Tiêu đề BIODIVERSITY & CONSERVATION.pdf ✅

 Digital www.allendigital.in [ 91 ] 1. Introduction to Biodiversity : Biodiversity is the term popularised by the sociobiologist Edward Wilson to describe the combined diversity at all the levels of biological organisation. The most important of them are– (i) Genetic diversity: A single species might show high diversity at the genetic level over its distributional range. The genetic variation shown by the medicinal plant Rauwolfia vomitoria growing in different Himalayan ranges might be in terms of the potency and concentration of the active chemical (reserpine) that the plant produces. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango. (ii) Species diversity: The diversity at the species level. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats. (iii) Ecological diversity: At the ecosystem level, India, for instance, with its deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows has a greater ecosystem diversity than a Scandinavian country like Norway. Biodiversity and Conservation 03 Edward Wilson 1000 varieties of Mango More than 50000 different Strains of Rice Western ghat Eastern ghat
NEET : Biology [ 92 ] www.allendigital.in  Digital (A) How Many Species are there on Earth and How Many in India : 1. According to the IUCN (2004), the total number of plant and animal species described so far is slightly more than 1.5 million, but a more conservative and scientifically sound estimate made by Robert May places the global species diversity at about 7 million. 2. More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22 per cent of the total. Among animals, insects are the most species-rich 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. Again, how do we explain this enormous diversification of insects? The number of fungi species in the world is more than the combined total of the species of fishes, amphibians, reptiles and mammals. In following figure biodiversity is depicted showing species number of major taxa. 3. Although India has only 2.4 per cent of the world's land area, its share of the global species diversity is an impressive 8.1 per cent. That is what makes India one of the 12 mega diversity countries of the world. Nearly 45,000 species of plants and twice as many of animals have been recorded from India. How many living species are actually there waiting to be discovered and named? If we accept May's global estimates, only 22 per cent of the total species have been recorded so far. Vertebrates Invertebrates Plants Representing global biodiversity: Proportionate number of species of major taxa of plants, invertebrates and vertebrates 70 Lakh 5,67,000 species may be in India 8.1% of global biodiversity But discovered 45,000 plants  90,000 animals Total 135000 sp. So, in India yet to be discovered number of Species:567000 –135000 = 432000 (approx.)
Biodiversity and Conservation  Digital www.allendigital.in [ 93 ] It should be noted that these estimates do not give any figures for prokaryotes. Biologists are not sure about how many prokaryotic species there might be. The problem is that – (1) conventional taxonomic methods are not suitable for identifying microbial species and many species are simply not culturable under laboratory conditions. (2) If we accept biochemical or molecular criteria for delineating species for this group, then their diversity alone might run into millions. 1. Type of Biodiversity is/are - (1) Genetic diversity (2) Species diversity (3) Ecological diversity (4) All of these 2. Active chemical in Rauwolfia vomitoria - (1) Terpene (2) Reserpine (3) caffeine (4) None of the above 3. The_________ Ghats have a greater amphibian species diversity than the __________ Ghats. (1) Eastern, Western (2) Western, Eastern (3) Western, Southern (4) Eastern, Southern 4. IUCN stands for________ (1) International union for conservation of Natural resources (2) Indian union for conservation of Nature (3) Italian Union for conservation at Nature (4) International Union for conservation of Nature and Natural Resources 5. India has only _________ present at the world’s land area. Its share of the global species diversity in an impressive _________ Present. (1) 2.4, 8.1 (2) 8.1, 2.4 (3) 4.1, 8.2 (4) 8.4, 2.1 6. How many species of birds found in India? (1) 1500 (2) 1400 (3) 1200 (4) 1700 (B) Patterns of Biodiversity : (i) Latitudinal gradients : The diversity of plants and animals is not uniform throughout the world but shows a rather uneven distribution.In general, species diversity decreases as we move away from the equator towards the poles. With very few exceptions, tropics (latitudinal range of 23.5° N to 23.5° S) harbour more species than temperate or polar areas. Colombia located near the equator has nearly 1,400 species of birds while New York at 41° N has 105 species and Greenland at 71° N only 56 species. India, with much of its land area in the tropical latitudes, has more than 1,200 species of birds. A forest in a tropical region like Ecuador has up to 10 times as many species of vascular plants as a forest of equal area in a temperate region like the Midwest of the USA. The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth - it is home to more than 40000 species of plants, 3000 of fishes, 1300 of birds, 427 of mammals, 427 of amphibians, 378 of reptiles and more than 125000 invertebrates. BEGINNER’S BOX-1 INTRODUCTION TO BIODIVERISITY
NEET : Biology [ 94 ] www.allendigital.in  Digital (ii) Species-Area relationships: German naturalist and geographer Alexander von Humboldt observed that within a region species richness increased with increasing explored area, but only up to a limit. log S = log C + Z log A where S= Species richness A= Area Z = slope of the line (regression coefficient) C = Y-intercept Ecologists have discovered for a small region (Britain, California, New York) the value of Z lies in the range of 0.1 to 0.2, regardless of the taxonomic group. For very large areas like the entire continents the value of Z lies in the range of 0.6 to 1.2. In the tropical forests of different continents for frugivorous (fruit-eating) birds and mammals value of Z found to be 1.15. The steeper slopes in this context means more species richness. (C) The Importance of Species Diversity to the Ecosystem : • For many decades, ecologists believed that communities with more species, generally, tend to be more stable than those with less species. What exactly is stability for a biological community? 1. A stable community should not show too much variation in productivity from year to year; 2. it must be either resistant or resilient to occasional disturbances (natural or man-made), 3. It must also be resistant to invasions by alien species. • We don’t know how these attributes are linked to species richness in a community, but David Tilman’s long-term ecosystem experiments using outdoor plots provide some tentative answers. Tilman found that plots with more species showed less year-to-year variation in total biomass. He also showed that in his experiments, increased diversity contributed to higher productivity. • Although, we may not understand completely how species richness contributes to the well-being of an ecosystem, we know enough to realise that rich biodiversity is not only essential for ecosystem health but imperative for the very survival of the human race on this planet. • There are no direct answers to such naive questions but we can develop a proper perspective through an analogy (the ‘rivet popper hypothesis’) used by Stanford ecologist Paul Ehrlich. In an airplane (ecosystem) all parts are joined together using thousands of rivets (species). If every passenger travelling in it starts popping a rivet to take home (causing a species to become extinct), it may not affect flight safety (proper functioning of the ecosystem) initially, but as more and more rivets are removed, the plane becomes dangerously weak over a period of time. Furthermore, which rivet is removed may also be critical. Loss of rivets on the wings (key species that drive major ecosystem functions) is obviously a more serious threat to flight safety than loss of a few rivets on the seats or windows inside the plane. (D) Causes of Biodiversity Losses : The accelerated rates of species extinctions that the world is facing now are largely due to human activities. There are four major causes (‘The Evil Quartet’ is the sobriquet used to describe them). Log S = log C + Z log A S=CAZ Area Showing species area relationship Species richness