Download KEY Scientific Method in Action – The Discovery of Penicillin

Scientific Method in Action – The Discovery of Penicillin
Read the passage and answer the questions below.
The bacteriologist, Sir Alexander Fleming was engaged in the study of Staphylococcus, a
kind of bacteria that was being grown in Petri dishes. That’s when he noticed the penicillin mold
that was also growing in some of the culture dishes. There was a clear area around the
penicillin because the bacteria that had grown here had died. But there were no clear areas in
the dishes without penicillin.
Sir Alexander hypothesized that the penicillin mold could be producing a chemical that
kills bacteria. He decided to test his hypothesis by isolating the chemical and testing it to see if
it would really kill bacteria. He transferred it to a solution of nutrient broth that contained the
elements necessary to its growth. Once the mold flourished, he removed it from the broth and
transferred the broth to a culture of bacteria. The bacteria died as a result. This discovery was
used to develop several kinds of antibiotics that treated several deadly diseases.
Questions
1.
What is the problem here?
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2.
What was the hypothesis?
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3.
How did Fleming test his hypothesis?
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4.
Did the results of the experiment support or reject Fleming’s hypothesis?
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5.
What was the independent variable in Fleming’s experiment?
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6.
What was the dependent variable in Fleming’s experiment?
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KEY
Scientific Method in Action – The Discovery of Penicillin
Read the passage and answer the questions below.
The bacteriologist, Sir Alexander Fleming was engaged in the study of Staphylococcus, a
kind of bacteria that was being grown in Petri dishes. That’s when he noticed the penicillin mold
that was also growing in some of the culture dishes. There was a clear area around the
penicillin because the bacteria that had grown here had died. But there were no clear areas in
the dishes without penicillin.
Sir Alexander hypothesized that the penicillin mold could be producing a chemical that
kills bacteria. He decided to test his hypothesis by isolating the chemical and testing it to see if
it would really kill bacteria. He transferred it to a solution of nutrient broth that contained the
elements necessary to its growth. Once the mold flourished, he removed it from the broth and
transferred the broth to a culture of bacteria. The bacteria died as a result. This discovery was
used to develop several kinds of antibiotics that treated several deadly diseases.
Questions
1.
What is the problem here?
Bacteria surrounding the penicillin was disappearing. Fleming believed that a chemical
produced by the penicillin was causing the bacteria surrounding it to die.
2.
What was the hypothesis?
If the bacteria in the petri dishes died, then the penicillin in the petri dish produced a
deadly chemical.
3.
How did Fleming test his hypothesis?
He transferred the penicillin to a solution necessary for its growth. Once grown, he
removed the penicillin and added it to a broth containing bacteria. In result, he wanted
to observe whether the bacteria died or survived.
4.
Did the results of the experiment support or reject Fleming’s hypothesis?
The results supported his hypothesis because the bacteria died as a result of the
addition of penicillin.
5.
What was the independent variable in Fleming’s experiment?
The presence or non-presence of penicillin.
6.
What was the dependent variable in Fleming’s experiment?
The survival of bacteria.