Read the following passage and answer the following questions:

During the past few centuries, with the increase in human population, biodiversity has come under tremendous pressure. Biological extinction, which led to the disappearance of one species in several hundred years, has now been replaced by an accelerated rate of extinction-one species every year. This is the result of the extensive habitat changes brought by mankind. If the same pace continues, an estimated one-fourth to one-third of species is likely to become extinct within the next few decades. Over all, roughly 1000 birds and mammals are now thought to be in jeopardy. Although endangered animals, e.g. tigers in Asia, cheetahs in Africa, whales in the Antarctic, whooping cranes in North America, etc., receive great public attention, plant extinctions are often more significant ecologically. According to Peter H. Raven, Director of the Missouri Botanical Garden, a disappearing plant can take with it ten to thirty dependent species such as insects, higher animals, and even other plants. The International Union for Conversation of Nature and Natural Resources (IUCN) finds about 10 per cent of the world's flowering plants to be dangerously rare or under threat.

These estimates of species at risk understate the true problem', for they deal only with known and higher life forms. It seems probable that many unnamed species are disappearing in scientifically uncharted tropical areas. In his book The Sinking Ark, Norman Myers surmises on the basis of exploitation that, right now, at least one species might be disappearing each day in tropical forests alone. Even outside the tropics, many small, obscure organisms such as worms, mites, beetles and herbs may be disappearing, without our knowledge. Besides, an examination of the survival prospects of all forms of plant and animal life- including obscure, fens, shrubs, insects, mollusks, elephants and wolves indicates that huge number of them have little future. Loss of such a multitude of species would constitute an irreversible alternation in the nature of the biosphere even before we understand its workings an evolutionary Rubicon whose crossing Homo sapiens would do well

1)A)Why has the natural environment suddenly come under great pressure? Give example from the passage to show the pressure.