Nitrogen Cycle Tournament
Eight H2 ecology rounds: who actually fixes N2, what flooding does to nitrate, the full cycle order, process matching, 78% atmospheric N2, eutrophication and N2O.
Biological nitrogen fixation is the reduction of atmospheric N2 to ammonia by nitrogenase, typically in bacteria such as Rhizobium in root nodules.
What this tournament tests
Each task maps to a distinct GCE A-Level cognitive demand. 8 timed rounds test the high-yield mechanism, regulation, sequence and quantitative reasoning that consistently appear on test day.
Fill in the Blank
Who fixes N2.
Disruptor
Flooded soil and denitrification.
Sequence Ordering
Atmosphere to atmosphere.
Match the Pairs
Five named conversions.
Numeric Input
Percent N2 in air.
Select All That Apply
Rhizobium, nitrifiers, Haber-Bosch.
Odd One Out
Denitrification removes available N.
Eutrophication Disruptor
Algal blooms and N2O.
Public leaderboard
Your score posts to a global, persistent leaderboard scored by points first, time as tiebreaker.
Nitrogen cycle in 60 seconds
Fixation N2 → NH3. Nitrification NH4+ → NO3- (needs O2). Assimilation into amino acids.
Ammonification returns organic N to ammonium. Denitrification returns nitrate to N2 when oxygen is gone.
Humans add Haber-Bosch N. The leak is nitrate to water (eutrophication) and N2O to air.
Flooded, anoxic soil flips the cycle: nitrification (needs O2) stalls and denitrifiers convert nitrate back to N2. That is why paddy fields lose fertiliser nitrogen as gas, and why the same pathway is a 9744 human-impact item.
FAQ
Who actually fixes atmospheric N2?
Diazotrophs — free-living bacteria such as Azotobacter and symbiotic Rhizobium in root nodules. Lightning and the Haber-Bosch process also reduce N2, but plants and animals cannot fix N2 themselves. They assimilate ammonium or nitrate.
Why does flooding increase denitrification?
Nitrifiers need oxygen to oxidise ammonium to nitrate. Waterlogged soil goes anoxic, so denitrifying bacteria use nitrate as an electron acceptor and release N2 (and some N2O). Available nitrogen leaves the field as gas.
Is this the same as the MCAT amino-acid catabolism game?
No. That MCAT page is intracellular amino-acid breakdown. This tournament is the ecosystem nitrogen cycle — fixation through denitrification — written for H2 Biology 9744 ecology.
Do I need an account?
No. Play in the browser. Scores go to a public leaderboard under a generated name.