Biodiversity and Conservation: NEET Biology Notes | NCERT Class 12 Chapter 13

*NEET 2027: Chapter 13 Biodiversity and Conservation - Detailed Short Notes* 🌍  

_Class 12 Biology | NCERT Line-by-Line + PYQ  4Q Tak Aa Sakte Hain_  

### *1. Biodiversity - Concept & Levels*  

- *Term*: Edward Wilson = Father of Biodiversity. Coined 'biodiversity'.  

- *Definition*: Combined diversity at all levels of biological organization.  

- *3 Levels with NEET Examples*:

**Level** **Meaning** **NEET Example**

**Genetic Diversity** Diversity within species due to genes 1. 50,000 rice varieties in India  2. 1,000 mango varieties  3. Rauwolfia vomitoria = Reserpine variation

**Species Diversity** Diversity at species level Western Ghats amphibians > Eastern Ghats

**Ecological Diversity** Diversity at ecosystem level India: Deserts, Rainforests, Mangroves, Coral reefs, Alpine meadows

### *2. Magnitude of Biodiversity*  

- *Described Species*: 1.7-1.8 million. Robert May estimate: Global = 7 million species.  

- *Proportion*: Animals = 70%. Plants = 22%. Fungi = More than all vertebrates combined.  

- *India’s Share*: 2.4% world land area but 8.1% global species. 12 megadiverse countries.  

- *NEET Trap*: Insects = most species rich group = 70% of total animals. Fungi > Algae + Ferns + Mosses + Lichens.  

### *3. Patterns of Biodiversity*  

*A. Latitudinal Gradients*  

1. *Rule*: Species richness ↓ as we move from equator to poles.  

2. *Data*: Birds: Colombia = 1,400, New York = 105, Greenland = 56, India = 1,200.  

3. *Why Tropics Have More?* `NEET Fav 3 Points`  

      - *Time*: Tropics undisturbed for millions of years. Temperate had glaciations.  

      - *Solar Energy*: More sunlight → More productivity → More species.  

      - *Less Seasonal*: Constant environment → Niche specialization promoted.  

*B. Species-Area Relationship*  

- *Given by*: Alexander von Humboldt in South American jungles.  

- *Graph*: Rectangular hyperbola. On log scale = Straight line.

\log S = \log C + Z \log A

  

  S = Species richness, Z = Regression coefficient = Slope, C = Y-intercept.  

- *Z Value*:  

    1. *Normal*: 0.1 to 0.2 for plants in Britain, birds in California.  

    2. *Continents*: 0.6 to 1.2. Frugivorous birds & mammals in tropical forests. Steeper slope = more species per unit area.  

### *4. Importance of Species Diversity to Ecosystem*  

- *David Tilman*: Plots with more species show less year-to-year variation in biomass. ↑ Diversity = ↑ Productivity.  

- *Rivet Popper Hypothesis*: Paul Ehrlich.  

  Airplane = Ecosystem. Rivets = Species.  

    1. *Popping few rivets* = Loss of non-critical species = Plane still flies = Minor effect.  

    2. *Popping key rivets* = Loss of keystone species = Plane crashes = Ecosystem collapse.  

*Stable Community Features*:  

1. No too much variation in productivity year to year.  

2. Resistant to occasional natural/man-made disturbances.  

3. Resistant to alien species invasion.  

### *5. Loss of Biodiversity*  

- *Current Episode*: 6th Mass Extinction. Anthropogenic. 100-1000 times faster.  

- *IUCN Red List 2004*: 784 extinctions. Last 20 years = 27 species extinct.  

- *Recent Extinctions*:  

    1. *Dodo* = Mauritius. 2. *Quagga* = Africa. 3. *Thylacine* = Australia. 4. *Steller’s Sea Cow* = Russia.  

    5. *3 Subspecies of Tiger*: Bali, Javan, Caspian.  

*The Evil Quartet* `Har Saal 1Q Pakka`

**Cause** **Mechanism** **NEET Example** **Data**

**1. Habitat Loss & Fragmentation** Biggest cause. Forests cut for agriculture, urbanization Amazon rainforest = 14% to 6%. 'Lungs of planet' being cut Tropical rainforest once 14% Earth → Now 6%

**2. Over-exploitation** Humans exploit beyond regeneration capacity Steller’s sea cow, Passenger pigeon extinct due to overhunting Marine fish stocks overharvested

**3. Alien Species Invasion** Non-native species outcompete native 1. Nile perch → 200 cichlid fish extinct in Lake Victoria  2. Parthenium = Carrot grass  3. Lantana  4. Eicchornia = Water hyacinth = Terror of Bengal Clarias gariepinus = African catfish threat to Indian catfish

**4. Co-extinctions** When species becomes extinct, obligate associate also extinct Plant-pollinator mutualism. If host fish extinct, unique parasite extinct Fig & Wasp. Fig extinct → Wasp extinct

### *6. Why Should We Conserve?*  

1. *Narrowly Utilitarian*: Direct economic benefit.  

