Maarg Manthan · Topic 6.1

Definition and Types of Biodiversity (Genetic, Species, Ecosystem)

Environment & Ecology › Biodiversity Basics and Classification · Topic 6.1

Biodiversity, or biological diversity, is the variety of life on Earth at all levels, from genes to species to ecosystems, and the ecological processes of which they are part. The term was popularised by Walter Rosen in 1985, and the Convention on Biological Diversity (1992) defines it as the variability among living organisms from all sources, including terrestrial, marine and other aquatic ecosystems, and the ecological complexes of which they are part. It has three levels: genetic diversity, the variation of genes within a species; species diversity, the variety of species in a region; and ecosystem diversity, the variety of habitats, communities and ecological processes. About 1.7 to 2 million species are described, while the estimated total ranges from several million to about 8.7 million. India is one of the 17 megadiverse countries.

5 min read · UPSC Prelims · Environment & Ecology · Biodiversity Basics and Classification

At a Glance

Levels Genetic, species, ecosystem
Term popularised Walter Rosen, 1985
Defined in CBD, 1992
Described species About 1.7 to 2 million
Megadiverse countries 17, including India
Exam link UPSC Prelims, Environment & Ecology: Biodiversity Basics and Classification

Where Does It Fit?

This is the first topic of the macro on biodiversity basics. It sets out what biodiversity is and the three levels at which it is measured, before the patterns, classifications and hotspots that follow. Previous topic: Phosphorus Cycle and Human Influence on It. Next topic: Patterns of Biodiversity.

What Are the Three Types of Biodiversity?

Type	Meaning and examples
Genetic diversity	Variation in genes within a species. Example: over 50,000 rice varieties and about 1,000 mango varieties in India; different forms of Rauwolfia vomitoria in potency of reserpine
Species diversity	Variety of species in an area, measured by richness (number of species) and evenness (relative abundance). Western Ghats amphibians show higher species diversity than the Eastern Ghats
Ecosystem diversity	Variety of ecosystems in a region, such as deserts, forests, wetlands, mangroves, coral reefs and grasslands. India has a very wide range
Alpha diversity	Diversity within a particular habitat or community (local)
Beta diversity	Change in species composition between habitats along a gradient
Gamma diversity	Total diversity of a large region or landscape, combining alpha and beta
Functional diversity	Variety of ecological roles that species play

How Much Biodiversity Does the World and India Have?

Global species: about 1.7 to 2 million described, with estimates of the total at about 8.7 million eukaryote species and many more microbes
Insects: the largest group, more than half of known species
Megadiverse countries: 17 countries hold the majority of the world’s species, including Brazil, Indonesia, Colombia, China, India, Mexico, Australia and South Africa
India’s share: about 2.4 percent of land area but around 7 to 8 percent of recorded species
India’s flora and fauna: over 50,000 plant species and over 100,000 animal species recorded; check the latest Botanical and Zoological Survey of India figures
Biogeographic zones: India has ten biogeographic zones, and four hotspots in whole or part
Endemism: many species occur only in India, such as in the Western Ghats
Domesticated diversity: India is a centre of origin of rice, mango, banana, brinjal, cucumber and many spices

What Else Should You Remember?

Walter Rosen: coined the shortened word biodiversity at the 1986 National Forum on BioDiversity in Washington
Edward O. Wilson: popularised the word in his writing
Species richness: simple count of species
Species evenness: how equal the abundances are
Shannon index: a common measure combining richness and evenness
Simpson index: measures dominance
Endemic species: found only in one region
Cosmopolitan species: widely distributed across regions
Keystone species: have a large effect on the ecosystem relative to numbers
Indicator species: signal the health of the ecosystem
Flagship species: charismatic species used to gain support, such as the tiger
Umbrella species: protecting them protects many others
Biodiversity in the tropics: high diversity, as in rainforests and coral reefs
Agrobiodiversity: diversity of crops, livestock and their wild relatives
Crop wild relatives: wild plants related to crops, a source of useful genes
Landraces: traditional farmer-developed crop varieties
Biological Diversity Act, 2002 Key power Approval for foreign access Lower tiers SBBs…">National Biodiversity Authority: set up in 2003 in Chennai under the Biological Diversity Act, 2002
People’s Biodiversity Register: local records of biological resources and knowledge kept by biodiversity management committees
International Day for Biological Diversity: 22 May
Link to next: see Patterns of Biodiversity
Link to hotspots: see Biodiversity Hotspots
Link to law: see Environmental Acts, Policies and EIA macro
Caution: species totals are estimates and change as new species are described
Taxonomic bias: vertebrates and flowering plants are better known than fungi, insects and microbes
Unknown diversity: the deep sea and soil microbial life remain poorly known
Exam hint: learn the three levels with one example each
Convention on Biological Diversity: adopted at the Rio Earth Summit in 1992 and in force from 1993, it has three aims: conservation of biodiversity, sustainable use of its components and fair sharing of benefits from genetic resources; India is a party

