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Evolution in Everyday Life

Evolution in Everyday Life. The evolution of pesticide resistance in insects. The evolution of herbicide resistance in weeds. The evolution of antibiotic resistance in bacteria. The evolution of drug resistance in viruses. Charles Lyell was A contemporary of Darwin. A dynamical geologist.

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Evolution in Everyday Life

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  1. Evolution in Everyday Life • The evolution of pesticide resistance in insects. • The evolution of herbicide resistance in weeds. • The evolution of antibiotic resistance in bacteria. • The evolution of drug resistance in viruses.

  2. Charles Lyell was • A contemporary of Darwin. • A dynamical geologist. • An important influence on Darwin’s thinking about how to study biology. • The captain of the Beagle on Darwin’s voyage. • All of the above except (D).

  3. The concept that a weak force over a long period of time can have an effect comparable to that of a stronger force in a much shorter period of time is called: • Gradualism. • Adaptation. • Uniformitarianism. • Superposition. • Transmutation.

  4. Referring to the Figure above, rank the species pairs (1,2), (2,3), (3,4) from least similar to most similar according to Darwin: A) (1,2) least < (2,3) < (3,4) most. B) (2,3) least < (3,4) < (1,2) most. C) (1,2) least < (3,4) < (2,3) most. D) (3,4) least < (1,2) < (2,3) most. E) (3,4) least < (2,3) < (1,2) most.

  5. Dots are Most Recent Common Ancestors (1,2) (2,3) (3,4) Referring to the Figure above, rank the species pairs (1,2), (2,3), (3,4) from least similar to most similar according to Darwin: A) (1,2) < (2,3) < (3,4). B) (2,3) < (3,4) < (1,2). C) (1,2) < (3,4) < (2,3). D) (3,4) < (1,2) < (2,3). E) (3,4) < (2,3) < (1,2).

  6. Evolution of Penicillin Resistance by Bacteria • Penicillin discovered in 1896, rediscovered by Fleming in 1928. • Mass-production of penicillin began in 1943. • Staphylococcus aureus, is usually a harmless passenger in the human body, but it can cause pneumonia, toxic shock syndrome, the most common cause of food poisoning. • The first penicillin-resistant strains of “Staph” were isolated in 1947! • 1967, penicillin-resistant Streptococcus pneumoniae and gonorrhea

  7. The First Antibiotic: Penicillin • How Penicillin Kills Bacteria: penicillin attaches to the cell walls of bacteria and destroys a key molecular component of the cell wall. With its cell wall disrupted, the bacterium dies. • Resistant bacteria are not killed by penicillin, they have genes which: (1) alter cell walls to prevent binding by penicillin or (2) produce enzymes that attack the antibiotic: degrade the penicillin.

  8. Staphylococcus aureusis commonly carried on the skin of scalp, arm pit, groin or in the nose of healthy people, and sometimes in canned mushrooms on pizza. It is the most common cause of food poisoning. Common name: the “flesh-eating bacterium.” Staph grows and reproduces from 50 0F to 120 0F, with the most rapid growth occurring near human body temperature (about 98 0F). MRSA commonly occurs in the hospital setting but, more recently community-associated MRSA (CA-MRSA) has been found in correctional facilities and athletic teams.

  9. Geometric Population Growth CA-MRSA cases ranged from 0 to 9 per year from 1990 through 1999 and then increased exponentially from 36 in 2000 to 459 in 2003 459 Number of Cases Of CA-MRSA 36 9 2003 1999 Time in Years • N2003 = b4 N1999 • = b4 (9) implies that b = 2.64! • Finite Resource: Humans! 6,000,0000,000

  10. Hospital Acquired or Nocosomial infections • 1983, resistant Enterococcus faecium, hospital-acquired intestinal infection. • in 1992, 13,300 hospital patients died of antibiotic-resistant bacterial infections • cost of treating hospital infections is $1-3 billion/yr • Patients with noscomial bacteremia spend $3,600 more in direct hospital costs, and remain in hospital 14 days longer than uninfected patients. • 500,000 patients in American hospitals contract a staphylococcal infection each year. 80+% of these are penicillin resistant.

  11. > 50% Methicillin is the antibiotic that replaced Penicillin in 1975. 99 03 > 80%

  12. Vancomycin the drug of last defense In 1992: 13,300 hospital patients died of antibiotic-resistant bacterial infections. For more than a decade, scientists have been dreading but expecting -- an S. aureus strain to emerge that is resistant to vancomycin.

