2.4 - Population Genetics

Question 1

Darwin’s theory of natural selection (3)

Answer 1

1. variation in populations
2. inherited traits
3. competition for survival

Question 2

A allele and a allele frequency equations

Answer 2

1. A allele frequency:
   ((2 x AA) + (1 x Aa))/(2 x total)
2. a allele frequency:
   ((2 x aa) + (1 x Aa))/(2 x total)

Question 3

Hardy-Weinberg assumptions (5)

Answer 3

1. only sexually reproducing diploid organisms
2. no mutation or ongoing evolution of alleles
3. no genetic drift
4. random mating
5. no gene flow in/out of populations

Question 4

Natural selection requirements (3)

Answer 4

1. genetic variation in population
2. variation must affect survival/reproductive success
3. stable environment

Question 5

term for likelihood to survive and reproduce

Answer 5

fitness

Question 6

absolute fitness

Answer 6

fitness of individual

Question 7

relative fitness

Answer 7

fitness of individual with particular genotype relative to other genotype

Question 8

3 types of selection (3)

Answer 8

1. stabilising selection
2. directional selection
3. disruptive selection

Question 9

stabilising selection (2)

Answer 9

• individuals close to mean have highest fitness
• mean doesn’t change, variation reduced

Question 10

directional selection (2)

Answer 10

• individuals at one extreme have highest fitness
• evolutionary trend towards extreme

Question 11

disruptive selection (2)

Answer 11

• individuals at both extremes have high fitness
• variation in population increases, results in bimodal pattern

Question 12

genetic drift

Answer 12

random events leading to survival/death of random genotypes, aren’t linked to adaptation or fitness

Question 13

population bottleneck

Answer 13

large population declines, gene pool of reduced population doesn’t represent original population

Question 14

causes of population bottleneck examples (4)

Answer 14

1. Volcanic eruption
2. Earthquake
3. Over-hunting
4. Radiation poisoning

Question 15

founder effects

Answer 15

few individuals colonise new location, gene pool not representative of original location

Question 16

examples of non-random mating (3)

Answer 16

1. assortative mating
2. positive assortative mating
3. negative assortative mating

Question 17

assortative mating

Answer 17

mates chosen based on genotype/phenotype

Question 18

positive assortative mating

Answer 18

mates chosen based on similar genotype/phenotype

Question 19

negative assortative mating

Answer 19

mates chosen based on dissimilar genotype/phenotype