Biodiversity and Conservation covers the three levels of biodiversity, patterns such as the latitudinal gradient and the species-area relationship, the importance of biodiversity and the causes of its loss (the Evil Quartet), the link between diversity and ecosystem stability, and in-situ and ex-situ conservation methods. It is a scoring NEET chapter where questions test named hypotheses, hotspot numbers, the Evil Quartet, and conservation terms and figures.
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What is Biodiversity
Biodiversity is the variety and variability of life, organised at three nested levels.
Term popularised by Edward Wilson
- Genetic: variation in genes within ONE species (e.g. reserpine in Rauwolfia)
- Species: variety of species in a region (Western Ghats > Eastern Ghats amphibians)
- Ecological: variety of habitats/ecosystems (India’s deserts, reefs, mangroves)
How Many Species
Most species are still undiscovered, and animals dominate the records.
IUCN 2004 figures
- Animals >70% of recorded species; insects are the largest animal group (~70%)
- Plants (algae+fungi+bryo+gymno+angio) only ~22%
- India: 2.4% of land area but 8.1% of global species → megadiverse
Latitudinal Gradient
Species diversity falls as you move from the equator to the poles.
Amazon = most biodiverse place on Earth
- Tropics undisturbed for millions of years → long evolutionary time
- Less seasonal, constant climate → niche specialisation
- More solar energy → higher productivity → more diversity
Species–Area Relationship
Within a region species richness rises with area but levels off (rectangular hyperbola).
Described by Alexander von Humboldt; straight line only on log–log axes
- S = species richness, A = area, C = intercept, Z = slope
- Z ≈ 0.1–0.2 for small areas (within a continent)
- Z ≈ 0.6–1.2 for very large areas (across continents) — steeper
Importance of Biodiversity
Reasons to conserve are grouped as narrowly utilitarian, broadly utilitarian and ethical.
~25% of drugs from plants; Amazon gives ~20% of atmospheric O2
- Narrowly utilitarian: direct products — food, fibre, firewood, medicines
- Broadly utilitarian: ecosystem services — O2, pollination, climate regulation
- Ethical: every species has intrinsic value; moral duty to future generations
The Evil Quartet
Four forces drive biodiversity loss, coined by Jared Diamond.
Current extinction rate 100–1000× pre-human background
- Habitat loss & fragmentation = MOST important cause
- Over-exploitation drove Steller’s sea cow & passenger pigeon extinct
- Alien: Nile perch wiped out Lake Victoria cichlids; Lantana, Eichhornia
Diversity & Stability
Communities with more species are more stable and more productive.
Tilman’s plots: more species → less variation + higher productivity
- Stability = low year-to-year variation + resistance to disturbance & invasion
- Each lost rivet (species) weakens the plane; wing rivets = key species
- Losing key species threatens the whole ecosystem even if early loss seems harmless
In-situ Conservation
Protecting species in their natural habitat — the preferred, cost-effective approach.
India has 3 hotspots: Western Ghats–Sri Lanka, Indo-Burma, Himalaya
- Hotspots: <2% of land but could prevent up to 30% of extinctions
- Biosphere reserve zones: core (no human activity) → buffer → transition
- Sites: biosphere reserves, national parks, sanctuaries, sacred groves
Ex-situ Conservation
Conserving threatened species outside their natural habitat as a specialised backup.
Cryopreserved gametes/seeds kept viable AND fertile
- Captive breeding then reintroduction to the wild
- Convention on Biological Diversity — Rio Earth Summit, 1992
- Johannesburg 2002: 190 countries pledged to cut loss rate by 2010
📝 Practice Biodiversity and Conservation — 10 NEET PYQs
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Frequently Asked Questions
The three levels are genetic diversity (variation in genes within a single species), species diversity (the variety of species in a region) and ecological or ecosystem diversity (the variety of ecosystems and habitats in an area). The term biodiversity was popularised by Edward Wilson.
The species-area relationship, studied by Alexander von Humboldt, shows that within a region species richness increases with the area sampled but only up to a limit. On a log-log scale the relationship is a straight line described by the equation log S = log C + Z log A, where Z is the slope or regression coefficient.
The Evil Quartet, a term coined by Jared Diamond, refers to the four major causes of biodiversity loss: habitat loss and fragmentation (the most important cause), over-exploitation, alien species invasions, and co-extinctions.
In-situ conservation protects species in their natural habitats, for example through biosphere reserves, national parks, sanctuaries and biodiversity hotspots. Ex-situ conservation protects threatened species outside their natural habitats, for example in zoos, botanical gardens, seed banks and through cryopreservation and in-vitro fertilisation.
The Rivet Popper Hypothesis, proposed by Paul Ehrlich, compares an ecosystem to an aeroplane held together by rivets, where each rivet represents a species. Losing a few rivets (species) may not be immediately dangerous, but the continued loss of more species weakens the ecosystem until it can collapse, especially if key species are lost.