below it
measured as percentage
Ecological efficiency is always approximately ____%
10
what are the forces that regulate trophic structure?
bottom up control
top down control
What is bottom up control?
resource abundance (eutrophication) regulates trophic structure
Energy in each trophic level is determined by the energy in the lower trophic level (bottom-up), if bottom levels are changed top level also changes
ex. if theres more phytoplankton. then there is more zooplankton
if there is more zooplankton, then there is more fish
What is top down control?
predation regulates trophic structure
Organisms in each trophic level are limited by predators in the next/higher trophic level
ex. removing big fish from lake causes minnows to grow more, since the predator is gone
What is a trophic cascade?
when adding/removing a top predator from an ecosystem results in an alternating (increase, decrease cascading) effect down the rest of the food web/chain.
ex. removing the big fish: minnows go up, zooplankton goes down, phytoplankton goes up
What is a keystone species?
species that is small in number but has a large effect on other organisms if removed from ecosystem (not a trophic cascade)
