Board exam focus — Biodiversity and Conservation (CBSE & HBSE)

CBSE focuses on levels of biodiversity, patterns of biodiversity (latitudinal gradients), biodiversity hotspots, threats (HIPPO), extinction, in situ and ex situ conservation, and international conventions (CBD). HBSE emphasises definitions, types of biodiversity, species loss causes, hotspot criteria, and conservation methods.

Types and Patterns of Biodiversity

Biodiversity: Definition and Levels

Biodiversity (a contraction of biological diversity) refers to the variety of life on Earth at all its levels — from genes to ecosystems. The term was popularised by E.O. Wilson (Harvard entomologist and "ant man") in the 1980s.

Earth supports an estimated 8.7 million species (±1.3 million) — only ~1.5 million described. India has about 8% of global species on 2.4% of the world's land.

Three Levels of Biodiversity:

1. Genetic Diversity:

• Variety of genes and alleles within a species and between populations of the same species
• Examples: 50,000 genetically distinct rice varieties in India; 1,000 varieties of mango
• Even within a species (e.g., humans), different populations have different allele frequencies at thousands of loci
• Basis for evolution (provides raw material for natural selection)
• Agricultural importance: genetic diversity in crop wild relatives enables breeding for disease resistance, drought tolerance, etc.
• High genetic diversity = greater adaptability to environmental change

2. Species Diversity:

• Variety of different species in a region
• Measured by:
• Species richness: total number of species in a defined area
• Relative abundance: how evenly individuals are distributed among species
• Species evenness: uniformity of distribution
• Shannon diversity index (H'): combines richness and evenness: H' = -Σ (pi × ln pi) where pi = proportion of species i
• Example: A forest may have higher species richness (more species) but lower evenness if one species dominates; an evenness measure corrects for this

3. Ecosystem Diversity:

• Variety of ecosystems in a region; diversity of habitats, ecological communities, and ecological processes
• India has: tropical rainforests, deciduous forests, grasslands, deserts (Thar), wetlands (Sundarbans), mangroves, coral reefs, alpine tundra, rivers, lakes, estuaries
• Includes the complex ecological processes that maintain them

Patterns of Biodiversity

1. Latitudinal Diversity Gradient:

• Species richness increases from poles to tropics — the most general and robust pattern in ecology
• Tropical regions (equatorial) have far more species than temperate or polar regions
• Global pattern: Colombia (5°N) has 1,700+ bird species; New York (40°N) has ~105; Greenland (70°N) has ~56
• Example: Mammals in tropics (Amazon, Congo, SE Asia) vastly outnumber those in temperate or Arctic regions

Explanations for latitudinal gradient:

1. Longer evolutionary history (tropics were neither glaciated nor dramatically changed by ice ages → more time for speciation)
2. Greater solar energy input → higher photosynthetic productivity → more food → supports more species
3. Greater ecological complexity → more niches → more species
4. Lower seasonality (stable climate year-round) → more specialised species possible (narrower niches)
5. Less severe winters → more plant diversity → more animal diversity (plant-animal coevolution)
6. Larger area (most tropical biomes are large) → island biogeography effect

2. Species-Area Relationship: Z.E. Arrhenius (1921): the relationship between the area of a habitat and the number of species it supports. S = c × A^z (or log S = log c + z × log A) Where: S = number of species; A = area; z = slope (species-area regression coefficient); c = constant depending on the taxonomic group

• In small islands (or isolated habitats): z = 0.1–0.2 (small slope — fewer new species per unit area increase)
• For species on different continents (larger regions): z = 0.6–1.2 (steeper slope)
• Implication: when habitat is fragmented (reduced area), a predictable decline in species richness occurs (deforestation causes species loss)

India's Biodiversity

India is one of the 17 mega-biodiversity countries (or mega-diverse countries) — nations that together harbour more than 70% of Earth's biodiversity. Others include Brazil, Colombia, Indonesia, Malaysia, Mexico, Australia, South Africa, Peru, Madagascar, China, etc.

India's biodiversity statistics:

• ~8% of world's species on ~2.4% of land area
• 45,000+ plant species (11,000 higher plants); ~18,000 endemic plant species
• 91,000+ animal species (6.5% of world's fauna)
• 13 major forest types; 16 major climatic types

Western Ghats: 163 frog species (many endemic); 508 bird species; 325 butterfly species

Eastern Himalayas: Snow leopard, Red panda; high plant endemism

Endemism: Species found ONLY in a particular area (not found anywhere else).

