Lecture 12

Question 1

what is the problem with pesticides

Answer 1

chemicals are used to fight pests, insects but we create a lot of selection on the resistant variants in the pests
- superweeds, horseweed

Question 2

where does resistance come from

Answer 2

1. genetic variation in the population
2. mutations
3. gene flow
   knowing where the resistance evolved from = helps beat it

Question 3

T/F weeds that use selfing as a mating system have more genetic diversity

Answer 3

false - outcrossing mating weeds = more genetic diversity = more resistant

Question 4

T/F a weed can have many different reasons for the cause of the resistance

Answer 4

true
resistance can evolve through variation, dispersal (gene flow), and new mutations

Question 5

how can we stop the resistance in herbicides

Answer 5

1. multi-herbicide treatment
   - multiple herbicides at once make it less likely for the species to be resistant to them all - HIV, chemotherapy
2. rotation of different types of herbicides
   - one chemical for some time, new chemical for the next period = species are hit with different selection pressures each period - weeding out the resistant alleles
   - although this can cause a superweed (generally resistant to all sprays)

Question 6

why is it seen that more agressive pesticide treatement = more resistant species

Answer 6

more pesticide = risk of dying population = very strong selection pressures for the resistant allele
- a less aggressive treatment = less resistant evolution

Question 7

how does chemotherapy work for cancer treatement

Answer 7

using the same drugs = selection for resistance = not the best solution
cycling drugs and using a multidrug cocktail with lower doses = better option

Question 8

how are humans causing rapid environmental changes

Answer 8

we are impacting species by
- loss of habitat
- habitat fragmentation
- altering temp, pH, salinity, chemical pollutants
- invasive species, transportation of species
global warming = polar bears

Question 9

T/F if earth was undisturbed we would have 1 species extinct every 10 years

Answer 9

true - a low rate compared to now
lots of extinction - especially small organisms

Question 10

when trying to conserve biodiversity what are some genetic issues that arise when the populations get small

Answer 10

loss of genetic diversity from death of animals (decrease hetero)
- inbreeding depression
- fixation of bad mutations
- **inability of populations to adapt

Question 11

what are the factors that species will depend on if they were to be rescued by adaption

Answer 11

depends on population size, beneficial mutation rate and favoritism, how much the fitness was reduced by to gain it back