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biology 0610printed 248 · PDF 248
328 pagesrevision 46933
printed 248 · PDF 248
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3.
Struggle for survival: Within the population, the individuals
will compete with one another for resources.
4.
Survival of the fittest: Only the individuals that have the
best adaptive features will have the best chance of surviving and
reproducing.
5.
Reproduction: Useful alleles are likely to be passed on since
the better adapted individuals survive for longer and will likely pass
on their alleles to the next generation.
Development of Antibiotic-resistant bacteria
● Adaptation is the process resulting from natural selection in
which populations become better suited to their environment over
many generations.
● Antibiotics were used to kill bacterial cells without harming
human cells but over time bacteria have become resistant to
antibiotics due to natural selection.
● Within a bacterial population, there will be several million
bacteria. Out of these one or two are likely to be resistant to a
specific antibiotic. These bacteria reproduce rapidly while others
die and so they spawn a new population of bacteria that is
completely resistant to that antibiotic.
● Staphylococcus aureus bacteria are one bacteria species that
have been rapidly evolving and adapting to antibiotics.
● To stop bacteria from becoming resistant to antibiotics, we can
restrict use of antibiotics, complete the full medication provided to
us, only use antibiotics for bacteria and only when necessary.
Selective breeding vs Natural selection
● Selective breeding/Artificial Selection is when humans breed
organisms for their own benefits.
● Firstly, they select individual organisms with features they
consider desirable. Second, they cross these individuals to produce