      - Food: Cereals, Pulses, Fruits. Firewood, Fiber, Construction material.  

      - Industrial: Tannins, Lubricants, Dyes, Resins, Perfumes.  

      - *Drugs*: 25% drugs from plants. 25,000 species used by tribals.  

2. *Broadly Utilitarian*: Ecosystem services.  

      - *Amazon*: 20% of total O₂ in Earth atmosphere via photosynthesis.  

      - *Pollination*: Bees, birds, bats. Climate regulation. Flood control.  

3. *Ethical Argument*: Millions of plants, animals, microbes share planet. We must realize every species has intrinsic value. Moral duty to pass biodiversity to future generations.  

### *7. How Do We Conserve?*  

*A. In-situ Conservation* `On-site = In natural habitat`

**Type** **Features** **Example** **NEET Point**

**Biosphere Reserve** 3 zones: Core = No activity, Buffer = Limited, Transition = Settlement 14 in India. Nilgiri, Nanda Devi, Sundarbans UNESCO MAB Programme

**National Park** Strict reserve. No human activity 90 in India. Jim Corbett = 1st, Kanha, Kaziranga Kaziranga = One-horned Rhino

**Wildlife Sanctuary** Limited human activity allowed 448 in India. Periyar, Manas Project Tiger in some

**Sacred Groves** Religious protection to forest patches Khasi & Jaintia Hills = Meghalaya, Aravalli = Rajasthan, Western Ghats = Maharashtra, Karnataka Last refuge for rare plants

*Hotspots*: Norman Myers concept.  

- *Criteria*: 1. High species richness 2. High endemism 3. Most threatened.  

- *Global*: 34 hotspots. Cover <2% Earth but have 44% plants & 35% vertebrates.  

- *India*: 3 Hotspots = 1. Western Ghats & Sri Lanka  2. Indo-Burma  3. Himalaya.  

*B. Ex-situ Conservation* `Off-site = Outside natural habitat`  

1. *Zoological Parks*: Captive breeding of threatened animals. Genetic diversity ↓ but extinction avoided.  

2. *Botanical Gardens*: Plant collection for conservation.  

3. *Cryopreservation*: Gametes of threatened species preserved at -196°C in liquid N₂.  

4. *Seed Banks*: Seeds of different genetic strains preserved for long periods.  

5. *Tissue Culture*: Micropropagation of threatened plants.  

*NEET Gold*: In-situ = Cheaper, maintain wild population. Ex-situ = Expensive, last resort when species near extinction.  

### *8. International Efforts & Indian Laws*  

1. *Earth Summit*: Rio de Janeiro, Brazil 1992. Convention on Biological Diversity = CBD.  

2. *World Summit*: Johannesburg, South Africa 2002. 190 countries pledged significant reduction in biodiversity loss by 2010.  

3. *Indian Laws*: Wildlife Protection Act 1972, Forest Conservation Act 1980.  

### *9. PYQ Hotspots 2019-2025* `Ratta Maar Lo`  

1. *Amazon rainforest O₂* = 20% via photosynthesis = NEET 2023, 2019.  

2. *Z value continents* = 0.6 to 1.2 = NEET 2022, 2017.  

3. *Khasi & Jaintia Hills sacred groves* = Meghalaya = NEET 2021.  

4. *Evil Quartet* = Must memorize all 4 with examples = NEET 2020, 2024.  

5. *In-situ vs Ex-situ* = Diff + Examples = Asked 6 times in last 10 years.  

6. *Rivet popper hypothesis* = Paul Ehrlich = NEET 2020.  

7. *Hotspots in India* = 3 names = Western Ghats, Indo-Burma, Himalaya = NEET 2018.  

8. *Nile Perch example* = Alien species invasion = NEET 2024.  

9. *Genetic diversity example* = Rauwolfia, Rice, Mango = NEET 2016.  

10. *Biodiversity %*: Insects = 70% of animals. India = 8.1% global diversity.