Extinction occurs when a particular species completely disappears from the planet. Extinction has been going on since life began on Earth, but today, it is happening faster than ever before.
Species disappear because of changes that are caused either by nature or by the actions of people. Sometimes a terrible natural event, like a volcano erupting, can kill an entire species. Other times, extinction will happen slowly as nature changes the world. For example, after the Ice Ages, when the glaciers melted and Earth became warmer, many species died because they could not live in a warmer climate. Newer species that could survive a warmer environment took their places. Current practices that contribute to extinction are habit destruction, pollution, invasive species, moving species from the wild into captivity and many others. (Source: EPA / Photo: Flickr)