Chapter 13 (Biodiversity and Conservation)

the genius April 07, 2026

 

Biodiversity and Conservation: Class 12 Biology Chapter 13 Full Guide

Biodiversity ka matlab hai "Life ki Variety". Edward Wilson ne is term ko popular kiya tha. Yeh variety sirf janwaron mein nahi, balki genes, species aur pure ecosystem mein hoti hai.

1. Levels of Biodiversity (Biodiversity ke Star)

Biodiversity ko teen main levels mein baanta gaya hai:

  1. Genetic Diversity: Ek hi species ke andar genes ka badlav (e.g., India mein aam (Mango) ki 1000 se zyada varieties hain).

  2. Species Diversity: Alag-alag species ki sankhya (e.g., Western Ghats mein amphibians ki variety Eastern Ghats se zyada hai).

  3. Ecological Diversity: Ecosystems ki variety (e.g., India mein deserts, rainforests aur mangroves ka hona).

2. How Many Species are there on Earth?

  • IUCN (2004): Ke hisaab se total 1.5 million se zyada species record ki gayi hain.

  • Robert May's Estimate: Unhone bataya ki dharti par lagbhag 7 million species ho sakti hain, jisme se bahut si abhi khojni baaki hain.

  • India ki Richness: India duniya ke 2.4% land area par hai, lekin yahan world ki 8.1% biodiversity payi jati hai. Isliye India ek "Mega-diversity" country hai.

3. Patterns of Biodiversity

Biodiversity har jagah barabar nahi hoti:

  • Latitudinal Gradients: Jab hum equator (bhoomadhya rekha) se poles (dhruvon) ki taraf jate hain, toh biodiversity kam hoti jati hai. Amazon Rainforest (South America) mein duniya ki sabse zyada biodiversity hai.

  • Species-Area Relationship: Alexander von Humboldt ne bataya ki jaise-jaise hum area badhate hain, species ki ginti badhti hai, lekin ek limit tak.

    • Formula: $\log S = \log C + Z \log A$

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4. Loss of Biodiversity: The Evil Quartet

Species ke khatam hone ke chaar main kaaran hain, jinhe "The Evil Quartet" kehte hain:

  1. Habitat Loss and Fragmentation: Jungalon ko katna (e.g., Tropical rainforests ka 14% se ghatkar 6% reh jana).

  2. Over-exploitation: Zarurat se zyada istemal (e.g., Steller’s sea cow aur Passenger pigeon ka khatam hona).

  3. Alien Species Invasions: Bahari species ka aana (e.g., Water Hyacinth aur Nile Perch).

  4. Co-extinctions: Jab ek species khatam hoti hai, toh uspar nirbhar dusri species bhi khatam ho jati hai.

5. Biodiversity Conservation (Bachav ke Tarike)

Humein biodiversity ko kyun bachana chahiye? Iske teen karan hain: Narrowly utilitarian (khana, dawa), Broadly utilitarian (oxygen, pollination), aur Ethical (moral zimmedari).

Conservation ke do main tarike hain:

  1. In-situ Conservation (On-site): Organisms ko unke natural ghar mein bachana.

    • Biodiversity Hotspots: Duniya mein 34 hotspots hain (e.g., Western Ghats, Himalayas).

    • Protected Areas: National Parks (90), Wildlife Sanctuaries (448), aur Biosphere Reserves (14).

    • Sacred Groves: Dharmik astha ki wajah se bachaye gaye jungle (e.g., Khasi and Jaintia Hills in Meghalaya).

  2. Ex-situ Conservation (Off-site): Organisms ko unke ghar se nikaal kar special jagah rakhna.

    • Examples: Zoological Parks (Zoo), Botanical Gardens, Wildlife Safari Parks.

    • Advanced methods: Seed banks, Cryopreservation ($-196^\circ C$ par tissue rakhna), aur In-vitro fertilization.

6. International Efforts

  • The Earth Summit (1992): Rio de Janeiro mein biodiversity bachane ka wada kiya gaya.

  • The World Summit (2002): Johannesburg mein 190 deshon ne 2010 tak biodiversity loss kam karne ka sankalp liya.

Conclusion

Chapter 13 se In-situ vs Ex-situ aur Evil Quartet par hamesha sawal aate hain. Biodiversity sirf padhne ke liye nahi, balki hamare bhavishya ke liye zaroori hai.

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