  13. Percentage of hospital Staphylococcus That are multi-drug resistant "It's a serious threat now, and it's getting worse fast. “ 100% 50% 0% Japan Belgium USA Fiji

  14. The “Cost of Resistance” • There is a life history trade-off for bacteria between Anti-biotic Resistance and Reproductive Capacity in the absence of antibiotics. • The bacteria live in 2 Environments: (1) The normal environment with a low level of natural antibiotics produced by competing molds; (2) The hospital, doctor’s office, or animal feed lot environment containing enormous amounts of man-made antibiotics.

  15. What is a Life-History Trade-Off? • It is based on the concept that an organism cannot do everything well. • Football players vs Basketball Players: trade-off between explosive strength (Football) and aerobic endurance (basketball) involving different kinds of muscle and physiology. • “Party”students vs “Serious” students: trade-off between fun and study as a result of finite amount of time. • Growth vs Reproduction: trade-off between acquiring resources for growth and expending resources for reproduction.

  16. Evolution in Two Environments • Two kinds of bacteria: (1) ABS, Anti-Biotic Sensitive (2) ABR, Anti-Biotic Resistant • These bacteria live in 2 Environments: (1) The normal environment low level of antibiotics produced by competing molds; (2) The hospital, doctor’s office, animal feed lot:environments with vast amounts of man-made antibiotics.

  17. The Cost of Resistance: a Life History Trade-Off for the bacterium • In the normal environment, E1 ABS, Anti-Biotic Sensitive bacteria grow faster than ABR, Anti-Biotic Resistant bacteria because: reproductive capacity: bABS > bABR • In the environments with antibiotics,E2: ABR, Anti-Biotic Resistant bacteria grow faster than ABS, Anti-Biotic Sensitive bacteria because: reproductive capacity: bABR > bABS

  18. Trade-off in Population Growth Normal Environment, No Antibiotics: Antibiotic Environment: Nt Nt Time in Generations Time in Generations bABS > bABR bABR > bABS

  19. Trade-off = X AB-Sensitive High b, Reproductive Capacity AB-Resistant Low Anti-bioticsNo Anti-biotics Environments ABR strains Out grow ABS strains ABS strains Out grow ABR strains

  20. Use of Antibiotics Uncommon Before 1950 Anti-Biotic Resistance: favored only in the common environment, selected against everywhere else. Hence, there is a High frequency of anti-biotic resistant bacteria in 2006. bABS > bABR bABR>bABS Rare Environment in 1950: Anti-biotics present ABRstrains favored Common Environment in 1950: No anti-biotics ABSstrains favored

  21. Antibiotics Common After 1950 Anti-Biotic Sensitive: favored only in the rare environment, selected against everywhere else. Hence, there is a low frequency of anti-biotic sensitive bacteria. bABR > bABS bABS>bABR Common Environment in 2006: Lots of anti-biotics ABRstrains favored Rare Environment in 2006: Anti-biotics Absent ABSstrains favored

  22. Change in Use of Antibiotics = Change in the Frequency of the 2 Environments • Anti-biotic Environments were Rare Before 1950 but became Common After 1970 • 1985: 6 million antibiotic prescriptions for sinusitis, Streptococcus pneumoniae and Haemophilus influenzae common upper respiratory tract bacterial species • 1992: 13 million prescriptions for sinusitis • 1985: 15 million prescriptions for middle ear infections, Streptococcus pneumoniae bacteria 1992: 23.6 million prescriptions for middle ear infections

  23. Feedlot Use of Antibiotics • 19 million pounds of antibiotics per year are fed to farm animals, and 88 percent of that amount was fed at low doses, which favor evolution of antibiotic resistance because they do not kill all bacteria in a colony. • 36 million antibiotic prescriptions at 1.5 grams per prescription. • (36 million scripts) (1.5 g) = 54 million grams • 8.6 trillion grams in feedlots vs 54 million grams in prescriptions

  24. Man-made alteration of the environment by industrial pollution changes natural selection on white and black color morphs of the moth, Biston betularia. Man-made alteration of the environment by use of antibiotics to combat disease in humans and domestic animals changes natural selection on sensitive and resistant morphs of Staphylococcus aureus

  25. Environmental Variation and Genetic Trade-offs • Together, environmental variation and a genetic trade-off means that more than one genetic kind of individual will be maintained in the population. • More than one environment, More than one Genetic Strategy for Survival.

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