Extinction is the state of being extinct, that is when an entire species down to the last individual ceases to exist. A species is called functionally extinct when individuals of a species do exist but are unable to reproduce. Extinction is a natural and normal process, and is a tool in the cycle of evolution. Speciation gives rise to new species that occupy and make a niché for themselves within nature. Older species that cannot cope with changing conditions or with fitter organisms go onto become extinct. Most species have a shelf life of about 10 million years after their first appearance. Today, only about one in 1,000 species that have existed remain.
Prior to human civilization, extinction was a very slow process across the planet; in fact, mass extinctions were extremely rare. Human beings and their way of living have amplified mass extinctions to an unprecedented rate. Biologist E.O. Wilson, in his book The Future of Life, has predicted that within the next 100 years more than half of the planet's species will be extinct.
In many cases species turn extinct only in the wild. With continued human efforts of conservation, critically endangered species are preserved within zoos or artificial environments. Such efforts give rise to the chance of future reintroduction of the species in to the wild. The danger of extinction of a certain species in the wild population is that it causes a chain of extinction within other dependant species.
 Reasons for Extinction
Each species has its own unique set of causes behind its extinction, some causes specific and complex, while some reasons are rather blatant and obvious. Most commonly, any species that finds it difficult to cope with its environment dies out and goes extinct. More recently, strong and healthy species are getting wiped out completely for reasons varying from toxic pollution to habitat degradation or human encroachment. Naturally extinction is meant to occur over thousands or millions of years, where species invariably lose to better, fitter and more equipped species.
 Mass Extinctions
Since the creation of earth, scientists know of at least five mass extinctions and four in the previous 3.5 billion years. The last of these mass extinctions was said have been the K-T extinction, which concluded 65 million years ago at the end of the Cretaceous Age. This mass extinction is said to have brought an end to all non-avian dinosaurs and numerous other species. A large group in the scientific community believes that the planet's species are going through another new phase of human-caused mass extinction, called the Holocene Extinction event.
 Human Interest in Extinction
Extinction has become one of the hottest fields of research among the sciences of zoology and biology. In fact, it is now a major area of concern with billions of dollars worth of funds being pumped in towards conservation. Organisations, such as the Worldwide Fund for Nature and the International Fund for Animal Welfare, were created with the sole purpose of preserving species from extinction. Numerous governments have also passed laws to prevent extinction and to avoid human-caused extinctions.
 References and Useful Websites
- A Dictionary in Plain English, published By Images Asia