Lesson 12 of 12 · 12 min
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Must-know facts
20 facts
- 1Edward Wilson popularised the term biodiversity; its three key levels are genetic, species and ecological.
- 2Genetic diversity: Rauwolfia vomitoria (reserpine) across the Himalaya; India's 50,000+ rice strains and 1,000 mango varieties.
- 3Species diversity: Western Ghats have more amphibian species than the Eastern Ghats. Ecological: India more than Norway.
- 4IUCN (2004): slightly more than 1.5 million species described; Robert May's estimate about 7 million; extreme estimates 20-50 million.
- 5Recorded species: animals more than 70 per cent, plants no more than 22 per cent; insects more than 70 per cent of animals.
- 6Fungi outnumber fishes, amphibians, reptiles and mammals combined in species.
- 7India: 2.4 per cent of world land, 8.1 per cent of species; one of 12 mega diversity countries; about 45,000 plant species and twice as many animal species.
- 8Birds: Colombia nearly 1,400, New York (41° N) 105, Greenland (71° N) 56, India more than 1,200.
- 9Tropics are richer: more evolutionary time, a constant environment, more solar energy.
- 10log S = log C + Z log A; Z is 0.1-0.2 within regions, 0.6-1.2 for continents, 1.15 for frugivorous birds and mammals.
- 11Tilman: more species, less year-to-year variation in biomass and higher productivity.
- 12Rivet popper hypothesis: Paul Ehrlich; wing rivets are key species.
- 13IUCN Red List (2004): 784 extinctions in 500 years (338 vertebrates, 359 invertebrates, 87 plants); 27 species lost in the last twenty years.
- 14More than 15,500 species threatened: 12 per cent birds, 23 per cent mammals, 32 per cent amphibians, 31 per cent gymnosperms.
- 15The Sixth Extinction is 100 to 1,000 times faster than pre-human rates.
- 16Evil quartet: habitat loss and fragmentation (most important), over-exploitation, alien species invasions, co-extinctions.
- 17Nile perch in Lake Victoria: more than 200 cichlid species extinct.
- 1834 hotspots, three covering India: Western Ghats and Sri Lanka, Indo-Burma, Himalaya.
- 19India: 14 biosphere reserves, 90 national parks, 448 wildlife sanctuaries.
- 20Ex situ: zoos, botanical gardens, safari parks, cryopreservation, in vitro fertilisation, tissue culture, seed banks. Earth Summit Rio 1992; Johannesburg 2002 with 190 countries.
Common traps
Where marks are lost
Giving Z = 0.6-1.2 for small regions.
Within a region Z is 0.1-0.2; only very large areas such as whole continents give the steeper 0.6-1.2.
Naming over-exploitation as the most important cause of extinction.
Habitat loss and fragmentation is the most important of the evil quartet.
Calling a sacred grove ex situ conservation.
A sacred grove protects the forest where it stands, so it is in situ; zoos, seed banks and cryopreservation are ex situ.
Saying plants make up most recorded species.
Animals are more than 70 per cent of recorded species and plants no more than 22 per cent.
Writing that India holds 8.1 per cent of the world's land.
India has 2.4 per cent of the land and 8.1 per cent of the species.
Listing four hotspots in India or naming the Eastern Ghats.
Three: Western Ghats and Sri Lanka, Indo-Burma, and Himalaya.
Thinking the species-area curve is a straight line on ordinary axes.
It is a rectangular hyperbola; it becomes straight only on logarithmic scales.
Saying the current extinction rate equals past mass extinctions.
It is 100 to 1,000 times faster than pre-human rates, driven by humans.
Key terms
18 terms
- Biodiversity
- The combined variety of life at every level of biological organisation, from genes to biomes.
- Genetic diversity
- Variation within one species across its range, as in the reserpine content of Rauwolfia vomitoria.
- Species diversity
- The variety of species in a region, such as amphibians in the Western Ghats.
- Ecological diversity
- The variety of ecosystems in a region, such as India's deserts, forests, mangroves and reefs.
- Mega diversity country
- One of the 12 countries holding an exceptionally large share of the world's species; India is one.
- Latitudinal gradient
- The fall in species diversity from the equator towards the poles.
- Species-area relationship
- Species richness rises with area to a limit; log S = log C + Z log A.
- Z (regression coefficient)
- Slope of the log S against log A line; 0.1-0.2 within regions, 0.6-1.2 for continents.
- Rivet popper hypothesis
- Paul Ehrlich's analogy of species as rivets holding an airplane (the ecosystem) together.
- Evil quartet
- The four main causes of biodiversity loss: habitat loss and fragmentation, over-exploitation, alien invasions, co-extinctions.
- Co-extinction
- Extinction of species tied obligatorily to one that has gone extinct.
- Bioprospecting
- Exploring molecular, genetic and species diversity for products of economic importance.
- Endemism
- Species being confined to one region and found nowhere else.
- Biodiversity hotspot
- A region of very high species richness and endemism, chosen for maximum protection; there are 34.
- In situ conservation
- Protecting species in their natural habitat by protecting the whole ecosystem.
- Ex situ conservation
- Protecting threatened species away from their habitat, in zoos, gardens, seed banks or by cryopreservation.
- Sacred grove
- A forest tract protected by religious and cultural tradition, with all its trees and wildlife.
- Cryopreservation
- Keeping gametes viable and fertile for long periods at very low temperature.