1.Multiple sources contribute; CO2 is primary but not sole
cause
2.Excess nutrients cause eutrophication and dead zones
3.Nutrient cycling: Natural ecosystems like prairies recycle nutrients through nitrogen-fixing bacteria and decomposition, while agricultural monocultures deplete soil nutrients and require synthetic fertilizers that contribute to runoff and pollution.
REFSTUDY GUIDE: Big IdeasUse to answer form questions
1.Atmospheric N2 (78% of air) is unusable by plants.
Only specialized bacteria can "fix" it into usable forms.
2.Legumes host nitrogen-fixing bacteria in root nodules.
Prairie plants include legumes = self-fertilizing ecosystem.
DRAWKEY TERMSGoogle each → Images tab → sketch what you see
Nitrogen fixation
N2 -> usable N (bacteria only)
Legume
Plant with N-fixing root nodules
Denitrification
NO3 -> N2 gas return
Runoff
Excess N flowing to waterways
WRITEFOCUS QUESTIONYour initial thinking
Why does corn need fertilizer when native prairie grass stays green
without any?
Both corn and prairie plants need nitrogen to make proteins. Air is
78% N2 gas. Yet farmers spend billions on fertilizer for corn, while
prairie plants thrive with zero inputs. What's the difference?
I think the difference is...
WRITEAFTER HOOK FORMReflect before continuing
I learned that nitrogen...
Station 1 — Nitrogen Fixation
N-fixing bacteria convert...
Legumes help prairie plants because...
This explains the phenomenon because...
Station 1 — Nitrogen Fixation
CHECKPOINT:nitrogen fixation = N2 gas
-> NH3 (by bacteria only)
N-fixing bacteria convert...
Legumes help prairie plants because...
This explains the phenomenon because...
Station 2 — Fertilizer Data
The data shows that only ___% of fertilizer...
The rest goes to... because...
This connects to dead zones (W2) because...
CHECKDAY 1 CHECK-INBefore you leave
Q1:What do nitrogen-fixing bacteria do that plants cannot?
Q2:Where do nutrients causing Gulf dead zones (W2) come from?
Confidence:
Nitrogen Cycle & Agriculture (Day 2)ANSWER KEY
Name:
Station 2 — Fertilizer Data
The data shows that only ___% of fertilizer...
The rest goes to... because...
This connects to dead zones (W2) because...
Station 3 — Sustainable Agriculture
CHECKPOINT:trade-off = giving up one
benefit to gain another
Crop rotation with legumes reduces fertilizer need by...
Cover crops reduce runoff because...
A trade-off farmers face is... vs...
DRAWYOUR NITROGEN CYCLE MODELComplete before exit
Model the nitrogen cycle showing: (1) Where N2
starts, (2) How bacteria fix it, (3) How plants use it, (4) Where
excess goes. Use arrows for flow,
labels for each step.
TODO: author answer text
Include: N2 in atmosphere Bacteria (soil OR nodules) Legume with nodules Arrows showing flow Runoff path (W2!)
CHECKTEST YOUR THINKINGRate each: FALSE ← 1–2–3–4–5 → TRUE
1. All plants can take nitrogen directly from air.
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2. More fertilizer always means better crops.
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3. Nitrogen and carbon cycles are completely separate.
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4. We could feed everyone without synthetic fertilizer.
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5. Prairies are always better for the environment than farms.
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Defend TWO of your ratings - what do you know that you know?