Biodiversity: concept and levels
Biodiversity, a term popularised by Edward Wilson, is the variety of life at all levels. Its three main levels are genetic, species and ecological diversity.
What is biodiversity?
Living things range from microbes to blue whales, and their variety exists at every level of organisation, from macromolecules in cells to biomes. The biologist Edward Wilson popularised the term biodiversity for this combined diversity at all levels. The three most important levels are genetic diversity, species diversity and ecological diversity.
The three levels of biodiversity
| Level | Meaning | Example |
|---|---|---|
| Genetic diversity | Variation in genes within a single species across its range | The medicinal plant Rauwolfia vomitoria in different Himalayan ranges differs in the potency and amount of reserpine it makes. India has more than 50,000 genetically different strains of rice and 1,000 varieties of mango. |
| Species diversity | The variety of species in a region | The Western Ghats have greater amphibian species diversity than the Eastern Ghats. |
| Ecological diversity | The variety of ecosystems in a region | India, with deserts, rain forests, mangroves, coral reefs, wetlands, estuaries and alpine meadows, has greater ecosystem diversity than a Scandinavian country like Norway. |
How many species are there?
- According to the IUCN (2004), slightly more than 1.5 million plant and animal species have been described so far.
- Many more are still undescribed, especially in the tropics. The ecologist Robert May estimated the global total at about 7 million species.
- More than 70 per cent of all recorded species are animals. Plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) make up no more than 22 per cent.
- Insects are the most species-rich group: more than 70 per cent of all animal species. About 7 of every 10 animals on Earth are insects.
- There are more species of fungi than of fishes, amphibians, reptiles and mammals put together.
- Counting prokaryotes is hard, because many cannot be grown in the laboratory. Using biochemical or molecular methods, their diversity could run into millions.
India's biodiversity
India has only 2.4 per cent of the world's land area but 8.1 per cent of global species diversity. Your textbook counts it among the 12 megadiversity countries of the world. (Extra reading, not in your textbook: some later lists name 17.) Nearly 45,000 species of plants and twice as many animals have been recorded from India. By May's estimate, only about 22 per cent of all species have been described. Applying this to India, there are probably more than 1,00,000 plant species and more than 3,00,000 animal species still to be discovered.
Indian farmers have bred thousands of rice varieties, from fragrant Basmati to drought-hardy local types, and hundreds of mangoes such as Alphonso, Banganapalli and Langra. This genetic diversity is a store of traits, such as disease resistance, for future crops.
1 marks: “Who popularised the term biodiversity?” Edward Wilson.
2 marks: “India has only 2.4% of the world's land area. What share of global species diversity does it hold, and what does this make India?” About 8.1% of global species diversity. This makes India one of the 12 megadiversity countries of the world.
3 marks: “Explain genetic, species and ecological diversity with one Indian example of each.” Genetic: Rauwolfia vomitoria varies in reserpine across the Himalayas; over 50,000 rice strains. Species: the Western Ghats have more amphibian species than the Eastern Ghats. Ecological: India's many ecosystems, from deserts to coral reefs, exceed Norway's.
Biodiversity is GSE: Genes within a species, Species in a region, Ecosystems across a land.