Organisms and Populations: Class 12 Biology Chapter 11 Study Guide
Ecology wo science hai jo organisms aur unke physical (abiotic) environment ke beech ke rishte ko samajhati hai. Is chapter mein hum "Individual" se lekar poori "Population" tak ki baate karenge.
1. Organism aur Uska Environment
Har organism ek specific jagah rehna pasand karta hai jise uska Habitat kehte hain. Environment mein do tarah ke factors hote hain:
Abiotic Factors: Temperature, Water, Light, aur Soil. (Temperature sabse important factor hai).
Biotic Factors: Pathogens, Parasites, Predators, aur Competitors.
Organisms Kaise Respond Karte Hain?
Jab bahar ka mahol badalta hai, toh organisms ye char raste apnate hain:
Regulate: Apni body ka internal environment constant rakhna (e.g., Humans ka $37^\circ C$ temperature).
Conform: Jo apni body ko maintain nahi kar paate aur bahar ke hisaab se badal jate hain (99% animals aur plants).
Migrate: Kharab waqt mein kahin aur chale jana (e.g., Keoladeo National Park mein aane wale Siberian birds).
Suspend: Apni activity rok dena (e.g., Bacteria mein Spores, Bhalu mein Hibernation/Winter sleep, aur Machhliyon mein Aestivation/Summer sleep).
2. Adaptations (Anukoolan)
Survival ke liye organisms apne andar kuch badlav laate hain:
Desert Plants (e.g., Opuntia): Inmein leaves kaante (spines) ban jati hain aur stem photosynthesis karta hai (CAM pathway).
Allen’s Rule: Thande ilaqon ke mammals ke kaan aur hath-pair chhote hote hain taaki heat loss kam ho.
Altitude Sickness: Jab hum pahadon par jate hain, toh body RBC production badha deti hai taaki oxygen ki kami puri ho sake.
3. Population Attributes
Ek population sirf numbers nahi, balki usmein kuch aur khoobiyan bhi hoti hain:
Birth Rate aur Death Rate: Per capita (prati vyakti) ke hisaab se calculate kiya jata hai.
Sex Ratio: Male aur Female ka anupaat.
Age Pyramids: Isse pata chalta hai ki population badh rahi hai (Expanding), barabar hai (Stable), ya ghat rahi hai (Declining).
4. Population Growth Models
Population kaise badhti hai, iske do main models hain:
Exponential Growth: Jab resources (khana-paani) unlimited hon. Iska graph J-shaped hota hai.
Logistic Growth: Jab resources limited hon. Ismein ek Carrying Capacity (K) hoti hai jiske upar population nahi ja sakti. Iska graph S-shaped (Sigmoid) hota hai. (Yeh zyada realistic hai).
5. Population Interactions (Aapsi Rishte)
Do alag species jab saath rehti hain, toh unke beech alag tarah ke rishte bante hain:
| Interaction Name | Species A | Species B | Example |
| Mutualism | + | + | Lichens (Algae + Fungi) |
| Competition | - | - | Abingdon Tortoise vs Goats |
| Predation | + | - | Sher aur Hiran |
| Parasitism | + | - | Cuscuta (Amarbel) on plants |
| Commensalism | + | 0 | Orchid on Mango tree |
| Amensalism | - | 0 | Penicillium killing Bacteria |
(Note: + ka matlab fayda, - ka nuksan, aur 0 ka matlab koi asar nahi.)
Conclusion
Chapter 11 Ecology ka base hai. Population Interactions aur Growth Curves se har saal Boards aur NEET mein sawal pakka aate hain. Table 11.1 (Interactions) ko dhyan se ratt lein!
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