Describe the carbon cycle

5.1.8 · Biology › Ecology & Ecosystems

Carbon cycle KYA hai?

Carbon stores (reservoirs) mein hold hoti hai aur fluxes (processes) se move karti hai:

Store	Carbon ki form
Atmosphere	carbon dioxide gas (CO₂), plus kuch methane (CH₄)
Living organisms	carbohydrates, fats, proteins
Oceans	dissolved CO₂, hydrogencarbonate (HCO₃⁻), carbonate (CO₃²⁻) ions, aur particulate organic carbon (plankton, detritus)
Fossil fuels	coal, oil, natural gas
Rocks	carbonate rock (jaise limestone, chalk = CaCO₃)

Carbon kaise move karti hai — biological fluxes

Ise living things mein IN aur living things se OUT ke roop mein socho.

Feeding carbon ko food chains ke saath transfer karti hai (plant → herbivore → carnivore) organic molecules ke roop mein.

Decomposition (aerobic): jab organisms oxygen ki presence mein marte hain, toh decomposers (bacteria & fungi) dead matter par feed karte hain aur respire karte hain, carbon ko CO₂ ke roop mein air mein wapas bhejte hain. Inke bina, carbon corpses mein trapped ho jaati.

Combustion (burning): wood ya fossil fuels jalane se stored carbon CO₂ ke roop mein release hoti hai: $fuel + O_{2} \to C O_{2} + H_{2} O$

Fossil fuel formation: agar dead matter decomposers ke pahunchne se pehle bury ho jaaye (anoxic), toh millions of years mein pressure aur heat ise coal, oil aur gas mein badal dete hain.

Carbon kaise move karti hai — ocean aur rock (geological) fluxes

Dual-coding: diagram padhna

Hawa mein UPAR arrows = CO₂/CH₄ release → respiration, combustion, decomposition, volcanoes, ocean outgassing.
Hawa se NEECHE arrows = removal → photosynthesis, ocean dissolution, rock weathering.
Sideways arrows = feeding/death (carbon organic rehti hai, sirf organism badal jaata hai).
Lamba slow loop = shells → sediment → rock → subduction → volcano.

Worked reasoning examples

Common mistakes (steel-manned)

Forecast-then-verify

Recall Reveal karne se pehle predict karo

Q: Agar atmospheric CO₂ achanak double ho jaaye, toh TWO natural processes batao jo excess remove karna shuru kar dein — aur batao kaunsi faster hai. Predict... Answer: (1) Ocean dissolution — zyada CO₂ seawater mein dissolve hoti hai (fast, years–decades). (2) Rock weathering — carbonic acid silicate rock weather karti hai (bahut slow, thousands+ years). Dissolution pehle kaam karta hai lekin iska limited capacity hai; weathering ultimate long-term sink hai.

Flashcards

Kaun sa process biologically atmosphere se CO₂ remove karta hai?

Photosynthesis

Photosynthesis ki word equation?

Carbon dioxide + water → glucose + oxygen (light use karke)

Kaun se processes CO₂ ko atmosphere mein wapas bhejte hain?

Respiration, aerobic decomposition, combustion, volcanic outgassing, ocean outgassing

Oxygen-free conditions mein decomposition se kaun si gas produce hoti hai?

Methane (CH₄), methanogenesis ke zariye

Aerobic decomposition kaun se organisms karte hain?

Bacteria aur fungi (decomposers)

Ocean mein carbon kin do main dissolved forms mein store hoti hai?

Hydrogencarbonate (HCO₃⁻) aur carbonate (CO₃²⁻) ions

Rock weathering atmospheric CO₂ par kya effect karti hai?

Yeh CO₂ remove karti hai (carbonic acid silicate/carbonate rock weather karti hai), ek long-term sink hai

Carbonate rock (limestone) kaise banti hai?

Marine organisms CaCO₃ shells precipitate karte hain jo sink ho jaate hain, accumulate aur compact ho jaate hain millions of years mein

Buried carbonate carbon hawa mein kaise wapas aata hai?

Subduction ise heat karta hai, CO₂ volcanoes/vents ke zariye release hoti hai

Fossil fuels kaise bante hain?

Dead organisms oxygen ke bina bury ho jaate hain, millions of years mein heat/pressure se compress hote hain

Kaun se do reservoirs mein sabse zyada carbon hoti hai?

Rocks (carbonate) aur oceans

Kaun si human activity extra CO₂ add kar ke cycle unbalance karti hai?

Fossil fuels ka combustion

Recall Feynman: ek 12-saal ke bachche ko samjhao

Socho carbon atoms chhote Lego bricks hain. Earth par inki ek fixed number hai. Plants hawa se bricks khinchti hain (photosynthesis) aur unhe food mein build karti hain. Animals woh food khaate hain aur bricks le lete hain. Jab bhi koi saanс chhodta hai, ya ek bug dead leaf ko sadhata hai, bricks wapas hawa mein float kar jaate hain — aur ek swamp mein jahan hawa nahi hai, bricks methane naam ki ek alag gas ke roop mein nikalti hain. Kuch bricks sea mein dissolve ho jaate hain; sea creatures unse shells banate hain, aur woh shells rock (jaise chalk) ban jaate hain jo bricks ko millions of years tak pakad ke rakhti hai — jab tak ek volcano finally unhe belch back out nahi karta. Toh wahi bricks baar baar reuse hoti hain, kuch fast, kuch super slow. Problem: jab hum coal aur oil khod ke jaalaate hain, toh loads of extra purani bricks ek saath hawa mein dump ho jaati hain, aur woh planet warm kar deti hain.

Connections

Photosynthesis — main biological CO₂ removal step
Respiration — reverse process, main CO₂ release
Decomposers and decay — carbon recycling; aerobic (CO₂) vs anaerobic (CH₄)
Food chains and energy flow — carbon organisms ke beech kaise move karti hai
Ocean acidification and carbonate chemistry — seawater CO₂/HCO₃⁻/CO₃²⁻ equilibrium
Rock cycle and weathering — geological carbon drawdown aur return
The greenhouse effect and climate change — cycle unbalance hone par kya hota hai
Fossil fuels — long-term carbon store
Nitrogen cycle — compare karne ke liye ek parallel nutrient cycle