Introduction
Biodiversity refers to the variety and variability of living organisms present on Earth. It includes diversity within species, between species, and among ecosystems. Biodiversity is essential for maintaining ecological balance and supporting life on our planet.
The term "Biodiversity" was popularized by Walter G. Rosen (1986).
For NEET, this chapter is highly important because questions are frequently asked from biodiversity patterns, species richness, biodiversity loss, hotspots, and conservation strategies.
What is Biodiversity?
Biodiversity is the sum total of all living organisms and the ecological complexes of which they are a part.
It includes:
- Plants
- Animals
- Microorganisms
- Ecosystems
Levels of Biodiversity
1. Genetic Diversity
Diversity present within a species.
Examples:
- Different varieties of rice in India
- Different breeds of dogs
- Genetic variations in humans
Importance:
- Helps species adapt to changing environments.
- Provides raw material for evolution.
2. Species Diversity
Diversity of species within a region.
Examples:
- Western Ghats have a large number of plant and animal species.
- Tropical rainforests show high species diversity.
3. Ecological Diversity
Diversity at the ecosystem level.
Examples:
- Forests
- Grasslands
- Deserts
- Wetlands
- Marine ecosystems
Biodiversity in India
India is one of the world's megadiverse countries.
Important Facts:
- India has only about 2.4% of the world's land area.
- It harbors approximately 8.1% of the global species diversity.
- Around 45,000 species of plants are found in India.
- More than 90,000 species of animals have been identified.
India is among the 12 megadiversity nations of the world.
Patterns of Biodiversity
1. Latitudinal Gradient
Species diversity decreases from the equator towards the poles.
Examples:
- Tropical regions possess more biodiversity than temperate and polar regions.
- Tropical rainforests are highly species-rich.
Reasons:
- Stable climate
- Greater solar energy
- Long evolutionary history
2. Species-Area Relationship
Proposed by:
Alexander von Humboldt
Within a region, species richness increases with increasing explored area.
Relationship:
S = CAᶻ
Where:
- S = Species richness
- C = Constant
- A = Area
- Z = Regression coefficient
Important for NEET:
- Value of Z generally ranges from 0.1 to 0.2.
- For very large areas like continents, Z may range from 0.6 to 1.2.
Importance of Biodiversity
Ecological Importance
- Maintains ecosystem stability.
- Supports nutrient cycling.
- Helps in pollination.
- Regulates climate.
Economic Importance
- Food resources
- Medicines
- Timber
- Fuelwood
- Industrial products
Ethical and Aesthetic Importance
Every species has an intrinsic value and a right to exist.
People also derive recreational and cultural benefits from biodiversity.
Loss of Biodiversity
The current rate of species extinction is much higher than natural extinction rates.
Scientists estimate that thousands of species are being lost every year.
Major Causes of Biodiversity Loss
According to NCERT, the major causes are known as the "Evil Quartet."
1. Habitat Loss and Fragmentation
Most important cause of biodiversity loss.
Examples:
- Deforestation
- Urbanization
- Construction activities
Effects:
- Reduction in species population
- Increased risk of extinction
2. Over-Exploitation
Excessive use of biological resources.
Examples:
- Overfishing
- Excessive hunting
- Unsustainable logging
3. Alien Species Invasions
Introduction of non-native species that threaten native biodiversity.
Examples:
- Parthenium (Congress grass)
- Eichhornia (Water hyacinth)
- African catfish
4. Co-Extinction
When one species becomes extinct, species associated with it may also disappear.
Examples:
- Host-parasite relationships
- Plant-pollinator relationships
Biodiversity Conservation
Conservation means protection, preservation, and management of biodiversity for present and future generations.
Types of Conservation
1. In-Situ Conservation
Conservation of species in their natural habitat.
Protected Areas
National Parks
Areas reserved for wildlife protection.
Examples:
- Jim Corbett National Park
- Kaziranga National Park
Wildlife Sanctuaries
Protected areas where wildlife is conserved.
Biosphere Reserves
Large protected areas that conserve biodiversity and ecosystems.
Examples:
- Nilgiri Biosphere Reserve
- Nanda Devi Biosphere Reserve
Biodiversity Hotspots
Regions with:
- High species richness
- High endemism
- Significant habitat loss
Concept introduced by:
Norman Myers
Hotspots in India:
- Western Ghats and Sri Lanka
- Indo-Burma
- Himalaya
- Sundaland (Nicobar Islands)
2. Ex-Situ Conservation
Conservation outside natural habitats.
Examples:
- Botanical gardens
- Zoological parks
- Seed banks
- Tissue culture
- Cryopreservation
Advantages:
- Protection of endangered species
- Controlled breeding programs
Biodiversity Hotspots
A biodiversity hotspot must satisfy:
- At least 1,500 endemic vascular plant species.
- Loss of at least 70% of original habitat.
Hotspots are priority areas for conservation efforts.
International Efforts for Conservation
Earth Summit (1992)
Held in:
Rio de Janeiro
Objectives:
- Sustainable development
- Biodiversity conservation
Convention on Biological Diversity (CBD)
Major goals:
- Conservation of biodiversity
- Sustainable use of biological resources
- Fair sharing of benefits from genetic resources
Important NCERT Facts for NEET
- India is a megadiverse nation.
- Tropical regions show maximum biodiversity.
- Alexander von Humboldt proposed the species-area relationship.
- Norman Myers introduced the concept of biodiversity hotspots.
- Habitat loss is the major cause of biodiversity decline.
- Evil Quartet includes habitat loss, over-exploitation, alien species invasion, and co-extinction.
- In-situ conservation protects organisms in their natural habitat.
- Ex-situ conservation protects organisms outside their natural habitat.
- Biodiversity hotspots are regions of high endemism and high habitat loss.
NEET Quick Revision Table
| Topic | Key Point |
|---|---|
| Biodiversity | Variety of living organisms |
| Genetic Diversity | Diversity within species |
| Species Diversity | Diversity among species |
| Ecological Diversity | Diversity among ecosystems |
| Megadiversity Nation | India |
| Species-Area Relationship | Humboldt |
| Biodiversity Hotspot | Norman Myers |
| Evil Quartet | Four major causes of biodiversity loss |
| In-Situ Conservation | Natural habitat protection |
| Ex-Situ Conservation | Conservation outside habitat |
Frequently Asked NEET Questions
Which is the most important cause of biodiversity loss?
Habitat loss and fragmentation.
Who proposed the species-area relationship?
Alexander von Humboldt.
What are biodiversity hotspots?
Regions with high endemism and severe habitat destruction.
What is the difference between in-situ and ex-situ conservation?
In-situ conservation occurs in natural habitats, whereas ex-situ conservation occurs outside natural habitats.
Why is biodiversity important?
It maintains ecosystem stability, supports human needs, and ensures sustainable development.
Conclusion
Biodiversity is the foundation of ecological stability and human survival. Understanding biodiversity patterns, causes of biodiversity loss, hotspots, and conservation strategies is essential for NEET preparation. Focus especially on the Evil Quartet, biodiversity hotspots, species-area relationship, and conservation methods, as these topics are frequently tested in NEET examinations.
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