Natural Selection Image Map


Human-driven Extinction

  Why should humans worry about species extinction and the disruption of ecosystems?  When our actions cause a population to become extinct we lose valuable knowledge, and in some cases, even potential aides to humankind.  For instance, many medicines are discovered in plants. What happens if these plant species become extinct before scientists discover that they contain useful chemicals?  Also, with every extinction, many food chains lose valuable links, upsetting the ecological balance.

For these reasons, the U.S. Fish and Wildlife Service Endangered Species Program was created by the Endangered Species Act of 1973. 

Bioinvaders

What do airplanes, trains, automobiles, boats, telephones, and the internet have in common?  Can we say that they keep us connected to each other?  In nature, many ecosystems, like islands, are isolated from outside influences. Can humans affect that isolation?  Human commercial and recreational activities can introduce new populations that are likely to disturb the existing balance.

For example, in Hawaii, the Jackson’s chameleon, native to East Africa, was introduced a few decades ago.  Today, this invasive species continues to expand its population to all the Hawaiian islands.  Since a large part of the chameleon's diet consists of small insects, other species that normally feed on insects (small birds, for example), have begun to decrease in number.  Trying to maintain a balance between natural populations and invasive species, like the Jackson’s chameleon, costs the United States over 100 billion dollars per year.
One change in bacterial populations is taking place now. The widespread use of antibiotics is leading to the evolution of new strains of bacteria that are resistant to antibiotics. In any infection, there may be a few bacteria that are naturally resistant to the antibiotic being used to treat it.  If these survivors are not killed off by the body's own defenses, they can proliferate and continue the infection. Have you ever had a bad cold or infection where the doctor prescribed antibiotics.  Do you remember being told not to skip any doses and to take all the doses for a full 5 days or so?  Why do you suppose these instructions were given. 

                                                                            

 

 

 

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