Why Does It Matter for the Exam?

Levels: genetic, species, ecosystem
Measures: alpha, beta, gamma
India: megadiverse, 10 zones
Current affairs link: 22 May theme and National Biodiversity Authority
Common errors: confusing species richness with species evenness, or alpha with gamma diversity

As an analytical point, biodiversity is not just a count of species but includes genes and ecosystems, and each level needs its own conservation approach. India’s rich agrobiodiversity and endemism make its stewardship globally important.

Why Is This Topic Important?

Levels Genes, species, ecosystems
Measures Alpha, beta, gamma
India Megadiverse

What Came Next?

The next topic covers patterns of biodiversity such as the latitudinal gradient and species-area relationship. Next topic: Patterns of Biodiversity.

Key People and Terms

Biodiversity Variety of life
Species richness Number of species
Endemic Found only in one region
Alpha diversity Local diversity
Gamma diversity Regional diversity
Landrace Traditional crop variety

Exam Corner

Points to Remember

Three levels: genes, species, ecosystems.
Term popularised by Walter Rosen.
India is megadiverse.
Alpha is local, gamma is regional.
Day: 22 May.

Do Not Confuse With

Species richness and evenness Count versus equality of abundance
Alpha and beta diversity Within habitat versus between habitats
Endemic and native species Only here versus belonging here

Memory Hook

Genes in a species, species in a place, places in a landscape: three layers of life.

Mains Angle

Questions ask for levels and examples. These points help.

Levels Three
India Megadiverse
Measures Indices

A Question You May Face

An original practice question, not a past paper question.

“What is biodiversity? Explain its different levels with examples and discuss why India is called a megadiverse country.”

How to Answer

Define Variety of life.
Levels Three.
Measure Alpha, beta, gamma.
India Megadiverse.

GS Relevance

Prelims: three levels of diversity, definitions, megadiverse countries. GS Paper 3: conservation and biodiversity.

Frequently Asked Questions

What is biodiversity?

Biodiversity is the variety of life on Earth, including the variation of genes within species, the variety of species within and across regions, and the variety of ecosystems and ecological processes. It is the basis of ecosystem services such as food, clean water, pollination and climate regulation, on which human well-being depends.

What are the three levels of biodiversity?

The three levels are genetic diversity, which is the variation of genes within a species such as different rice varieties, species diversity, which is the variety of species in an area, and ecosystem diversity, which is the variety of habitats such as forests, wetlands and deserts within a region.

What is the difference between alpha, beta and gamma diversity?

Alpha diversity is the species diversity within a single habitat or community. Beta diversity is the difference in species composition between habitats or along an environmental gradient. Gamma diversity is the total species diversity of a larger region or landscape, resulting from alpha diversity and beta diversity together.

What is a megadiverse country?

A megadiverse country is one that holds a very large share of the world's species and a high number of endemic species. Seventeen countries, among them Brazil, Indonesia, China, Mexico, Australia, South Africa and India, are classed as megadiverse and together contain the majority of the world's biodiversity.

Why is India rich in biodiversity?

India has a wide range of climates, from tropical to alpine, varied landforms including the Himalaya, Western Ghats, deserts, wetlands and a long coastline with islands. It also lies in three biogeographic realms, has four biodiversity hotspots in whole or part, and is a centre of origin of many crops.

PYQ Practice — Statement Analysis

1 Genetic diversity refers to variation within a species.

True

E.g., rice varieties.

2 Gamma diversity is diversity within a single habitat.

False

That is alpha diversity.

3 India is one of the megadiverse countries.