HWE: Selection - 7

Question 1

Define selection

Answer 1

individuals with certain phenotypes have higher survival and/or reproduction
(phenotypes must be heritable)

Question 2

What are the problems with selection (3)

Answer 2

environmental influences, multigenic traits, and continuous traits (vs. discrete)

Question 3

What happens if there is equal selection on homozygotes

Answer 3

if equal selection pressure starting with equal frequencies, then no changes will occur, but if start with any frequencies that are not equal, then changes will occur.
the genotype frequencies will be affected (heterozygotes will increase), but NOT allele frequencies

Question 4

How fast are the changes in frequencies if there are big vs small differences in selection

Answer 4

small differences in selection will cause big changes over time
large differences will cause changes quickly

Question 5

Define absolute vs. relative fitness

Answer 5

absolute = number of offspring of an organism of a specific genotype
relative = the fitness of a genotype relative to the most (the fittest) genotype

Question 6

the rate of change depends on _____, not ____ fitness

Answer 6

relative
absolute

Question 7

What defines the selection coefficient

Answer 7

relative fitness (w)

Question 8

What does a positive and negative selection coefficient mean

Answer 8

positive = selected against
negative = selected for

Question 9

The best genotype has a fitness of ____

Answer 9

1

Question 10

How do you calculate relative fitness

Answer 10

dividing each genotypes survival and/or reproduction by the highest survival and/or reproduction rate

Question 11

How do you calculate the selection coefficient (s)

Answer 11

relative fitness (w) - 1 = s

Question 12

What occurs after selection depending on if a lethal allele is recessive vs. dominant

Answer 12

if recessive = never fully goes away because it is still present and hidden in heterozygotes
if dominant = it will disappear almost instantly because there is no place for it to hide

Question 13

What are the percentages that determine if an allele is rare or common

Answer 13

rare allele frequency = <5%
common allele frequency >95%

Question 14

How does selection for a rare recessive, common recessive, rare dominant and common dominant influence the allele frequency over time

Answer 14

rare recessive = evolution by selection is slow because they are present in heterozygous individuals
dominant rare (and common recessive) = evolution by selection is fast

Question 15

Does strong selection always result in fixation

Answer 15

No, commonly something else occurs too such as, heterozygous superiority (heterozygous individual has greater fitness than either homozygous) which also prevents the loss of the lethal allele (because it can still hide) or can occur will heterozygote inferiority

Question 16

Define frequency dependent selection

Answer 16

the success of a genotype depends on its frequency in a population

Question 17

Define positive vs. negative frequency dependence

Answer 17

positive = favours common form
negative = favours rare form

Question 18

How is elderflower orchids (yellow or purple) and bees an example of frequency dependent selection

Answer 18

Bees pollinate plants, but they provided no reward for the bees back. So be will pollinate white flower and then not rewarded and then try purple, etc. If there are more white flowers to begin with, overall purple will get pollinated more because get more visits when alternating.