Lecture 24

Question 1

Pests and evolution problem

Answer 1

• We use chemicals to combat pests and pathogens
  
  • Weeds, insects, bacteria, tumors
  • We create strong selective pressure for resistance
  • Fitness advantage to resistant genotypes arising from mutation and gene flow

Question 2

Weeds and Agriculture

Answer 2

• Weeds cause approx. 34% loss of crop yields annually
  
  • Weeds compete with crops for light, nutrients, space
  • 26 bill in loses
  • Spray with herbicides
  • BUT HUGE RESISTANCE TO HERBICIDES BUILDING

Question 2

Where does resistance come from

Answer 2

1) Pre existing genetic variation in population
2) Gene flow
- Epidemic spread of resistance from one region to the next
3) New mutations
- In very large populations new, simple mutations may be introduced at a high rate
Wises management depends on how resistance tends to evolve
Out crossing weeds have more pre-existing resistance variation than selfing weeds

Question 3

Can Herbicide Resistance be stopped

Answer 3

1) Multi-herbicide treatment makes new adaptation less likely, requires more complex adaptation
2) Rotation of different kinds of herbicides, weeds regularly hit by selective pressures
BUT = could select for generalized resistance

Question 4

Malaria and Mosquitoes

Answer 4

major prevention strategy is insecticide, strong selective pressure on mosquitoes has led to rapid evolution of resistance
- Tailor insecticide’s application to knowledge of mosquito generation times and spatial distributions
- Minimize selection for mosquitoes resistance while reducing malaria transmission
- Less aggressive drug treatment of malarias in mice resulted in less evolution of resistance, reduced infectiousness and similar health outcomes

Question 5

Multi drug cocktails slow evolution of HIV resistance

Answer 5

• Different mechanisms of action
  
  • Low viral loads make multiple mutations less likely

Question 6

CANCER

Answer 6

• Chemotherapy may not be best, selects for resistance
  Drug cocktail may be better option

Question 7

CLIMATE CHANGE

Answer 7

• Will species adapt?
  Genetic issues
  Loss of genetic diversity
  Loss of heterozygosity
  Inbreeding depression
  Fixation of deleterious alleles

Question 8

EVOLUTIONARY RESCUE DEPENDS

Answer 8

POPULATION SIZE BENEFICAL MUTATION RATE HOW MUCH FITNESS WAS REDUCES