Lecture 38-Agriculture and Selection

Lecture 38-Agriculture and Selection - Lecture 38-...

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Lecture 38- Agriculture: Putting Selection to Work Bacteria -Prokaryotes; reproduce every 20 minutes -t=0 hours: 1 cell; t=10 hours: 1,048576 cells Antibiotic Resistance -Antibiotics are produced by microbes; inhibit the growth of cells. Antibiotic resistance can arise from mutation; resistance is inherited -Resistance can spread from species to species. Antibiotic resistance is a serious problem. -Humans provide “selective forces”; i.e. we kill some bacteria but leave the resistant ones, which replicate to produce a resistant strain of bacteria -Humans and other animals are adversely affected Consequences*** Question: Assume a population of 10 million disease-causing bacteria are making you unwell. a) Apply an antibiotic that kills 99% of them. If the bacteria left alive after treatment are resistant, and if generation time is 20 min, how long will it take the population to return to 10 million? b) What if the antibiotic kills 99.99% of them? -Figure it out. Expect this on the exam. Selection is an Agent for Change -Factors such as pattern of reproduction (sexual, asexual), generation time, and size of a population affects the potential of a population to rebound -Inherited advantage is the basis on which selection works. E.g., antibiotic resistance, resistance to DDT Syphilis ( Treponema pallidum) -Caused by a bacteria -Appeared in Europe in 1945, killed millions. New World version called Yaws (only transmitted by skin-skin contact) -Disease moved from foot to skin, created a new niche Evolution of Whales -Aquatic animal (which can be determined by bone density) -Mammals moved into a new adaptive zone to avoid predators, and made adaptive changes to live underwater Impact of Selection and Partial Treatment -Measles outbreaks in the Sahel region of Africa (Niger) also illustrate the impact of selection and partial treatment -Related to rainfall; disease comes back if everyone is not
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This note was uploaded on 04/04/2009 for the course BIOLOGY 1222 taught by Professor Haffie during the Spring '09 term at UWO.

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Lecture 38-Agriculture and Selection - Lecture 38-...

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