Booklet 12- genetic change in populations

Question 1

Define natural variation

Answer 1

Natural variation refers to the genetic diversity of a single species in the wild

Question 2

What are the sources of variation?

Answer 2

1. Mutations cause new alleles to rise in a population
2. Different allele combinations can give different phenotypes
3. Enviornmental pressures
4. Changes in chromosomes

Question 3

Define population

Answer 3

Population refers to an interbreeding group of organisms of the same species, living in the same place, at the same time

Question 4

Define gene pool

Answer 4

Gene pool is the total sum of genetic information (alleles) in a population at any one time

Question 5

Distinguish between genotype and gene pool

Answer 5

Genotype is the total genetic information of an individual. Whereas gene pool is the total genetic information in a population.

Question 6

What factors will keep allele frequencies constant?

Answer 6

1. Large population
2. No migration
3. No mutations
4. No selection pressures

Question 7

What are the 3 agents?

Answer 7

Agents are factors that can cause allele frequencies to change over time

1. Environmental selection pressures
2. Genetic drift (founder and bottleneck)
3. Gene flow (immigration and emigration)

Question 8

Explain Larmarck’s view

Answer 8

Organism changes when it needs to. Structure change and disappear.

Question 9

Explain Darwin’s view

Answer 9

Darwin’s view is natural selection. That one phenotype has a greater chance of surviving in a particular environment. These organisms have a greater chance of surviving and passing their alleles on to next generations.

Question 10

Define environmental selection pressure

Answer 10

Environmental selection pressure are external agents which influence the ability for an individual to survive

Question 11

Define Fitness Value

Answer 11

Measure of genetic contribution to next generations

Question 11

Define adaptation

Answer 11

Characteristic that suits an organism to its way of life and aids survival

Question 12

Define selective advantage

Answer 12

Phenotype which has a higher fitness value in a particular environment

Question 13

Define selective agent

Answer 13

Environmental factor that acts on a particular phenotype

Question 14

Define random mating

Answer 14

Situation that applies in a population when all possible matins are equally likely to occur

Question 15

Define complete selection

Answer 15

Against a phenotype occurs when any organism with a given phenotype cannot reproduce because of death before reproductive age is reached

Question 16

Define partial selection

Answer 16

Against a phenotype occurs when mating involving that phenotype produce on average fewer viable and fertile offspring

Question 17

Define natural selection

Answer 17

Natural selection occurs when any selective pressure acts on a population and produces differences in the survival and reproduction rates in that population

Question 18

What are the key words to include when explaining natural selection

Answer 18

1. Mutation is the cause of variation- arise new alleles
2. Selective advantage= greater chance of survivaL (EXPLAIN WHY)
3. Greater fitness value as these selected traits will pass on to next generations
4. OVER TIME change in species has occurred

Question 19

Define genetic drift

Answer 19

Chance factors that cause changes in allele frequencies in a population.
Change is unpredictable and no allele is favoured over another.

Question 20

Explain alleles being lost and fixed

Answer 20

Alleles being lost means frequency becomes 0%
Fixed means that allele is the only allele present (100%)

Question 21

Define bottleneck effect

Answer 21

Bottleneck effect refers to when size of a population is reduced for at least one generation, leaving small, unrepresentative amount of individuals.

Question 22

Examples of bottleneck effect

Answer 22

1. Natural disaster (flood, earthquake)
2. Heavy predation
3. Human activity
4. Mutations

Question 22

What are the consequences of a bottleneck effect?

Answer 22

1. Decrease genetic variation as only a small, unrepresentative number of individuals have to interbreed and grow the population.
2. Thus, greater risk of extinction.
3. CHANGE IN ALLELE FREQUENCIES

Question 23

Define founder effect

Answer 23

Founder effect is when a small number of individuals from a population migrates/ becomes isolated from the original population. (cannot return back)

Question 24

Explain founder effect

Answer 24

Founder population will have a small, unrepresentative sample of alleles from the parent population’s gene pool. Genetic diversity will be very low, greater chance of extinction.
Founder population will evolve differently to the parent’s population.

Question 25

What is another consequence of founder effect on a population?

Answer 25

Founder effect may also be the cause of unusually high incidences of a particular genetic disease in a geographical location.

Question 26

Define gene flow

Answer 26

Gene flow is the movement of genes into our out of a population

Question 27

Why are smaller populations more affected by gene flow?

Answer 27

Small populations often have fewer alleles to begin with, so the effects of change in allele frequencies is greater than a stable, large population.