Biodiversity Study Guide

Biodiversity Study Guide

What is Biodiversity?

• Biodiversity is a combination of the Greek word Bios (=life) and the Latin word Diversitas (= variety).

• Biodiversity means the Variety of life in ecology. Biodiversity refers to the diversity (number & variety of species) of plant and animal life within a region.

• In this way, we can say, as far as the extent of the biosphere, there is biodiversity, i.e., variety of life. Inversely, as far as variety of life is possible, up to that extent, there is a biosphere.

• In our biosphere, immense diversity exists.

The known and described number of species of all organisms on the earth is approximately. 1.7-1.8 million, which is fewer than 15% of the actual number.

Levels of Biodiversity

The term Biodiversity was first coined by Waller G. Rosen (b.1929) in 1985, but this term is popularized by the American sociobiologist Edward Osborne (E.O.) Wilson (1929-2021), to describe the combined diversity at all hierarchical levels of biological organisation.

• E.O. Wilson is revered as the Father of Biodiversity.

• Biological diversity includes three important hierarchical levels—Genetic, Species and Community & and Ecosystem diversity.

These levels of biodiversity are interrelated, yet distinct enough to be studied separately.

1. Genetic Diversity

• Genetic diversity refers to the variation of genes within species.

• Each species stores an immense amount of genetic information.

  • For example, the number of genes is about 35,000 to 45,000 in Homo sapiens.

• India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango.

• The amount of genetic variation is the basis of speciation (the evolution of new species).

• It has a key role in the maintenance of diversity at the species and community levels.

• Genetic diversity within a species often increases with environmental variability.

2. Species Diversity

• Species diversity refers to the variety of species within a region.

  • For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

• Species are distinct units of diversity, each playing a specific role in an ecosystem.

• Therefore, the loss of species has consequences for the ecosystem as a whole.

3. Community and Ecosystem Diversity

Alpha Diversity

• Diversity of organisms within-community diversity is called Alpha diversity.

• Alpha diversity refers to the diversity of organisms sharing the same community/habitat.

Beta Diversity

• Diversity of organisms between communities (i.e., in an ecosystem) is called Beta diversity.

Gamma Diversity

• Diversity of habitat over the total landscape or biome is called Gamma diversity.

Biodiversity in the World

Estimates and Reports

• The World Conservation Union—WCN (formerly known as the International Union for the Conservation of Nature and Natural Resources—IUCN) issues biodiversity-related reports from time to time.

• But we have no clear idea of how many species are yet to be discovered and described.

• Estimates vary widely, and many of them are only educated guesses.

Global Species Diversity

• Some extreme estimates range from 20 to 50 million, but a more conservative and scientifically sound estimate made by Australian ecologist Rokeri May (1936-2020) places the global species diversity at about 7 million.

• More than 70% of all the species recorded are animals, while plants (including algae, fungi, angiosperms, etc.) comprise no more than 22% of the total.

• Among animals, insects are the most species-rich taxonomic group, making up more than 70% of the total.

• Among plants, fungi and angiosperms are the most species-rich taxonomic groups, making up about 14% and 14% respectively of the total.

Patterns of Variation

• Biodiversity varies with changes in latitude and altitude.

• In general, species diversity increases as we move away from the poles towards the equator.

• Similarly, we generally notice a decrease in species diversity from lower to higher altitudes on a mountain.

• Notably, the more complex and heterogeneous the physical environment, the more complex and diverse the flora and fauna.

Biodiversity in India

India’s Global Status

• Although India has only 2.4% of the world's land area, its share of the global species diversity is an impressive 8.1%.

• That is what makes our country one of the 12 mega diverse countries of the world.

• The largely tropical Amazonian rainforest in South America has the greatest biodiversity on earth.

Undiscovered Species

• If we accept May's global estimates, only 22% of the total species have been recorded so far.

• Applying this proportion to India's diversity figures, we estimate that there are probably more than 1 lac plant species and 3 lac animal species yet to be discovered and described.

• Nature's biological library is burning even before we catalogue the titles of all the books stocked there.

Biogeographical Regions

• In India, we are endowed with a rich diversity of biogeographically distinct regions due to varying physical conditions and species groupings.

• Among the biogeographical regions, the Deccan Peninsula has the most extensive coverage of the Indian landmass (42%).

• The most biodiversity-rich zones, the North-East, account for 5.2% and the Western Ghats account for 4% of the geographical area.

Endemic Species

• A large number of species found in these zones are endemic or exclusive to India.

• About 33% of flowering plants, 53% of freshwater fish, 60% of amphibians, 36% of reptiles, and 10% of mammals are endemic to our country.

• The endemics are concentrated mainly in the North-East, Western Ghats, North-West Himalaya, and Andaman & Nicobar Islands.

Final Thoughts

Biodiversity is not just a scientific term; it is the foundation of life on Earth. From genetic variation within species to the richness of ecosystem diversity, each level plays a critical role in maintaining the balance of nature. The global distribution of biodiversity shows that life thrives more in certain regions, especially around the equator, while India stands out as one of the 12 megadiverse countries of the world.

Our rich flora and fauna not only support ecological stability but also contribute to human survival through resources, medicine, and food. However, species loss, habitat destruction, and climate change are major threats that could disrupt this balance forever.

Protecting endemic species and conserving hotspots like the Western Ghats and North-East is no longer optional—it’s a necessity. The fact that more than 85% of Earth’s species remain undiscovered is both fascinating and alarming.

The carbon balance, food chains, and ecosystem services all depend on this natural variety. In short, biodiversity is life’s safety net, and safeguarding it is safeguarding our future. Every action we take today will decide the health of our planet for generations to come.