Biodiversity Hotspots and Threats

Biodiversity Hotspots

The concept of biodiversity hotspots was proposed by Norman Myers (1988, updated 1990 and 2000) to identify regions of particularly high biodiversity combined with severe threat.

Criteria for a Biodiversity Hotspot (Myers' two-part definition):

1. High endemism: must contain at least 1,500 endemic vascular plant species (>0.5% of world's ~300,000 plant species)
2. Significant habitat loss: must have lost at least 70% of its original habitat (i.e., only 30% or less of original vegetation remains intact)

Currently: 36 biodiversity hotspots worldwide (Conservation International, latest count)

Two hotspots in India:

1. Western Ghats + Sri Lanka: Continuous mountain range along west coast of India (Kerala, Karnataka, Tamil Nadu, Goa, Maharashtra, Gujarat). Home to: 5,000+ flowering plant species (1,700 endemic); 139 mammal species; 508 bird species (17 endemic); 179 amphibian species (163 endemic — all three families of caecilians present). Major threats: agriculture, coffee and tea plantations, dams, quarrying, invasive species. Less than 10% original vegetation remains in India portion.

1. Indo-Burma region (formerly Himalayan hotspot is part of this): Includes Eastern Himalayas, eastern India (northeast states), Bangladesh, Burma, Thailand, Cambodia, Laos, Vietnam, south China. One of the most biologically diverse regions on Earth. Major threats: deforestation, agriculture expansion, hunting, dam construction.

Other major hotspots: Mesoamerica (Central America), the Caribbean, Atlantic Forest (Brazil), Mediterranean Basin, Cape Floristic Region (South Africa), Sundaland (Indonesia/Malaysia), Madagascar, New Caledonia, Southwest Australia.

Threats to Biodiversity (HIPPO Framework)

The main causes of biodiversity loss are often summarised using the acronym HIPPO (or HIPPE):

H — Habitat loss and degradation (most important cause globally):

• Conversion of natural habitats to agricultural land (biggest driver in tropics — 80% of species loss attributed to habitat loss)
• Urbanisation and infrastructure development
• Deforestation: tropical forests reduced by 1.5 million km²/decade; ~70% of land animals and plants live in forests
• Wetland drainage, coral reef destruction, grassland ploughing
• Habitat fragmentation: large continuous habitats broken into isolated fragments (reduces population size, increases edge effects, reduces dispersal)

I — Invasive species (second most important cause):

• Non-native (alien/exotic) species introduced to a new region, often accidentally, that compete with, predate on, or parasitise native species
• The Nile perch (Lates niloticus) introduced to Lake Victoria (Africa) caused extinction of >200 endemic cichlid fish species
• Lantana camara (introduced ornamental) → now invasive across South Asia (India), Africa, Australia → outcompetes native vegetation, reduces native plant diversity
• Parthenium hysterophorus (Congress grass/carrot weed) — introduced from North America → major invasive weed in India
• Invasive brown tree snake (Boiga irregularis) introduced to Guam → eliminated 12 out of 14 native forest bird species
• Invasive plants in India: Eichhornia crassipes (water hyacinth), Prosopis juliflora (mesquite), Mikania micrantha

P — Pollution:

• Air pollution: acid rain → forest and lake acidification → species loss; tropospheric ozone damages plants
• Water pollution: industrial effluents, agricultural runoff (pesticides, fertilisers) → eutrophication, bioaccumulation, species loss
• Noise pollution: affects communication in marine mammals (dolphins, whales), bats, birds
• Light pollution: disrupts migrating birds, sea turtle nesting, nocturnal animals
• Plastic pollution: entanglement and ingestion; microplastics

P — Population growth (human):

• Increasing human population → greater resource use → greater habitat conversion, water use, pollution
• Per capita consumption in developed nations also very high
• Currently 8 billion humans; projected 9.7 billion by 2050

O — Overexploitation:

• Overhunting: passenger pigeon (once 3-5 billion individuals in North America; extinct 1914 — hunted to extinction); dodo (extinct 1662); great auk (extinct 1844)
• Overfishing: Atlantic cod (Grand Banks) collapsed due to overfishing; bluefin tuna threatened
• Illegal wildlife trade: rhino horn, elephant ivory, shark fins, tiger bones, pangolins — second-largest illegal trade after drugs
• Bushmeat hunting in Africa
• Overgrazing by livestock → grassland degradation

