20.5 Evolution

Question 1

what is the gene pool?

Answer 1

sum total of all the genes in a population

Question 2

what is the allele frequency?

Answer 2

the relative frequency of a particular allele in a population

Question 3

what is evolution?

Answer 3

the change in allele frequencies in a population over time

Question 4

what is p in p+q = 1

Answer 4

the frequency of the dominant allele

Question 5

what is q in p+q = 1

Answer 5

the frequency of the recessive allele

Question 6

what are the conditions of the Hardy-Weinberg Principle?

Answer 6

• there are no mutations
• there is no emigration/immigration
• there is no selection
• mating is random
• the population is large

Question 7

why is the Hardy-Weinberg Principle flawed?

Answer 7

it is very unlikely for a population to meet all of its conditions
THEREFORE
its is theoretical NOT realistic

Question 8

what is p2 in
p2 + 2pq + q2 = 1

Answer 8

frequency of homozygous dominant genotype in a population

Question 9

what is q2 in
p2 + 2pq + q2 = 1

Answer 9

frequency of homozygous recessive genotype in a population

Question 10

what is 2pq in
p2 + 2pq + q2 = 1

Answer 10

frequency of heterozygous genotype in a population

Question 11

what factors lead to changes in the allele frequency within a population?

Answer 11

mutations
sexual selection
gene flow
genetic drift
natural selection

Question 12

how do mutations change the allele frequency?

Answer 12

they are the reason for new alleles being produced which leads to genetic variation

Question 13

how does gene flow change the allele frequency?

Answer 13

emigration/immigration leads to changes in the allele frequency with populations increasing

Question 14

how does genetic drift change the allele frequency?

Answer 14

a new allele will have a greater impact on a smaller population than a larger population as there are fewer alleles in the gene pool

Question 15

what is genetic drift?

Answer 15

the change in allele frequency due to random chance

Question 16

how does natural selection change the allele frequency?

Answer 16

increases the number of organisms with the survival characteristics which, after reproduction, leads to an increase in allele frequency

Question 17

what is the genetic bottleneck effect?

Answer 17

when a population is greatly reduced in size which limits its genetic diversity

Question 18

how did elephant seals suffer from the bottleneck effect?

Answer 18

they were heavily hunted in the 1800s
eventually population was only 20
now have a larger population of 30,000
BUT
now have a lower genetic diversity as the gene pool has been massively reduced so needs many generations to recover

Question 19

what is the founder effect?

Answer 19

when a smaller population, which has a much smaller gene pool, is at greater risk to rare alleles which are now more frequent due to a lack of genetic variation

Question 20

how did the Amish people suffer from the founder effect?

Answer 20

Amish people had a small closed community who mainly interbred

this led to a small gene pool where there was a higher frequency of rare genetic diseases

Question 21

what are the 3 types of selection?

Answer 21

stabilising
directional
disruptive

Question 22

what is stabilising selection?

Answer 22

the extremes are selected AGAINST
and the average is selected FOR

leads to increase in the average characteristic alleles
leads to reduction in the extreme characteristic alleles

Question 23

what is an example of stabilising selection?

Answer 23

a baby’s weight:
- babies who are over or under weight (so an extreme) are less likely to survive
- babies who have an average weight are more likely to survive

Question 24

what is directional selection?

Answer 24

one of the extremes is selected FOR
the other extreme is selected AGAINST

leads to increase in the allele frequency of one extreme
leads to reduction in the allele frequency of the other extreme

Question 25

what is an example of directional selection?

Answer 25

moth colour:
- industrial revolution led to darkening which made light moths stand out
- this also camouflaged the black moths
- over time the white moths were eaten (one extreme against)
- and the black moths reproduced and survived (one extreme for)

Question 26

what is disruptive selection?

Answer 26

both extremes are selected FOR
the average is selected AGAINST

leads to increase in the allele frequency of both extremes
leads to decrease in the allele frequency of the average