Module 6: Evolution

Question 1

State the definition of gene pool

Answer 1

all the number of alleles in a population

Question 2

State the definition of allele frequency

Answer 2

how often an allele occurs in a population

Question 3

Describe how evoultion by natrual selction takes place

Answer 3

• variation caused by mutation
• selection pressure (disease, predation, competition)
• some are better adapted than others
• ones with advantgous allele most lkley to surivve wheras the others may die
• survivours reproduce, so greater proportion of next gen can inherit advantgous allele
• allele frequency increases

Question 4

What does stabalising selection mean

Answer 4

natural selection that keeps allele frequencies relatively constant over generations
characteristics are in the middle range
usually in a stable enviorement

Question 5

What is directional selection

Answer 5

happens in a changing environment

individuals with alleles more to the extreme are more likely to survive

Question 6

How would directional selection occur in an environment

Answer 6

selection pressure favours a particular phenotype
Individuals with the favoured phenotype will survive and are more likely to reproduce and pass on the advantageous alleles to their offspring
others will probably die
So over time and several generations the frequency of the advantageous allele increases
and frequency of other alleles decreases

Question 7

What is genetic drift

Answer 7

it is when chance affects which individuals in a population survive instead of selection pressures

Question 8

How does genetic drift occur

Answer 8

variation in alleles within population
by chance one genotype is passed on more compared to others
so allele frequency of that allele increases
if by chance the allele is passed on, then it can lead to evolution

Question 9

What kind of population does genetic drift mainly occur in

Answer 9

smaller populations

Question 10

What is genetic bottleneck?

Answer 10

it is when an event such as an earthquake causes a previously large population to decrease dramatically in size

this means that one allele will be more common

Question 11

What is the founders effect

Answer 11

it is when a small number of individuals from a large population start a new population, this means there is a small number of alleles in the gene pool
therefore population is more likely to be influenced by genetic drift

Question 12

How does founders affect occur

Answer 12

migration or geographical isolation

Question 13

What is the equation for hardy Weinberg

Answer 13

p + q = 1

p2 + q2 + 2pq = 1

Question 14

What does p mean in hardy Weinberg

Answer 14

dominant allele

Question 15

What does q mean in hardy Weinberg

Answer 15

recessive allele

Question 16

What does 2pq mean in hardy Weinberg

Answer 16

heterozygous alleles

Question 17

What does hardy Weinberg’s principle state

Answer 17

if certain conditions are met then the allele frequencies of a gene within a population will not change from generation to generation

Question 18

What are the conditions of the Hardy Weinberg principle

Answer 18

Organisms are diploid
Organisms reproduce by sexual reproduction only
There is no overlap between generations
Mating is random
The population is large
There is no migration, mutation or selection
Allele frequencies are equal in both sexes

Question 19

Define speciation

Answer 19

evolution of a new species from existing ones

Question 20

What is allopatric speciation

Answer 20

when a population becomme reproudctily isolated through geographical isolation and natural selection

Question 21

What is sympatric speciation

Answer 21

when a population becommes reporoudctivly isolated wihtout a geograhical barieer, this can be because of random mutaions causing mechanical, seasonal or behavioural changes

Question 22

What is sympatric speciation

Answer 22

when a population becommes reporoudctivly isolated wihtout a geograhical barieer, this can be because of random mutaions causing mechanical, seasonal or behavioural changes

Question 23

How would reproductive isolation occur

Answer 23

• Seasonal: different flowering or mating seasons
• mechanical: they may have chnages in genatalia to prevent successful breeding
• Behavioural: courting rituals aren’t the same etc

Question 24

What is artifical selection

Answer 24

process where humans choose organisms with desirable traits and selectively breed them together to ensure desirable traits are expressed over time and over many generations

Question 25

What methods were cows breed to have high yield of milk

so like who was breed with who

Answer 25

• farmers breed selected female cows that have the highest milk yield and crossed them with males who related to high yield females
• they also bred offspring with highest milk yield and they do this over generations

Question 26

What characteristics are cows selected for

Answer 26

• HIgh milk quality
• long lactation period
• large udders
• a calm temperemnet
• resistence to mastitsis

Question 27

What chatracterics are plants selectivly bred for

Answer 27

Disease resistance in food crops
Increased crop yield
Hardiness to weather conditions (eg. drought tolerance)
Better tasting fruits
Large or unusual flowers

Question 28

How is bread wheat bred to together

Answer 28

• wheat plants with high wheat yield are bred together
• offsprings are bred together
• over many generations

Question 29

What characteristics were selected for when breeding wheat

Answer 29

• high tolerance of cold
• short stalks so they don’t collapse
• uniform stalks (makes harvesting easier)

Question 30

Why do we need to maintain a resource of genetic material in artificial selection?

Answer 30

it is important to maintain a resource of genetic material that includes types that are close to the original wildtype (organism you are selectively breeding)

This ensures that the gene pool for a particular species doesn’t become too small which can decrease variation

Question 31

What is inbreeding depression

Answer 31

it is when there is a reduced biological fitness due to inbreeding

biological fitness referees to the ability to

• survive
• reproduce
• can led to harmful recessive alleles being expressed in phenotype

Question 32

How can we prevent inbreedimg depression

Answer 32

by outbreeding with other wild types

Question 33

What are ethical issues with artificial selection

Answer 33

reduction in the gene pool: can cause problems in future because if the disease appears there’s less of a chance that the crops/animals will survive

Increased chance of inheriting diseases through combining recessive alleles

Can cause problems for organisms

• Pugs and French bulldogs suffer from breathing problems
• High incidence of deafness in dalmatians and english bull terriers