Climate Change (Additional HIPPO factor — increasing importance):

• Shifting climate envelopes → species range shifts; some cannot shift fast enough → local extinction
• Coral bleaching: thermal stress on symbiotic algae (zooxanthellae) → expulsion → coral death
• Phenological mismatches: plants flower earlier; pollinators emerge at different time → decoupling
• Arctic/Antarctic species (polar bears, penguins) losing habitat

Co-extinctions: When a species becomes extinct, its obligate mutualists (pollinators, parasites, seed dispersers, hosts) may also go extinct — cascade of extinctions. A parasitic fig wasp goes extinct when its host fig tree goes extinct.

IUCN Red List Categories:

The International Union for Conservation of Nature (IUCN) Red List assesses extinction risk:

• Extinct (EX): no reasonable doubt that the last individual has died
• Extinct in the Wild (EW): survives only in captivity or as naturalised population outside historic range
• Critically Endangered (CR): very high risk of extinction in the wild
• Endangered (EN): high risk of extinction in the wild
• Vulnerable (VU): elevated risk of extinction if circumstances do not improve
• Near Threatened (NT): close to qualifying for VU
• Least Concern (LC): widespread and abundant

Conservation of Biodiversity

Importance of Biodiversity — Value Arguments

Direct use values:

• Food: we rely on ~10,000 plant species for food (most biodiversity is untapped potential; only ~200 species widely cultivated)
• Medicines: ~25% of all drugs contain plant-derived compounds; aspirin (from willow bark), morphine (from opium poppy), taxol (from Pacific yew — anti-cancer), quinine (from Cinchona bark — antimalarial), artemisinin (from sweet wormwood — antimalarial)
• Timber and fibre: construction, furniture, paper
• Industrial products: rubber, dyes, cosmetics, essential oils
• Genetic resources: wild relatives of crops for breeding programs

Indirect use values (Ecosystem services):

• Carbon sequestration and climate regulation
• Pollination (~35% of world food crops)
• Watershed protection and water purification
• Soil formation and erosion prevention
• Pest regulation by natural predators/parasites
• Buffering of storm events (mangroves, coral reefs)
• Aesthetic, recreational, and cultural values

Option value: preserving biodiversity for potential future uses (undiscovered medicines, biomimicry, etc.)

Existence value: ethical obligation to preserve other species irrespective of use to humans

Conservation Strategies

Two main approaches:

A. In Situ Conservation (On-site / within natural habitat):

Protecting entire ecosystems and natural habitats where species occur.

1. Protected Areas:

• Biosphere Reserves (BRs): Largest category; multiple use zones; core zone (strictly protected), buffer zone (research permitted), transition zone (limited human use); 18 in India; designated by UNESCO (Man and Biosphere Programme)
• Examples: Nilgiri BR (first, 1986), Sundarbans BR, Nanda Devi BR, Gulf of Mannar BR
• National Parks (NPs): Strictly protected; no human habitation or resource use; wildlife can move freely. 106 NPs in India.
• Examples: Jim Corbett (first NP, 1936), Kaziranga (one-horned rhinoceros), Periyar (tigers, elephants), Bandhavgarh, Gir (Asiatic lion)
• Wildlife Sanctuaries: Protection but some human activities permitted (no hunting). ~550 in India.
• Community Reserves and Conservation Reserves: new categories under Wildlife Protection Act 2002; community-managed

2. Biodiversity Hotspot Protection: Focusing limited resources on areas with highest concentration of endemic species and highest threat

3. Sacred Groves:

• Traditionally protected forest patches in or near villages
• Protected due to cultural, religious, or spiritual significance
• Examples in India: Khasi Hills (Meghalaya), Rajasthan, Western Ghats
• Often harbour rare and endemic species; provide ecosystem services to local communities
• Devvan/Dev van in Rajasthan; Orans in Rajasthan; Sarna in Jharkhand/Odisha; Kovils in Tamil Nadu

4. Protected Area Network (India): India has ~5% of its territory under legal protection (NPs + Sanctuaries + BRs + Conservation Reserves + Community Reserves)

B. Ex Situ Conservation (Off-site / outside natural habitat):

Species removed from natural habitat and maintained under managed conditions.

