3.31 Evolution

3.31 describe the process of evolution by means of natural selection

Evolution     : Change in the form of organisms
 : Change in the frequency of alleles

Natural selection is the mechanism of evolution (first proposed by Charles Darwin)

If we take Staphylococcus aureus (a skin & lung infection) to show this.

• The original form is susceptible to being killed by the antibiotic methicillin. Known as MSSA (methicillin-sensitive staphylococcus aureus).
• By Random Mutation a form was formed that was resistant to this antibiotic, because it could break down the antibiotic. Known as MRSA (methicillin-resistant staphylococcus aureus).
• This positive change in form of the organism caused the change in frequency of the alleles, because the susceptible organisms began to die out and the frequency of the resistant increased.