3.4.4 Natural Selection

Question 1

Genetic diversity

Answer 1

• no of different alleles for a gene in a population
• contributed to biodiversity - wider range of phenotypes increases the likelihood of a species surviving in a changing env.
• required for natural selection

Question 2

Natural selection

Answer 2

• there is genetic diversity in the pop.
• new alleles arise due to random mutations.
• the pop. Experiences selection pressure
• individuals with the advantageous allele survive and reproduce
• the advantageous allele is inherited by the offspring
• over generations, the advantageous allele increases in fr, in the population.

Question 3

The species is better adapted after natural selection to survive in the environment. Adaptions can be:

Answer 3

• anatomical e.g. fur colour
• physiological e.g. rate of gas exchange
• behavioural e.g. courtship displays

Question 4

Stabilising selection

Answer 4

• intermediate phenotypes are the best adapted to survival in the environment so these alleles are advantageous.
• intermediate ph more common, extreme ph may disappear
• e.g. birth mass in humans

Question 5

Directional selection

Answer 5

• an extreme phenotype is the best adapted to survival in the environment so a particular allele is advantageous
• the extreme ph becomes more common
• e.g. antibiotic resistance

Question 6

What can mutation be ?

Answer 6

1. Harmful
2. Neutral - do not impact survival
3. Beneficial - the ph increases survival and reproductive success

Question 7

Normal distribution

Answer 7

• for polygenic traits (constant variation) the observed phenotypes show normal distribution
• the middle characteristics are the most common and the extremes are rare.