[9.4] types of selection

Question 1

what is the core of natural selection?

Answer 1

• there is genetic diversity in a population due to random mutations
• the ability to reproduce and pass on alleles
• presence of limited resources leads to competition for these resources
• those that are better adapted will produce the most offspring, passing on advantageous alleles
• over many generations, desired allele will increase in frequency
• differential survival and reproduction: some members of the population will survive while others will die without reproducing

Question 2

what is a gene pool?

Answer 2

set of all genes in any population of a particular species

Question 3

what is a selection pressure?

Answer 3

an environmental factor which affects the reproductive success of organisms in a population

Question 4

what are 3 types of natural selection?

Answer 4

1. individual selection
2. sexual selection
3. kin selection

Question 5

what is individual selection?

Answer 5

the factors determining the number of offspring produced by an individual over its lifetime

Question 6

what is sexual selection?

Answer 6

when members of one sex choose who to mate with, leading to higher reproductive success in some over others

Question 7

what is kin selection?

Answer 7

when the reproductive success of relatives is favoured over survival of individuals

Question 8

what are two types of natural selection that affect the allele frequency in different ways?

Answer 8

1. stabilising selection
2. directional selection

• also disruptive selection

Question 9

describe directional selection (make this scaffold specific for each question)

Answer 9

1. there is a change in the environment
2. individuals with a more extreme adaptation survive
3. individuals with the less extreme alleles die
4. there is less competition and individuals with a more extreme adaptation breed and pass on this allele
5. frequency of allele for more extremely adapted allele increases in the population
6. mean allele shifts in this direction
7. total number of alleles stays the same

• draw the graph!

Question 10

describe stabilising selection (make this scaffold specific for each question)

Answer 10

1. environment stays the same
2. individuals’ alleles for extreme characteristics die
3. individuals with alleles for mean characteristic have an advantage and are more likely to survive
4. there is less competition
5. individuals with average characteristic reproduce, passing on their alleles
6. range of allele type is decreased

• draw the graph!

Question 11

describe disruptive selection (make this scaffold specific for each question)

Answer 11

1. both extremes are advantageous
2. individuals with alleles for an average characteristic are more likely to die
3. individuals with characteristics for both extremes reproducing, passing on their alleles
4. frequency of average alleles decreases, frequency of low and high alleles increase

• draw the graph!

Question 12

what type of adaptations can natural selection result in?

Answer 12

• anatomical (eg. shorter ears and thicker fur in arctic foxes)
• physiological (eg. oxidising fat rather than carbohydrate in kangaroo rats to produce additional water in dry desert environment)
• behavioural (eg. autumn migration of swallows from UK to africa to avoid food shortages in UK winter)