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Mass Extinction2 - development of social and language...

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Mass Extinctions Extinctions occur when environments change too fast. Local extinctions can occur, as can mass extinctions: they differ in scale, scope and the numbers of species involved. There have been five environmental changes (mostly cooling) of global proportions that resulted in the five mass extinctions in Earth history. Recovery from these extinctions took millions of years. A spectacular exception was the large meteorite strike sixty-six million years ago near the Yucatán peninsula in Mexico that either caused the extinction of dinosaurs and 75% of all marine species, or was the nail in the coffin of the dinosaurs. There have been several natural mass extinctions in the history of earth followed by recovery. Human activities that reduce biodiversity began about 30,000 years ago with
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Unformatted text preview: development of social and language skills to apply increasingly better stone tool technology to trap and kill the largher animals. Hunting contributes to the estimated extinction of 15,000 to 30,000 species a year. Fish stocks are being depleted by overfishing. Commercial trade causes exploitation of tigers, cheetahs, leopards, jaguars, etc. for furs; sharks for fins; rhinoceros for rhino horn powder; elephants for tusks for ivory; and cacti for gardeners. A major cause of extinction is the loss of habitat to support a species. The habitat for a species may be totally destroyed through natural events or human activities. Habitats may be fragmented into small pieces that cannot support the population. By 2010, very little undisturbed rain forest will exist outside of national parks....
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