Pathogens resistant to drugs a major contender for

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6. Pathogens resistant to drugs . A major contender for the key problem of the 21 st century (others covered later in this course). For example, bacteria mutate to new, resistant forms. Garrett The Coming Plague . Experiment on E. coli shows this. Slide Bred for resistance to antibiotic and this occurs gradually over time. Would need to change drugs if this occurred clinically. A tradeoff: resistant ones poorer in competition under natural (drug-free) conditions. A very important current example is Methicillin-resistant Staphylococcus aureus ( MRSA) , which often infects people in hospitals. You probably all know people who have had this disease. 7 . Pest resistance to pesticides . Mosquitoes and crop- damaging insects acquire resistance to DDT etc. First use of DDT was in Italy in 1943 for typhus lice. Already by 1951 many insects such as mosquitoes were resistant. Malaria is a major re-emerging problem because of resistance of mosquito carriers to DDT and resistance of the pathogen (a sporozoan) to chloroquine drugs. In 1975, world-wide incidence of malaria was 2.5x that in 1961, now leveling off but not declining. Each year 350-500 million cases and c2 million deaths. The biologist W.D. Hamilton (inventor of kin selection, Topic 4) died of complications from malaria in Africa (c90% of world cases there). Those never exposed at huge risk. Cases have been mostly tropical, but some dozens in US since 1950, most in CA.
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Conclusion : Many examples of natural selection are associated with major changes in environment by humans (not all). The mechanism of evolution by natural selection can produce all these phenomena – humans speed things up. These are examples of natural selection as observed over short periods of time – “evolution in action.” Natural selection is probably more important now than at any time in the history of the earth.
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