Biology SPECIES DIVERSITY

### KEY TOPICS

star Species Diversity on Earth
star Species Richness in Different Taxa
star Species Diversity in India

### SPECIES DIVERSITY ON EARTH

● Since there are published records of all the species discovered and named, we know how many species in all have been recorded so far, but it is color{violet}("not easy to answer the question") of how many species there are on color{violet}("earth.")

● According to the color{violet}("IUCN (2004)"), the total number of color{violet}("plant") and color{violet}("animal") species described so far is slightly more than 1.5 million, but we have no clear idea of how many species are yet to be color{violet}("discovered") and color{violet}("described.")

● Estimates vary widely and many of them are only color{violet}("educated guesses.")

● For many color{violet}("taxonomic") groups, species inventories are more complete in temperate than in color{violet}("tropical countries.")

● Considering that an overwhelmingly large proportion of the species waiting to be discovered are in the color{violet}("tropics, biologists") make a statistical comparison of the color{violet}("temperate-tropical") species richness of an exhaustively studied group of insects and extrapolate this color{violet}("ratio") to other groups of color{violet}("animals") and color{violet}("plants") to come up with a gross estimate of the color{violet}("total number") of species on color{violet}("earth.")

● Some extreme estimates range from 20 to 50 million, but a more color{violet}("conservative") and color{violet}("scientifically sound") estimate made by color{violet}("Robert") May places the global species diversity at about 7 million.

● Let us look at some interesting aspects about color{violet}("earth’s biodiversity") based on the currently available species inventories.

### SPECIES RICHNESS IN DIFFERENT TAXA

● More than 70 per cent of all the species recorded are color{violet}("animals"), while color{violet}("plants (including algae, fungi, bryophytes, gymnosperms") and color{violet}("angiosperms") ) comprise no more than 22 per cent of the total.

● Among color{violet}("animals"), insects are the most species-rich color{violet}("taxonomic") group, making up more than 70 per cent of the total.

● That means, out of every 10 animals on this planet, 7 are insects.

● The number of color{violet}("fungi") species in the world is more than the color{violet}("combined total") of the species of color{violet}("fishes, amphibians, reptiles") and color{violet}("mammals.")

● color{violet}("Biodiversity") is depicted showing species number of color{violet}("major taxa.")

● It should be noted that these estimates do not give any figures for color{violet}("prokaryotes.")

● color{violet}("Biologists") are not sure about how many color{violet}("prokaryotic") species there might be.

● The problem is that color{violet}("conventional taxonomic methods") are not suitable for color{violet}("identifying microbial species") and many species are simply not culturable under color{violet}("laboratory conditions.")

● If we accept color{violet}("biochemical") or color{violet}("molecular criteria") for delineating species for this group, then their color{violet}("diversity") alone might run into millions.

### SPECIES DIVERSITY IN INDIA

● Although India has only color{violet}("2.4 per cent") of the color{violet}("world’s land area"), its share of the color{violet}("global species diversity") is an impressive 8.1 per cent.

● That is what makes our country one of the color{violet}("12 mega diversity") countries of the world.

● Nearly color{violet}("45,000 species") of color{violet}("plants") and twice as many of color{violet}("animals") have been recorded from India.

● If we accept May’s global estimates, only color{violet}("22 per cent") of the total species have been recorded so far.

● Applying this proportion to India’s color{violet}("diversity figures"), we estimate that there are probably more than color{violet}("1,00,000 plant") species and more than color{violet}("3,00, 000 animal") species yet to be color{violet}("discovered") and color{violet}("described.")

● Questions like would the inventory of the color{violet}("biological wealth") of our country ever be completed and regarding the immense trained manpower (taxonomists) and the time required to complete the job color{violet}("plague the ecologists.")

● The situation appears more hopeless when we realise that a color{violet}("large fraction") of these species faces the threat of becoming extinct even before we color{violet}("discover") them.

● color{violet}("Nature’s biological library") is burning even before we catalogued the titles of all the books stocked there.