CLASSROOM World's biodiversity needs to be preserved Biodiversity - the billions of life forms that exist on earth - ranges in size from microscopic viruses to blue whales that are more than 30 metres long. Conserving biodiversity could be humankind's greatest challenge. IAGHAVENDRA GADAGKAR THE MOST reliable guess that scientists have ventured about the origin of the universe is that it was the result of a cosmic explosion that took place about 25 billion years ago. Before the explosion, all matter in the universe is believed to have existed as a highly condensed cosmic egg. The so-called "big bang", say scientists, sent the matter from the cosmic egg hurtling into the universe to form a countless number of stars. Several stars form a galaxy. And galaxies are clustered into groups. Our own cluster, consisting of about 25 _galaxies, is called the local group and one of its galaxies is known as the Milky Way, which consists of over a hundred billion stars. The sun is one of the stars in the Milky Way and it has nine planets revolving around it, the third of which in distance from the sun is the earth. As far as is known, the earth is the only planef to possess that remarkable entity called life. The earth was bitirn about 4.6 billion years ago. A primitive form of life is thought to have originated on earth through complex chemical reactions about 3.6 bil- lion years ago. These living entities, being capable of dividing and changing, set off a chain of events that is referred to as biological evolution. For nearly 3 billion of the 3.6 billion years, life existed as microscopic blobs of protoplasm in the ocean. But about 600 m years ago, these living organisms became larger and more diverse I and, in time, developed hard skeletal structures: .., forms of life led it to neglect the state of the planet on which it lived. Fortunately, the same mental qualities that enabled human beings to explore space and land on the moon, also enable them to reflect on their past, their present and their future. Perhaps, it is this quality that will prove humankind's ultimate saviour. Over the past 25 years or so, there has been a rather sudden realisation that human beings have damaged their planet beyond recognition and perhaps beyond repair. They have destroyed the earth's life-support sys- tems, which evolved over billions of years, and burnt fos- Total animal biomass Figure: 1 Other soil fauna Ants and termites Reptiles Amphibia Major developments in this drama were the evolution ..__ ____________ about 400 m years ago of plants and animals, which could live on land instead of water. Insects and reptiles arrived about 300 m years ago, birds and mammals about 200 m years ago and flowering plants about 50 m years later. Evolution of Homo sapiens This gradual and relatively smooth evolution to progres- sively more complex forms of life received a major jolt about 2 m years ago with the origin of a rather special lineage of primates referred to as the genus Homo. A sin- gle species of this line evolved about 40,000 years ago into Homo sapiens, displaying all the qualities of pre- sent-day human beings. Homo sapiens' qualities of intel- ligence and ability to manipulate the environment enabled the species to gain unprecedented mastery over other forms of life. Indeed, Homo sapiens manipulated their physical environment to the extent that for the first time a species of living organism cut loose from the constraints of bio- logical evolution and produced 5 billion individuals. Unfortunately, humankind's euphoria over its mas- tery of the universe, its ability to increase its own life expectancy and its ability to genetically engineer other sil fuels and decimated forests on such a large scale that temperatures on earth have' increased perceptibly. The chilling realisation that the earth cannot support humankind's bid to grow food; provide shelter and pro- duce consumer goods for a population whose numbers and demands are increasing is beginning to dawn on a reasonable number of people. Yet many are still unaware that every day they are destroying, perhaps by the dozens, fellow living creatures, which have evolved like them. This magnificent range of life is known by the term biodiversity, which has only recently become fashion- able and part of the vocabulary of politicians and admin- istrators. But few are aware that even scientists know lit- tle about this biodiversity that human beifigs now want to save. Five kingdoms What is biodiversity? It is commonly known that the earth abounds in a spectacular range of living organisms. They are customarily classified into five "kingdoms", of which the first is protistra (bacteria and blue-green algae); the second, monera (advanced algae); third, fungi; 43 DOWIUO WTH VOL 1 NO 11 OCTOBER 31, 1992