4.4 Genetic diversity and selection

Question 1

what is genetic diversity

Answer 1

the number of different alleles for a gene in a population

Question 2

what is natural selection and how does it occur

Answer 2

• there is genetic diversity in the population
• new alleles arise due to random mutation
• the population experiences selection pressure
• individuals with the advantageous allele survive to reproduce
• the advantageous allele is inherited by offspring
• therefore, over many generations, the advantageous allele increases in frequency in the population

Question 3

what are adaptations that can occur for survival

Answer 3

• anatomical
• physiological
• behavioural

Question 4

what are anatomical adaptations

Answer 4

fur colour, neck length

Question 5

what are physiological adaptations

Answer 5

rate of gas exchange, muscle contraction efficiency

Question 6

what are behavioural adaptations

Answer 6

courtship displays

Question 7

how do species characteristics change

Answer 7

• all organisms have a range of phenotypes
• for polygenic traits, the observed phenotypes show normal distribution
• stabilising selection or directional selection can occur

Question 8

what is stabilising selection

Answer 8

the intermediate (middle) phenotypes are best adapted to survival in the environment so are advantageous
- the intermediate phenotypes are more common and extreme phenotypes may disappear

Question 9

example of stabilising selection

Answer 9

birth mass in humans

Question 10

what is directional selection

Answer 10

• an extreme phenotype is best adapted to survival in the environment so a particular allele is advantageous
• the extreme phenotypes become more common

Question 11

example of directional selection

Answer 11

antibiotic resistance in bacteria