Chapter 12 (Ecosystem)

the genius April 07, 2026

 

Ecosystem: Class 12 Biology Chapter 12 Complete Guide

Ecosystem ka matlab hai ek aisa functional unit jahan living organisms (plants, animals) apne physical environment (hawa, mitti, paani) ke saath interact karte hain. Ecosystem chhota bhi ho sakta hai (ek chhota talab) aur bahut bada bhi (ek jungle ya samundar).

1. Ecosystem ka Structure aur Function

Ek ecosystem ke char main pillars hote hain:

  1. Productivity: Khana banana (Photosynthesis).

  2. Decomposition: Mare hue organisms ko todna.

  3. Energy Flow: Ek se dusre tak energy ka jaana.

  4. Nutrient Cycling: Carbon aur Phosphorus jaise elements ka chakkar.

2. Productivity (Utpadakta)

  • Primary Production: Plants dwara banaya gaya biomass.

  • GPP (Gross Primary Productivity): Total khana jo plants ne banaya.

  • NPP (Net Primary Productivity): GPP mein se plants ne jo khud use kar liya (Respiration), uske baad jo bacha.

    • Formula: $NPP = GPP - R$

3. Decomposition (Apghatan)

Decomposition ko "Nature ka Garbage Disposal" kehte hain. Iske steps hain:

  1. Fragmentation: Detritivores (jaise kenchua/earthworm) kachre ko chhote tukdon mein todte hain.

  2. Leaching: Pani mein ghulne wale nutrients mitti ke neeche chale jate hain.

  3. Catabolism: Bacteria aur Fungi enzymes se complex cheezon ko simple banate hain.

  4. Humification: Ek dark substance "Humus" banta hai jo mitti ko upjau banata hai.

  5. Mineralisation: Humus se inorganic nutrients (jaise $N, P, K$) nikalna.

4. Energy Flow (Urja ka Bahav)

Suraj (Sun) energy ka main source hai. Energy hamesha unidirectional (ek hi taraf) behti hai.

  • 10% Law: Ek trophic level se dusre level tak sirf 10% energy hi pahunchti hai. Baaki 90% heat ke roop mein nikal jati hai.

  • Food Chain: Producer $\rightarrow$ Herbivore $\rightarrow$ Carnivore.

  • Food Web: Jab bahut saari food chains aapas mein judi hon.

5. Ecological Pyramids

Charles Elton ne ye concept diya tha, isliye ise "Eltonian Pyramids" bhi kehte hain:

  1. Pyramid of Number: Grassland mein seedha (Upright) hota hai.

  2. Pyramid of Biomass: Samundar (Sea) mein aksar Inverted (ulta) hota hai kyunki phytoplankton ka weight unhe khane wali machhliyon se kam hota hai.

  3. Pyramid of Energy: Yeh HAMESHA UPRIGHT hota hai kyunki energy har level par kam hoti jati hai.

6. Ecological Succession

Khaali jagah par dhire-dhire naye organisms ka aana aur ek stable community banana Succession kehlata hai.

  • Primary Succession: Jahan pehle kabhi life nahi thi (jaise naya volcano ya rock). Ismein bahut waqt lagta hai.

  • Secondary Succession: Jahan pehle life thi par kisi wajah se khatam ho gayi (jaise baadh ya aag). Yeh fast hota hai.

  • Pioneer Species: Jo sabse pehle aate hain (e.g., Lichens on rocks).

  • Climax Community: Jo sabse last aur stable hoti hai (e.g., Forest).

7. Nutrient Cycling (Biogeochemical Cycles)

Nutrients kabhi khatam nahi hote, wo recycle hote hain:

  • Gaseous Cycle: Carbon aur Nitrogen cycle (Atmosphere se).

  • Sedimentary Cycle: Phosphorus aur Sulphur cycle (Rocks aur mitti se).

    • Shutterstock

Conclusion

Chapter 12 Ecosystem se Pyramids aur Decomposition ke steps par aksar long questions aate hain. NEET ke liye 10% law aur Inverted pyramids ke examples yaad rakhein.

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