Biodiversity and Conservation

NCERT Line-by-Line Breakdown for NEET 2026

Unit 5: Ecology and Environment

Biodiversity refers to the combined diversity at all levels of biological organization. The term was popularized by the sociobiologist Edward Wilson. It is not uniform throughout the world but shows uneven distribution.

1. Levels of Biodiversity

1. Genetic Diversity
Variation within a species.
Example: Medicinal plant Rauwolfia vomitoria (Himalayas) shows variation in potency of Reserpine. India has >50,000 strains of Rice and 1,000 varieties of Mango.

2. Species Diversity
Diversity at the species level.
Example: Western Ghats have greater amphibian species diversity than Eastern Ghats.

3. Ecological Diversity
Diversity at ecosystem level.
Example: India (Deserts, Rain forests, Mangroves, Coral reefs) has greater ecosystem diversity than a Scandinavian country like Norway.

Global Species Count: According to IUCN (2004), slightly more than 1.5 million. Robert May estimates global species diversity at about 7 million.

2. Patterns of Biodiversity

A. Latitudinal Gradients

Diversity decreases as we move away from the Equator towards Poles.

Amazon Rain Forest (South America): Greatest biodiversity on Earth. (40,000 plants, 3,000 fishes, 1,300 birds).
Why Tropics? (1) Undisturbed for millions of years (evolutionary time), (2) Less seasonal/More constant environment, (3) More solar energy (higher productivity).

B. Species-Area Relationship

Proposed by German naturalist Alexander von Humboldt.

“Within a region, species richness increases with increasing explored area, but only up to a limit.”
Equation: log S = log C + Z log A
(S=Species richness, A=Area, C=Y-intercept, Z=Slope of line).

Value of Z (Regression coefficient):
• Generally 0.1 to 0.2.
• For large continents: 0.6 to 1.2.
• Frugivorous birds/mammals in tropical forests: 1.15.

3. Importance and Loss of Biodiversity

Why does it matter?

David Tilman’s plots: Plots with more species showed less year-to-year variation in total biomass (Stability).
Rivet Popper Hypothesis (Paul Ehrlich): Airplane = Ecosystem; Rivets = Species. Removing rivets (extinction) weakens the plane. Removing a key rivet (Keystone species) on wings causes serious threat.

Loss of Biodiversity

IUCN Red List (2004) documents extinction of 784 species in last 500 years. Examples: Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Steller’s Sea Cow (Russia).

💀 The Evil Quartet (Causes of Loss):

Habitat Loss & Fragmentation: Most important cause. (Amazon forest cut for soya beans/cattle).
Over-exploitation: Humans turning ‘need’ into ‘greed’. (Passenger pigeon, Steller’s sea cow).
Alien Species Invasions: Nile Perch introduced in Lake Victoria killed 200 species of Cichlid fish. Water Hyacinth (Terror of Bengal). African Catfish (Clarias gariepinus).
Co-extinction: When a host becomes extinct, its unique parasites also die.

4. Conservation Strategies

Why Conserve?

Narrowly Utilitarian: Economic benefits (Food, firewood, fiber, medicines like Vinblastine/Curcumin).
Broadly Utilitarian: Ecosystem services (Oxygen, Pollination, Flood control).
Ethical: Moral duty to care for every living creature.

How to Conserve?

In-situ (On site)	Ex-situ (Off site)
Protecting the whole ecosystem.	Threatened animals/plants taken out from natural habitat to special setting.
• Biodiversity Hotspots: High endemism & high threat. (Western Ghats & Sri Lanka, Indo-Burma, Himalaya). • Biosphere Reserves: 14 in India. • National Parks (90) & Sanctuaries (448). • Sacred Groves: Khasi & Jaintia Hills (Meghalaya), Aravalli (Rajasthan).	• Zoological Parks. • Botanical Gardens. • Wildlife Safari Parks. • Cryopreservation: Gametes preserved at -196°C (Liquid N₂). • Seed Banks.

International Efforts

The Earth Summit (Rio, 1992): Convention on Biological Diversity (CBD).
World Summit (Johannesburg, 2002): 190 countries pledged to reduce the rate of biodiversity loss by 2010.

📝 Rapid Fire MCQs

Q1. Which of the following is an example of ex-situ conservation?

A) Sacred Grove
B) National Park
C) Seed Bank
D) Biosphere Reserve

Click to check Answer

Answer: C) Seed Bank (Off-site conservation).

Q2. In the species-area relationship equation log S = log C + Z log A, ‘Z’ represents:

A) Species richness
B) Slope of the line (Regression coefficient)
C) Y-intercept
D) Area