Levels of biodiversity, species count, latitudinal gradient, species–area relationship, causes of biodiversity loss (the Evil Quartet), and in situ / ex situ conservation — with SVG diagrams, a species–area calculator, MCQs, A-R and PYQs.
Term popularised by sociobiologist Edward Wilson for the combined diversity at all levels of biological organisation — from macromolecules to biomes.
| Level | Meaning | Example |
|---|---|---|
| Genetic diversity | Variation within a single species over its range | Rauwolfia vomitoria in different Himalayan ranges varies in potency/concentration of reserpine; India has >50,000 genetically different rice strains and 1,000 mango varieties |
| Species diversity | Diversity at species level | Western Ghats have greater amphibian species diversity than Eastern Ghats |
| Ecological diversity | Diversity at ecosystem level | India (deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, alpine meadows) vs Norway |
It took millions of years of evolution to build this diversity, but it could be lost in less than two centuries at present loss rates.
(a) Evolutionary time — tropics were undisturbed for millions of years (temperate regions had glaciations). (b) Constant, predictable, less seasonal environment → niche specialisation. (c) More solar energy → higher productivity → more diversity.
| Argument | Points |
|---|---|
| Narrowly utilitarian | Direct economic benefits: food, firewood, fibre, construction material, industrial products (tannins, lubricants, dyes, resins, perfumes), medicines. >25% of drugs sold worldwide are plant-derived; 25,000 plant species used in traditional medicine. Bioprospecting = exploring molecular, genetic and species-level diversity for economically important products. |
| Broadly utilitarian | Ecosystem services: the Amazon produces ~20% of Earth's oxygen; pollination by bees, bumblebees, birds, bats; aesthetic pleasures (intangible benefits). |
| Ethical | Every species has intrinsic value; moral duty to care for them and pass on our biological legacy in good order to future generations. |
| Point | In situ (on site) | Ex situ (off site) |
|---|---|---|
| Idea | Protect the whole ecosystem in nature — 'save the entire forest to save the tiger'; protects biodiversity at all levels | Threatened organisms are taken out of the natural habitat and given special care; needed when species face very high risk of extinction in the wild |
| Methods | Biodiversity hotspots, biosphere reserves, national parks, wildlife sanctuaries, sacred groves | Zoological parks, botanical gardens, wildlife safari parks; cryopreservation of gametes; in vitro fertilisation; tissue culture; seed banks |
Q1. For a region, the species–area slope is Z = 0.15. If the area becomes 10 times larger, by what factor does species richness increase?
S = C·AZ (log S = log C + Z log A).
S₂/S₁ = (A₂/A₁)Z = 100.15.
100.15 ≈ 1.41 → about 41% more species, although area rose 10-fold.
Q2. Differentiate between in situ and ex situ conservation with two examples each.
Conservation in the natural habitat, protecting the whole ecosystem — national parks, sanctuaries, biosphere reserves, sacred groves.
Conservation outside the natural habitat for threatened species — zoological parks, botanical gardens, seed banks, cryopreservation.
Q3. Give three hypotheses to explain why the tropics show the greatest species richness.
Tropics remained undisturbed for millions of years (no glaciation) → long evolutionary time for speciation.
Less seasonal, more constant and predictable environment → niche specialisation.
More solar energy → higher productivity → indirectly more diversity.
(A) Both true, R explains A. (B) Both true, R does NOT explain A. (C) A true, R false. (D) A false, R true.
Q. Name the three important components of biodiversity.
Genetic diversity, species diversity and ecological (ecosystem) diversity.
Q. What is the significance of the slope of the regression in a species–area relationship?
In log S = log C + Z log A, Z is the slope: 0.1–0.2 for regions of any taxon (similar across groups), but 0.6–1.2 for continents. A steeper slope means species richness rises much faster as area increases (larger areas add whole new habitats and biota).
Q. What are the major causes of species losses in a geographical region?
The Evil Quartet: (i) habitat loss and fragmentation; (ii) over-exploitation; (iii) alien species invasions; (iv) co-extinctions — with one example each (rain forests; Steller's sea cow; Nile perch; host fish and its parasites).
Q. What are sacred groves? What is their role in conservation?
Tracts of forest set aside by cultural and religious traditions where all trees and wildlife are venerated and totally protected (Meghalaya, Aravalli, Western Ghats, Madhya Pradesh). They are in situ conservation sites — in Meghalaya the last refuge of many rare and threatened plants.
Q. How is biodiversity important for ecosystem functioning?
Communities with more species show less year-to-year variation in biomass, higher productivity and greater resistance to invasion (Tilman). Biodiversity loss lowers plant production and resistance to drought. Ehrlich's rivet popper hypothesis: losing key species weakens the ecosystem like removing rivets from a plane's wings.