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)
What are biogeochemical cycles?
Pathways that describe how nutrients move between biotic and abiotic components of an ecosystem
For nutrients, earth is a _______ system
closed
For energy, earth is a _______ system
open
Organisms need ________
nutrients
nutrients are _______
reservoirs
short term reservoirs are _____ years
<200
long term reservoirs are _____ years
> 200
biotic reservoirs are ______
organic molecules
abiotic reservoirs are ______
inorganic molecules
What are the three major geological nutrient reservoirs?
Terrestrial (land)
Aquatic (water)
Atmospheric (air)
What are the phases that nutrients exist in?
Gases (CO2)
Soluble (C,N,O)
Insoluble (P,K, Fe)
Short term reservoirs in the generalized compartment model are _______
available organic
available inorganic
Long term reservoirs in the generalized compartment model are _______
available inorganic
unavailable inorganic
available organic substances are:
animals
autotrophs (plants)
autotrophic bacteria, fungi
detritus
available inorganic substances are:
atmosphere
soil
water
sediments
unavailable organic substances are:
coal
oil
peat
unavailable inorganic substances are:
rocks and minerals
Carbon is about ____% dry mass
50
What is carbon?
the unit of energy currency in organisms and ecosystems (glucose transfers energy as carbon bond molecules)
What is the short term carbon cycle?
when carbon increases in winter and decreases in summer (fluctuates in short term)
but has an overall increase long term
What is the long term carbon cycle?
CO2 levels in the past (measured from air bubbles trapped in ice) indicate that the increase in carbon now is recent
CO2 has increased ___ percent in the last ____ years
30
50
How do humans cause an increase in carbon?
fossil fuel emissions
Types (isotopes) of carbon:
C12: 99% abundance
C13: 1% abundance
What type of carbon do most organisms contain, and photosynthesis prefer?
C12
What are fossil fuels and what happens when they’re burned?
they are remains of living organisms
when burned, release C12
this dilutes the atmospheric C13:C12 ratio
we can find the extra CO2 by looking at the changing ratio of C13:C12
As CO2 increases what happens to C13?
C13 decrease because more C12 is being produced
What are the main causes of CO2 production in Canada?
Oil and gas
What cause of CO2 stays low and constant in Canada?
cement
biggest source of CO2 production in the world is:
land use change (deforestation)
What is the greenhouse effect?
the earth (eventually) radiates the energy absorbed from the sun back into space
Without green house gasses (earth is -20 degrees)
With green house gasses (earth is 15 degrees, bc more heat is trapped in atmosphere)
What are the important green house gasses?
CH4, CO2, N2O, SF6
CH4 and N2O occur in much lower concentrations, so each molecule exerts a greater force
Which greenhouse gases causes the majority of change/effect?
CO2 and N2O
Increases in green house gasses are due to:
the exponential increase in human populations and industrialization
If we continue burning fossil fuels we could reach carbon concentration of ___:
840 ppm
What happens to the carbon after it is increased and sent into the atmosphere?
half of it stays in the atmosphere
fossil fuel carbon and land use change ends up in land and ocean sinks
the CO2 promotes plant growth
What happens to the carbon that is absorbed by the oceans?
carbon react with water to make carbonic acid, this acid lowers the ph of the ocean which make the ocean more acidic.
the carbonic acid eventually dissociates and releases H and bicarbonate
the H reacts with naturally occurring carbonate to make more bicarbonate
CO2 + H2O -> H2CO3 -> H+ + HCO3- ← 2H + + CO32-
Why do shell forming marine organisms need carbonate?
to form their calcium carbonate shells/skeletons
decrease in carbonate due to CO2 in ocean, causes them to form shells slower.
leaves them vulnerable to predation and infection
By what year will acidification will start
dissolving calcium carbonate shells?
2050
increases in methane can be due to:
permafrost melting: CH4 from the soil under the ice could arise
amazon rainforest: source of carbon sink and land use change
Boreal forest: fires release smoke and CH4
What is the tragedy of the commons?
Benefit to the individual outweighs
the cost to the collective
