4.4 Genetic diversity and adaptation

Question 1

What is genetic diversity?

Answer 1

Number of different alleles of a gene in a population

Question 2

Define population:

Answer 2

Group of interbreeding individuals of the same species

Question 3

What are the principles of natural selection in the evolution?

Answer 3

1. Variation of alleles exists in population due to random DNA mutations
   e.g. some bacteria contain gene for antibiotic resistance due to a mutation
2. Selection pressure / change in environment e.g. antibiotic introduced
3. Those with advantageous allele have increased chance of survival and reproduction – differential survival/reproductive success
   e.g. bacteria with gene for resistance survive and reproduce whilst those without it die
4. Those surviving / reproducing pass advantageous allele to offspring
5. Frequency of advantageous allele and (named) characteristic increases in the population
6. Over many generations / long period of time
   (evolution: change in allele frequency over time)

Question 4

What is directional selection?

Answer 4

• Change to the environment
• Selection pressure acts one side of the mean
• One extreme phenotype more likely to survive and produce
  Eg/ Bacteria with gene for antibiotic resistance
• Mean phenotype changes

Question 5

What is stabilising selection?

Answer 5

• Stable environment
• Selection pressure acts either side of the mean
• Both extremes of phenotype less likely to survive and reproduce
  Eg/ Very small or very large babies
• Mean phenotype remains the same