Evolution Chapter 9.1

Question 1

What is a gene pool?

Answer 1

All the alleles of all the genes of all individuals in the population

Question 2

What is allele frequency?

Answer 2

The number of copies of a particular allele compared to the total number of alleles in a population’s gene pool

Question 3

What leads to evolution within a population/microevolution?

Answer 3

The changing percentages or frequencies of alleles within populations

Question 4

What are the common factors that lead to evolutionary change?

Answer 4

1. Mutation
2. Natural Selection
3. Non-random mating
4. Gene flow (migration)
5. Genetic drift
   (MNNGG)

Question 5

How do mutations lead to evolutionary change?

Answer 5

1. Random introduction of new alleles into gene pool
2. Changes allele frequencies
   Ex: anti-biotic resistance in bacteria

Question 6

How does gene flow lead to evolutionary change?

Answer 6

1. Movement of alleles from one population to another due to migration and interbreeding
2. May change allele frequencies in either or both populations

Question 7

What is non-random mating?

Answer 7

Mating among individuals on the basis of mate selection for a particular phenotype or due to inbreeding

Question 8

What are the two types of non-random mating?

Answer 8

1. Preferred phenotypes

2. Inbreeding

Question 9

How does preferred phenotype relate to non-random mating?

Answer 9

• Mates chosen based on physical and behavioral traits (phenotype)
• Mates with desirable trait will pass down phenotype to offspring

Question 10

What is sexual selection?

Answer 10

• Competition for female from males (fighting, displays)

Question 11

What is sexual dimorphism?

Answer 11

Significant physical distinctions between sexes

Question 12

What is inbreeding?

Answer 12

Closely related individuals breed together

Question 13

How does inbreeding and non-random mating relate?

Answer 13

• Increases the frequency of homozygous genotypes
  Negative effects:
• Homozygous genotypes are common between close relatives and harmful recessive alleles are more likely to be expressed

Question 14

What is genetic drift?

Answer 14

Random change in allele frequencies due to chance events in a breeding population

Question 15

What is the difference between sample size and population size?

Answer 15

1. Population size can greatly affect the gene pool of a population (less likely that parent gene will be reflected in next generation) - vice versa for large population size
2. Smaller sample size, greater uncertainty

Question 16

What are the two significant genetic drifts and what leads to them?

Answer 16

1. Bottleneck Effect
2. Founder Effect
   Population size and sample size

Question 17

What is the bottleneck effect?

Answer 17

• Population changes size quickly (reduced) because of natural happenings (disaster, disease)
• Survivors had an allele that only a fraction of the population had before the disaster and gene pool is loses diversity
• Survivors carry some, but not all, of original alleles

Question 18

What is the founder effect?

Answer 18

• Change change in gene pool when a few individuals (“founders”) start a new, isolated population
• Founders carry some but not all alleles of original population

Question 19

What are the three modes of natural selection?

Answer 19

1. Stabilizing selection
2. Directional selection
3. Disruptive selection
   (SDD)

Question 20

What is stabilizing selection?

Answer 20

• Favours middle phenotype over extremes
• Reduces variance
• Graph: vertically stretched from original graph
  Ex: Middle colour clams are able to survive than the extreme light/dark clams because they are easy to be spotted by predators

Question 21

What is directional selection?

Answer 21

• Favours one extreme phenotype over other extreme phenotype
• Changes mean value of trait under selection
• Graph: shifted units to the right
  Ex: Oyster shell thickness

Question 22

What is disruptive selection?

Answer 22

• Favours extreme phenotypes over intermediate phenotypes
• Increases variance
• Population is divided into two distinct groups
• Graph: Two lumps
  Ex: Middle coloured clams are not able to survive but the extreme light/dark are able to survive

Question 23

What type of selection leads to the formation of new species?

Answer 23

Diversifying selection