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About the question:
You will find the diagram used to answer the question in the attached files.
Answer:
D) Some of the bacterial population was resistant to this antibiotic.
Explanation:
The term resistance refers to an inheritable change in a population sensitivity, reflected through the consecutive failure of the chemical effects, correctly used to reach a desired effect on the target population.
The excessive use of antibiotics on the bacteria population leads to the fixation of new mutated genes -by natural selection-. The mutated genes make these cells even more resistant to the drug.
In the exposed example we have,
- Day 1 ⇒ a big population of white bacteria and only one black cell, probably <em>carrying mutated genetic material</em>.
The population was treated with antibiotics.
- Day 2 ⇒ there are fewer white bacteria and three black cells. This means that white bacteria are dying, while the black ones are reproducing.
The mutated phenotype gets to survive under the effects of the chemical.
- Day 3 ⇒ There are no more white bacteria. Only the black population survived and keeps reproducing.
The mutated bacteria reproduce with the capability of tolerating the antibiotic dose that is usually used to destroy a population of white bacteria.
- Day 4 ⇒ Black bacteria got to survive a produce a big population. Remember that <em>bacteria follow the exponential growth model, </em>meaning that their reproductive rate is too high. This black population survived the antibiotic action and reproduced at high rates.
