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biology 0610printed 326 · PDF 326
328 pagesrevision 46933
printed 326 · PDF 326
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2 Antibiotics are used to treat human diseases.
Many bacteria have become resistant to antibiotics. Some antibiotics can no longer be used
to treat certain diseases.
Samples of bacteria were taken from a person who had an infectious disease. They were
spread onto four Petri dishes of agar (agar plates), Three of these agar plates contained the
antibiotics 1, 2 or 3.
The results are shown in Fig. 2.1.
O7.0@
agar plate contains agar plate contains agar plate contains agar plate contains
no antibiotic antibiotic 1 antibiotic 2 antibiotic 3
key
[Bl bacterial growth
[_] no bacteria
Fig. 2.1
(a) Explain why:
(i) no bacteria grew in the agar plate with antibiotic 2;
All. bacteria arent resistant. ccm
to..antibiotic.2
(1]
(ii) bacteria grew in the agar plate with antibiotic 3;
All.the bacteria present are
[1]
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