Natural Selection

1
Natural Selection

• Antibiotic Resistance

2
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?

3
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

4
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

5
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

6
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

7
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

8

• 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

9

• 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?

10
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