Dinosaur and Extinction

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Extinction is the termination of evolutionary lineage. The most common extinction event is the loss of a species. There are many reasons why a species might die out. Human intervention (either directly or indirectly) has become the leading cause of species extinction (possibly for the last fifteen thousand years).

Species and Populations

An important distinction must be made between true extinction and extirpation. Extirpation is the loss of a population, or loss of a species from a particular geographic region. A famous twentieth-century example is the extirpation of wolves from the Yellowstone region of Wyoming. The park service reintroduced wolves to Yellowstone in the 1990s, and these predators appear to be adapting well to their new home. True extinction must also be differentiated from pseudoextinction. Biologists studying the changes that take place in a lineage over time often designate distinct morphological stages as separate species. The extinction of a species in this context is not the result of the termination of a lineage, but rather the transformation into a new form.

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The giant panda actually has a carnivorous digestive system, so it must eat voraciously for 10 to 12 hours to consume enough bamboo (up to 66 pounds [30 kilograms]) each day.

A clear understanding of the definition of a species is necessary in order to discuss extinction. This is not a simple question, but one view defines a species as a population of potentially interbreeding individuals that is reproductively isolated from other such populations. By this definition the relatively common mating between coyotes and domestic dogs raises the question of the validity of their separate species status.

Environmental Change

Species go extinct primarily because they are unable to adapt to a changing environment. Animals with specialized food or habitat requirements, such as the giant panda (which feeds almost...
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