Interaction & Interdependence C.7 Defence Against Disease (id: 9d9c69944)

本题目来源于试卷: Interaction & Interdependence C.7 Defence Against Disease，类别为 IB生物学

[填空题]
In a classroom investpkwuytn;1 :dn-4j 3ncil;3 .m c blq,figatjiid7 +5 yhmw*ion into the effects of herbal remedies on bacterial infections, students selected a range of herbal teas, marketed as possessing “Immune System B7h5j*dywi +im oosting” properties. Teas each contained one main ingredient, in addition to other secondary ingredients, present in lower concentrations.
A concentrated solution of each tea was prepared and a 0.2 g mass of cotton wool was soaked in each.
A petri dish was prepared using nutrient agar gel and inoculated with a strain of Staphylococcus aureus. The masses of cotton wool were each placed on the petri dish, which was then incubated at 20
o
C for 5 days, after which the zone of inhibition for each mass of cotton wool was measured.


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The experiment was repeated 3 times, a mean and standard deviation was calculated. Results are shown below.


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1.1State the dependent variable in this investigation.

1.2Identify one control variable from the methodology.

2.1Based on the results, suggest which ingredient is most effective at inhibiting the growth of bacteria. Give a reason for your answer.

2.2State the TWO brands of tea whose results are unlikely to show statistically significant differences. Give a reason for your answer.

3.Calculate the size of the inhibition zone for EterniTea as a percentage of the size of that for ResisTea.  

4.Outline the techniques which should be employed in order to reduce risk when working with bacterial cultures.

5.1Identify a limitation of the methodology in allowing a valid comparison of each tea brand.

5.2State how the size of the error bars could be reduced.

参考答案: 333%


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