Transcript Natural Selection

Natural Selection
Antibiotic Resistance
What is Antibiotic Resistance?
• Watch the Video Clip
about tuberculosis in
Russian prisons
• Why is the Russian
prison system
considered “ground
zero” in the fight
against TB?
Virus vs. Bacteria
• A virus is non-living,
does not have
organelles, and needs
a host cell to
reproduce
• Bacteria are alive,
have ribosomes, and
can reproduce on
their own
Antibiotics
• Substances that kill
disease causing bacteria
• Fifty years ago, scientists thought that
antibiotics had eradicated certain bacterial
infections
• Now, we are seeing an increase in
infectious disease
What is happening?
• When antibiotics are
used, MOST of the
bacteria are killed.
• Some of the bacteria
have mutated and can
survive even when the
antibiotic is taken
• They are “resistant” to the
antibiotic
Mutation Review
• How does a mutation occur?
– The DNA sequence is changed in some way
– An error occurs during
• Replication
• Transcription
• Translation
– When the bacteria reproduce, this mutation is
passed on to the new bacteria
Natural Selection
• The “resistant” bacteria are the only bacteria to
survive after using antibiotics
• They reproduce rapidly!
• This creates an entire
colony of resistant bacteria
that will not be killed by
antibiotics
• Natural Selection means the survival of
the “fittest”
• What does “fittest” mean?
– Those organisms that can survive and
reproduce
– Adapted to the environment
• The resistant bacteria are the “fittest” and
survive and reproduce
• If the weakest bacteria are killed first, and
you stop taking your antibiotics after five
days of a ten day course, what do you
predict will happen to the population of
bacteria in your body?
Antibiotic Resistance Activity
• Follow the procedure on your lab paper to
simulate what happens when antibiotics
are not taken as prescribed
• Record your data in Table 1 and graph the
data when you are finished
• Complete the analysis questions in your
lab notebook