It is the term biodiversity refers to the totality of genes, species, and ecosystems of a region.
· Types of biodiversity described by Edward Wilson:
o Genetic diversity: A single species might show high diversity at the genetic level over its distributional range.
§ Medicinal plant Rauwolfia vomitoria of Himalayan range produces active chemical reserpine shows genetic variation.
§ India has more than 50000 different strain of rice.
§ 1000 varieties of mango.
· Species diversity: different species of a single animal like frog.
· Ecological diversity: diversity in the ecosystem level like desert, rain forest, mangroves, coral reef, wetlands, estuaries etc.
How many species are there on Earth and How many in India?
· According to IUCN (2004), 1.5 million of plants and animals are in our biosphere.
· Robert May places global species diversity at about 7 millions.
· More than 70 percent of all the species recorded are animals.
· All plants constitute about 22 percent.
· Among animals insects constitute 70 percent.
· India has only 2.4 percent of the world’s land area; its share of global species diversity is impressive 8.1 percent.
· India is considered one of the mega diversity countries of the world.
Pattern of Biodiversity:
· Species diversity decreases as we move away from the equator towards the pole.
· Tropic (23.5o N to 23.5o S) harbors more species than temperate and pole
· The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth:
· 40,000 species of plants.
· 3000 species of fishes.
· 1300 of birds.
· 427 amphibians
· 378 reptiles
· More than 1, 25,000 invertebrates.
Why tropical rain forest has greater biodiversity:
· Unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
· Tropical environments. Unlike temperate ones, are less seasonal, relatively more constant and predictable, promotes niche specialization and lead to greater species diversity.
· There is more solar energy available in the tropics, which contribute to higher productivity.
Species area relationship:
· ALEXANDER VON HUMBOLDT observed within a region species richness increased with increasing explored area but only up to a limit.
· The relation between species richness and area for a wide variety of taxa turns out to be a rectangular hyperbola.
· On a logarithmic scale the relationship is a straight line describe by the equation LogS = logC +Z log A
Where S= species richness, A = Area, Z = slope of the line (regression coefficient), C = Y- intercept.
· It has been noted that regardless of the taxonomic group or region the slope of the regression line are amazingly similar. However, for a very large area like the entire continent the slope of the line is steeper.
Importance of species diversity to the Ecosystem:
· Community with more species generally tends to be more stable than those with less species.
· A stable community should not show too much variation in productivity from year to year; it must be resistant or resilient to occasional disturbances (natural or man-made)
· Stable community must be resistant to invasion by alien species.
· David Tillman’s long-term field experiment finds that:
o Plots with more species showed less year to year variation in biomass
o Increased diversity contributed to higher productivity.
· The rivet popper hypothesis:
o In an airplane (ecosystem) all parts are joined together by thousands of rivets (species).
o If every passenger starts popping a rivet to take home (species extinct), it may not affect flight safety initially but as more and more rivets are removed the plane becomes dangerously weak.
o Furthermore which rivet is removed may also be critical.
o Loss of rivets on the wings (key species) is obviously a more serious threat to flight safety than loss of a few rivets on the seats or windows inside the plane.
Loss of Biodiversity:
· The IUCN Red List (2004) documents the extinction of 784 species.
· Recent extinction includes:
o Dodo (Mauritius).
o Quake (Africa)
o Thylacine (Australia)
o Stiller’s cow (Russia)
o Three subspecies of tiger (Bali, Java, Caspian).
· Since the origin and diversification of life on earth there were five episodes of mass extinction of species.
· The sixth mass Extinctions in progress now.
How the’ sixth Extinction’ is different from the previous five extinctions.
· The current extinction rate is 100 to 1000 times faster.
· All others are pre-human period, this one is anthropogenic.
Effect of biodiversity loss:
Causes of biodiversity loss:
Habitat loss and fragmentation:
Alien species invasion:
In insitu conservation threatened organisms are protected in their own locality while in exsitu conservation they are carried away from their natural habitat.