Microevolution IV: Natural Selection II

Question 1

equation to find the freq of gtypes after selection has operated

Answer 1

p^2 x W A/A = #
2pq x W A/a = #
q^2 x W a/a = #

sum all numbers to get a number less than 1

Question 2

equation for relative fitness (w bar)

Answer 2

p^2W A/A + 2pqWA/a + q^2 W a/a

Question 3

to find the freq in the next gen after selection

Answer 3

A/A: (p^2W A/A) / w bar
A/a: (2pqW A/a) / w bar
a/a: (q^2 W a/a) / w bar

Question 4

effects of NS wrt HWE

Answer 4

selection can cause allele freq to change gen to gen
selection can cause deviation from HWE gtype freq b/c of diff types of fitness
selection is deterministic/predictable always in the case of a single locus w/ 2 alleles where 1 is favored and other is deleterious
selection is a STRONG evol force

Question 5

Evol by NS, darwins postulates

Answer 5

indiv vary
at least some variation is heritable
some indiv leave more progeny than others b/c of variants
variation in survival & repro is not random, but depends on heritable trait variation
expected outcome: genetic variants w/ higher survival and/or repro inc in freq in pop and lower will dec

Question 6

what are the 3 diff mechanisms of genetic variation preservation

Answer 6

diploidy
hetero adv
freq dependent

Question 7

define balancing selection

Answer 7

NS maintaining stable freq of at least 2 phenotypic forms in a pop
2 diff types: freq dependent & hetero advantage

Question 8

hetero adv

Answer 8

sickle cell
hetero hace greater fitness than homo
maintains both alleles
gtype freq changes, allele freq don’t change, variation maintained

Question 9

freq dependent selection

Answer 9

fitness of any morph varies wrt its freq in pop
declines if too common
scale eating fish

Question 10

sexual selection

Answer 10

NS for mating success

2 types: intrasexual and intersexual

Question 11

intrasexual selection

Answer 11

between same sex, usually males fighting for access to mate w females

Question 12

intersexual selection

Answer 12

usually females who are choosy with mates
selection may depend on showiness in males
chances for mating inc while chance for survival may dec

Question 13

define sexual dimorphism

Answer 13

diff between secondary sex characteristics ( ornamentation, behavior)

Question 14

good genes hypothesis

Answer 14

• if a trait is related to male genetic quality or health, both male trait and female preference for that trait. should inc in freq
• doesnt imply all sexually selected traits are due to good genes, but rather if a particular trait is correlated w/ quality of health, freq of females that prefer that trait inc
• mated female frog w a LC and short call frog
  
  • offspring from LC better survival than SC, and females prefer LC over short