carbon and nitrogen cycles exam 2

what is a carbon stock

a reservior where carbon is stored (atmosphere, ocean, soil)

what is a carbon flux

the movement of carbon between different stocks (photosynthesis, respiration, combustion)

roles of bacteria in the nitrogen cycle

nitrogen fixation, nitrification, denitrification

fixation

turning an inorganic form into an organic form; bonding

nitrogen cycle is a series of reactions where either _____ or ______ is _____ or _______ from nitrogen

hydrogen, oxygen, added, removed

what drives the carbon and nitrogen cycles?

living organisms (esp prokaryotes)

fixation

inorganic to organic/useable form

what enzyme fixes carbon

rubisco

how are autotrophy and heterotrophy related?

opposites that form the carbon cycle loop

what do autotrophs do?

fix carbon into organic molecules

what do heterotrophs do?

break down organic molecules and release carbon

what percent of photosynthesis occurs in the ocean

50%

what organisms dominate ocean photosynthesis

cyanobacteria, phytoplankton

what is the microbial loop

autotrophs fix carbon and heterotrophs respire it back

how does carbon escape the microbial loop

biological carbon pump (sinking organic matter to seafloor)

what happens to buried carbon long-term?

becomes fossil fuels

where is the most carbon stored long term

rocks

why is carbon increasing today

humans are adding carbon faster than it is being removed

why are prokaryotes essential for the nitrogen cycle

only they can convert n2 into useable forms

how does carbon enter ecosystems

photosynthesis (co2→ organic carbon)

how does carbon move through organisms

biological carbon cycle (produces, consumers, decomposers)

how does carbon return to the atmosphere

cellular respiration, decomposition, burning

what balances the carbon cycle on short term scales

autotrophy vs heterotrophy

what evidence shows rising co2 levels

keeling curve

one major consequence of rising carbon levels

ocean acidification

where is most nitrogen found on earth

atmosphere as N2

how does nitrogen enter ecosystems?

nitrogen fixation (N2→ NH3)

what are the main steps of the nitrogen cycle

fixation, nitrification, denitrification, mineralization

how does nitrogen move through organisms

plants absorb fixed inorganic nitrogen, animals eat plants, decomposition returns N to soil

how does nitrogen return to the atmosphere

denitrification →N2

what forms of nitrogen can plants use

ammonium (NH₄⁺) and nitrate (NO₃^-)

what forms of nitrogen can plants not use

N₂ and NO₂^-