Topic 12: Ecosystem Energetics Flashcards
Ecosystem
community of organisms interacting with their environment under influences of environmental factors
Ecosystem energetics
study of how energy is fixed by autotrophs and made available to heterotrophs
autotrophs
producer - organisms that form nutrional organic substances (ie CO2)
heterotrophs
consumers - organisms able to derive nutritional requirements from complex organic substances
energy is measured as
Biomass
biomass
dry weight of organic matter
Primary producers
- 1st trophic level
- autotrophs that fix inorganic nutrients into organic molecules
- carry out primary production
Primary productivity
rate at which energy is fixed
Net primary production
what producer makes - what producer uses
- tells us how much energy is left for other trophic levels
Gross primary production
total amount of energy fixed into organic molecules in an ecosystem
5 things that affect primary production
light, temperature, precipitation, nitrogen and phosphorous concentrations
Light
know graph and 2 important points on it
- start of plateau = more light than enzyme can handle
- end of plateau & decrease because UV damange and radiation due to too much light decreases PP
Precipitation
temperature
pp increases as temperature increases bc enzyme reactions increase with temperatrue
nitrogen
deficiency is more in terrestrial as N is soluble in water
- limiting factor in terrestrial
phosphorous
limiting factor in aquatic as it is insoluble
increasing a limiting factor will cause a ___________ impact
greater
Primary consumers
2nd trophic level
- energy consumed (Ein) to support its energy budget
- herbivores
- biomass production is called secondary production
Secondary/Tertiary Consumers
3rd/4th trophic levels
- omnivores/carnivores
- energy consumed (E in) is used to support energy budget
- biomass production is called secondary production
Decomposers/detritivores
- cycle nutrients
- do secondary production
nutrients are always ______
cycled
energy always ________ in ___________, and is lost as _______
flows; one direction; heat
Ecological Efficiency
transfer of energy from one trophic level to another
- usually around 10%
EE=
(net primary productivity of higher TL)/(net primary productivity of lower TL) x 100%
Assimilation
amount of energy taken up
Keystone Species
critically important in maintenance of trophic structure; usually small in number
Forces that regulate trophic structure: (3)
bottom-up control, top-down control, trophic cascade
Bottom-up control
resource abundance regulates trophic structure - how energy in lower levels determines energy in higher levels
Top-down control
predation regulates trophic structure
Trophic cascade
changing a top predator often results in a cascading/alternating effect down the food chain
nutrients
elements required by organisms; cycled; in reservoirs
biochemical cycles
pathways describing how nutrients move between biotic and abiotic components
short term reservoirs hold nutrients for ___ 200 yrs
less than
long term reservoirs hold nutrients for ___ 200 yrs
more than
3 major nutrient reservoirs
terrestrial, aquatic, atmospheric
3 states of nutrients:
gas, soluble, insoluble
Generalized compartment model
available organic
available inorganic
unavailable organic
unavailable inorganic
Carbon cycle
carbon makes up 5% of dry mass; most abundant nutrient; unit of energy currency; glucose (carbon chain) essential for energy transfer; cycles through all 4 nutrient compartments
Short-term carbon cycle
carbon increases (CO2) in winter because humans burn for heat; carbon decreases in summer as more plants use it
Long-term carbon cycle
carbon content (CO2) has increased due to human activity
Carbon isotopes
C^12 = 99% - most organisms and P/S prefer this; fossil fuels are mostly made up of C^12
Green House Effect
result of change of gases in atmospheric section; earth radiates energy absorbed from sun back to space
Greenhouse gases increase
prevents earth from radiating energy back into space
Anthropogenic CO2 absorbed by the ocean reacts with ___ to form __________, which turns into ____________ and ______ the pH
H2O; carbonic acid; bicarbonate; lowers
