Species is a group of organisms belong to the same biological species. An extinct species is one that is no longer living. The earth's species are dying out, up to 1000 times faster than their natural rate of extinction. Every day 137 species disappear from the earth, which means 50,000 species are dying each year. Many factors like natural disasters affect the ecosystem and species become extinct for a number of reasons but the primary cause is the destruction of habitat by human activities. First of all, as species evolve, most adapt to a specific environment that best meets their survival needs.Without this habitat the species may not survive. Pollution, drainage of wetlands,conversion of shrub lands to grazing lands, cutting and clearing of forests, urbanization, coral-reef destruction, and road and dam construction have destroyed and seriously damaged and fragmented habitats. Habitat loss and fragmentation is the most pervasive threat to birds, mammals and amphibian.
It is affecting 86% of all threatened birds, 86% of the threatened mammals and 88% of amphibians. This reduces their bio-diversity and makes them less adaptable to environmental change.
Secondly, Pollution is another important cause of extinction. Toxic chemicals, for example chlorinated hydrocarbons, DDT and PCB's have become concentrated in food webs and food chains that circulate energy through an ecosystem. These toxic chemicals strongly affect species. DDT and PCBs cause the eggs of species and destroy the malformed eggs. Water pollutions and increased water temperatures have wiped out species of fish in many habitats. Oil spills destroy birds, fish, and mammals and may pollute the oceans floors. Acid rains is the result of extreme air pollution, kills organisms in freshwater lakes and destroy large tracts of forested land.