3.31

3.31 describe the process of evolution by means of natural selection

Evolution: 1) Change in the form of organisms (new forms rising)

2) Change in the frequency (how many) of alleles

Natural Selection: is the mechanism of evolution first proposed by Charles Darwin (it is a process)

EXAMPLE:

Staphylococcus aureus causes skin infection and lung infection from wounds (e.g. operation wounds).

Methicillin is an antibiotic that kills MSSA (Methicillin Susceptible Staphylococcus Aureus).

A random mutation occurs à develop of breaking down methicillin à no longer killed by this antibiotic à RESISTANT FORM

Now there are two forms of these bacteria (definition of evolution 1).

When antibiotics are applied, the MRSA (Methicillin Resistant Staphylococcus Aureus) survive and become common à increase in frequency of allele for resistance (definition of evolution 2)

2 features of natural selection (process)

- Random mutation à produces MRSA

- Non-random selection due to the antibiotic à selects MRSA à to survive, MSSA selected and killed