Evolution

Question 1

What is a gene pool?

Answer 1

The sum of all genes in a population

Question 2

What is allele frequency?

Answer 2

The relative frequency of an allele in a population at any given time

Question 3

What 2 equations make up the Hardy-Weinberg Principle?

Answer 3

1. p + q = 1, 2. p² + 2pq + q² = 1

Question 4

What does evolution involve in terms of alleles?

Answer 4

A long-term change in the allele frequencies within a population

Question 5

What is p in the Hardy-Weinberg equation?

Answer 5

Frequency of dominant allele

Question 6

What is q in the Hardy-Weinberg equation?

Answer 6

Frequency of recessive allele

Question 7

What is p squared in the Hardy-Weinberg equation?

Answer 7

Frequency of homozygous dominant allele

Question 8

What is 2pq in the Hardy-Weinberg equation?

Answer 8

Frequency of heterogeneous genotype in the population

Question 9

What is q squared in the Hardy-Weinberg equation?

Answer 9

Frequency of homozygous recessive genotype in the population

Question 10

What 5 assumptions underpin the Hardy-Weinberg principle?

Answer 10

1. No selection 2. No mutation 3. No emigration/immigration 4. Random mating 5. Large population

Question 11

What does the Hardy-Weinberg principle state?

Answer 11

That allele frequencies in a population should remain constant unless one or more factors cause those frequencies to change

Question 12

Do populations tend to follow the Hardy-Weinberg principle in the real world? Why/why not?

Answer 12

No as the conditions/assumptions rarely tend to be met

Question 13

What 2 things can the Hardy-Weinberg equations be used to calculate?

Answer 13

Allele and genotype frequencies

Question 14

What is genetic drift?

Answer 14

Change in allele frequency caused by random mutations and chance

Question 15

Why is a large population assumed for the Hardy-Weinberg principle?

Answer 15

Because genetic drift occurs much more in small populations

Question 16

Upsetting the Hardy-Weinberg equilibrium may eventually lead to what?

Answer 16

Evolution

Question 17

Why are small populations more likely to become extinct?

Answer 17

They tend to have lower genetic diversity and so are worse at responding to change- for example, a pathogen could wipe out an entire population

Question 18

What is a genetic bottleneck?

Answer 18

When a sudden environmental change drastically reduces the size of the population for at least a generation

Question 19

What happens to genetic diversity when a genetic bottleneck occurs?

Answer 19

It is greatly reduced for a long period of time

Question 20

What is a positive effect of a genetic bottleneck?

Answer 20

A beneficial mutation will have a much greater impact and lead to quicker development of a new species

Question 21

What is the founder effect?

Answer 21

The reduced genetic diversity that results when a population is descended from a small number of colonizing ancestors. The new population can also be very genetically different from the one its founders split off from due to genetic drift and random presence of some alleles in the founders

Question 22

What is the founder effect an extreme example of?

Answer 22

Genetic drift

Question 23

What form will the distribution of different variants of characteristics take?

Answer 23

A bell curve (standard distribution)

Question 24

What happens in stabilising selection?

Answer 24

Average individuals are favoured

Question 25

What happens in directional selection?

Answer 25

Individuals are favoured in one direction

Question 26

When does directional selection occur?

Answer 26

When there is a change in the environment and the most common phenotype is no longer the most advantageous, so organisms with more extreme phenotypes are favoured

Question 27

What happens in disruptive selection?

Answer 27

The extremes are selected for and the average is selected against

Question 28

What is the opposite of stabilising selection?

Answer 28

Disruptive selection

Question 29

What is speciation?

Answer 29

The formation of new and distinct species in the course of evolution

Question 30

What form of speciation is the most common?

Answer 30

Allopatric speciation

Question 31

What is the sequence of events for speciation?

Answer 31

1. Members of a population become isolated and no longer interbreed with the rest of the population, so no gene flow between the groups 2. Random mutation within the groups continues, but each may have different selection pressures 3. Eventually mutations and changes in allele frequency will mean that both populations are so different that they can no longer interbreed and produce fertile offspring

Question 32

What happens in allopatric speciation?

Answer 32

A population is geographically isolated, and due to different environmental selection pressures speciation occurs

Question 33

What happens in sympatric speciation?

Answer 33

Speciation occurs despite the two populations sharing the same habitat

Question 34

What is a reason that sympatric speciation may occur?

Answer 34

Two different species can interbreed and form fertile offspring which has a different chromosome number from either parent species, thus meaning that the new population is genetically isolated

Question 35

What do prezygotic reproductive barriers do?

Answer 35

Prevent fertilisation and formation of a gamete

Question 36

What do postzygotic reproductive barriers do?

Answer 36

Reduce the viability or reproductive potential of offspring

Question 37

What often forms postzygotic reproductive barriers?

Answer 37

Hybridisation

Question 38

What are 4 examples of problems with artificial selection?

Answer 38

1. Makes more docile animals which can't compete or fight with wild animals 2. Makes more lean animals which could get cold or suffer if food stocks decline 3. Coat colour might not suit environment 4. Inbreeding exacerbates genetic conditions and problems

Question 39

What is artificial selection?

Answer 39

The selective breeding of plants and animals by humans to produce desirable traits

Question 40

What are 2 reasons artificial selection reducing genetic diversity is a bad thing?

Answer 40

1. More susceptible to genetic diseases 2. Potentially useful alleles for the future are lost

Question 41

What are 2 problems with artificial selection?

Answer 41

1. Can cause health problems by exaggerating certain negative traits 2. Reduces genetic diversity

Question 42

What is a species?

Answer 42

A population of genetically similar individuals whose members can interbreed and produce fertile offspring

Question 43

What are 3 types of changes which can cause reproductive isolation, with one example for each?

Answer 43

1. Seasonal changes i.e. different mating seasons 2. Mechanical changes i.e. changes in genitalia prevent successful mating 3. Behavioural changes i.e. different courtship rituals developing

Question 44

What is inbreeding?

Answer 44

Mating between closely related individuals

Question 45

What is outbreeding?

Answer 45

The breeding of distantly related individuals of a species

Question 46

How can the problems of inbreeding be mitigated?

Answer 46

Using alleles from gene banks to do outbreeding

Question 47

What 2 things does outbreeding do?

Answer 47

1. Reduced incidence of homozygous recessives 2. Increases the potential to adapt to environmental change

Question 48

What do seed banks do?

Answer 48

Keep seeds from both wild type and domesticated varieties of plants

Question 49

What do gene banks do?

Answer 49

Similar to seed banks but keep biological samples other than seeds such as sperm or ova, usually frozen

Question 50

What are both seed and gene banks?

Answer 50

An important genetic resource