Dinosaurs, saber toothed tigers and the dodo bird are famous examples of animals that have become extinct. In the case of the dinosaurs, it seems likely that an asteroid strike altered the global climate enough to lead to their disappearance. More recent extinctions and near-extinctions such as the blue whale, tiger, panda and the North American bison-resulted directly from human activity. Many species have become extinct without revealing their potential value. Each one is a storehouse of natural genetic and biochemical resources that cannot be replaced.
Lemurs are found only on the tropical island of Madagascar of the east coast of Africa. Rainforest clearance and hunting have taken their toll and only 30 of their original 45 species survive.Habitat loss is the most important cause of extinction. As land is cleared for farming and urban expansion, habitats such as rainforests and grasslands disappear. In East Africa, few wild animals survive outside the boundaries of national parks and game reserves. In other parts of the world, coastal ecosystems are cleared for development. Some species are more vulnerable to extinction than others. A specialised habitat or diet restricts a species to certain locations or foods, especially if it feeds at the upper level of food chains.
The black rhino was once widespread in central and southern Africa. Since the 1970’s has plunged from as many 30,000 to fewer 3000-a result of poaching for its horn. Rhinoceros horn is used in traditional medicine throughout much of Asia and in ceremonial daggers in Yemen.
Species with low rates of reproduction, such as blue whale, whooping cranes and giant pandas, may not breed fast enough to keep up with any increase in their death rate, or to keep their populations large enough to avoid inbreeding, which weakens the gene pool and eventually leads to extinction. Large species, such as African lions, elephants and grizzly bears, used to be hunted for sport.
The Last Tasmanian Wolf 
The largest marsupial carnivores, Tasmanian wolves in Australia and New Guinea in prehistoric times, but by the 19th century they were found only in Tasmania; competition with the dingo may have eliminated them in Australia.
The last Tasmanian wolf died in captivity in 1936.Animals that prey on livestock or attack humans, such as wolves and some crocodiles are often persecuted. Birds of prey and otters were persecuted because they were believed to attack sport species, such as grouse and salmon and dogs be trained to fight European badgers for "sport". Fortunately, such barbaric practices are now banned, although they have not yet ceased altogether. Alien species such as rabbits, rats, dogs, and cats, brought by humans to new habitats, have led to the disappearance of many native species.
Moths, butterflies and some beetles, used to be highly priced by collectors.
There are more than a million of species of insects. Most animals threatened with extinction are insects or other invertebrates.
In New Zealand, rats that escaped from ships carrying European colonists killed flightless birds. Tourists can also endanger species. Hundreds of people wait on beaches of Malaya for the endangered leather-backed turtle to lay eggs. Their noise and cameras frighten and interfere with egg-laying. Remote areas such as Antarctica and Mount Everest are now regularly visited by tourists who disturb the wildlife.
The Siberian tiger is one of the most endangered species on Earth, as a result of forest clearance and hunting. There are thought to be fewer than 500 tigers left-below the minimum figure for adequate reproduction.As more species become extinct each year, awareness has grown of the importance of preserving wildlife. Ecologists have given a new understanding of the contribution made by most species to the ecosystems in which they live. Other scientists have derived many benefits to humans to be derived from threatened species.
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