Question
Explain the three levels of biodiversity — genetic, species, and ecosystem diversity. Give examples of each. Why is genetic diversity important for the survival of a species?
(NEET + CBSE Board pattern — definitions + reasoning)
Solution — Step by Step
| Level | What It Measures | Example |
|---|---|---|
| Genetic diversity | Variation in genes within a species | Different varieties of rice (Basmati, Jasmine, wild rice) — same species, different genes |
| Species diversity | Number and variety of species in a region | Western Ghats has more amphibian species than Eastern Ghats |
| Ecosystem diversity | Variety of ecosystems in a geographic area | India has deserts, rainforests, mangroves, coral reefs, alpine meadows |
Genetic diversity is the raw material for evolution. A population with high genetic diversity has individuals with different alleles — some may be resistant to a new disease, some may tolerate drought, some may handle temperature changes. When the environment changes, at least some individuals in a genetically diverse population will survive and reproduce.
A population with low genetic diversity (like cheetahs) is vulnerable — a single disease can wipe out the entire population because all individuals are similarly susceptible.
Example: India has over 50,000 genetically different strains of rice and 1,000 varieties of mango — this genetic diversity is a national treasure for food security.
- Total species described globally: approximately 1.5 million (estimated 5-30 million exist)
- India’s contribution: about 8.1% of global species diversity — making India one of the 12 mega-diversity countries
- Among animals, insects are the most species-rich group (over 70% of all animal species)
- Among plants, angiosperms dominate (over 300,000 species)
The species-area relationship:
where = species count, = area, = regression coefficient (typically 0.1-0.3 for small areas, 0.6-1.2 for large areas/continents).
graph TD
A[Biodiversity] --> B["Genetic Diversity"]
A --> C["Species Diversity"]
A --> D["Ecosystem Diversity"]
B --> B1["Variation within a species"]
B --> B2["Rice varieties, mango varieties"]
C --> C1["Number of species in a region"]
C --> C2["India: 8.1% of global species"]
D --> D1["Variety of habitats"]
D --> D2["Deserts, forests, coral reefs"]
style A fill:#fbbf24,stroke:#000,stroke-width:2px
style B fill:#86efac,stroke:#000
style C fill:#93c5fd,stroke:#000
style D fill:#f9a8d4,stroke:#000Why This Works
The three levels represent a hierarchy: genes make up species, species make up ecosystems. Loss at any level affects the others — losing genetic diversity weakens a species, losing a species can destabilise an ecosystem, and losing an ecosystem wipes out all species within it.
This is why conservation must operate at all three levels simultaneously — protecting genes (through seed banks and gene pools), species (through protected areas), and ecosystems (through landscape-level planning).
Common Mistake
Students confuse species diversity with species richness. Species richness is simply the count of species in an area. Species diversity also includes relative abundance (evenness) — a forest with 10 equally common species is more diverse than one with 10 species where one dominates 90% of the population. NEET sometimes tests this distinction.
For NEET, memorise: India is a mega-diversity country with 4 biodiversity hotspots — Western Ghats, Eastern Himalayas, Indo-Burma, and Sundaland. A hotspot must have at least 1500 endemic vascular plant species and have lost at least 70% of its original habitat.