1. Zoological Gardens (Zoos):

• ~800 zoos worldwide maintain ~600,000 animals of ~15,000 species
• Captive breeding programs for endangered species: Indian rhinoceros (Guwahati Zoo), California condor, Arabian oryx, Black-footed ferret
• Education and public awareness
• Limitation: limited space; cannot maintain viable populations of all species; cannot replicate natural behaviour

2. Botanical Gardens:

• Ex situ conservation of plant species; propagation and reintroduction
• Royal Botanic Gardens (Kew, London): collections from worldwide; 27,000 accessions
• Indian Botanical Garden (Kolkata): oldest; important collections
• Some botanical gardens maintain seed banks

3. Seed Banks (Long-term storage of seeds):

• Seeds of crop varieties, crop wild relatives, endangered plants stored at low temperature (-20°C) and low humidity
• National Bureau of Plant Genetic Resources (NBPGR), New Delhi: seeds of ~400,000 crop accessions
• Svalbard Global Seed Vault (Norway): "Doomsday vault" — backup for world's seeds; ~1.5 million accessions
• Advantage: large number of genotypes stored in small space; very long-term (decades to centuries)
• Limitation: not suitable for non-orthodox/recalcitrant seeds (seeds of mango, jackfruit, cocoa, rubber — cannot be dried and frozen)

4. Cryopreservation:

• Storage of cells, tissues, gametes (sperm, eggs), embryos at ultra-low temperatures (liquid nitrogen, -196°C)
• Preserves biological material indefinitely
• Used for: rare animal semen (wildlife), endangered coral fragments, plant tissue cultures
• Frozen Zoo (San Diego Zoo): cells of thousands of animal species

5. DNA/Genomic Libraries (Genome Banks):

• Store genetic material as DNA
• Especially important for extinct or nearly extinct species
• Museum specimens, herbarium sheets — DNA can be extracted from ancient material

6. Captive Breeding and Reintroduction:

• Breed endangered species in captivity → reintroduce to restored habitat
• Successes: Arabian oryx (extinct in wild 1972; reintroduced 1982); California condor (from 27 individuals in 1987 to >500 today); Black-footed ferret

International Conventions

Convention on Biological Diversity (CBD, 1992):

• Signed at Earth Summit (Rio de Janeiro, 1992); entered into force 1993; ~196 parties
• Three objectives: (1) Conservation of biological diversity; (2) Sustainable use of biological diversity; (3) Fair and equitable sharing of benefits arising from use of genetic resources (ABS — Access and Benefit Sharing)
• Implements: National biodiversity strategies and action plans (NBSAPs)

Nagoya Protocol (2010):

• Supplementary agreement to CBD; operationalises the ABS objective
• Requires prior informed consent (PIC) from the country of origin; mutually agreed terms (MAT) for use of genetic resources; benefits shared with local communities

Convention on International Trade in Endangered Species (CITES, 1975):

• Regulates international trade in wild animals and plants
• Appendix I: species threatened with extinction; trade prohibited
• Appendix II: not necessarily threatened now, but trade must be controlled
• Appendix III: species protected in at least one country

Ramsar Convention (1971):

• Convention on Wetlands of International Importance; 42 Ramsar sites in India (largest number)

India's Biodiversity Laws:

• Wildlife Protection Act 1972 (amended 2022): protects wildlife; schedules I-VI; establishes NPs and Sanctuaries
• Forest Conservation Act 1980: requires central government approval for diversion of forest land
• Biological Diversity Act 2002: implements CBD in India; creates NBA (National Biodiversity Authority), SBBs (State Biodiversity Boards), BMCs (Biodiversity Management Committees)

Frequently asked questions

Are these Biodiversity and Conservation notes free?

Yes — the Biodiversity and Conservation notes for Biology (Class 12) on Siksha Sarovar are completely free to read, with no account required.

Do these notes follow CBSE and HBSE?

Yes. The Biodiversity and Conservation notes are NCERT-aligned and include guidance for both CBSE and Haryana Board (HBSE), with important questions and MCQs for revision.

What does the Biodiversity and Conservation chapter cover?

Concept explanations, key formulas and definitions, fully solved examples and board-pattern practice questions for Biodiversity and Conservation.