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6 marksNatural Selection

CAPE Biology Unit 1 · May/June 2019 · Paper 2 · Question 2(a)(i)

Table 1 shows the relative growth rates of sensitive and resistant strains of S. typhimurium exposed to varying tetracycline concentrations.

Plot a line graph on the grid provided showing the relative growth rate (y-axis) vs tetracycline concentration (x-axis) for both the sensitive and resistant strains of bacteria.

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Other parts of this question

  1. 2(a)(ii)Outline the effect of antibiotic concentrations of 0.1 ug/ml and 0.7 ug/ml on BOTH bacterial populations.[4 marks]
  2. 2(a)(iii)Explain how the differences between the growth rates of the bacteria could lead to natural selection.[4 marks]
  3. 2(b)(i)Complete the missing codons in the boxes labelled A and B in Figure 3.[2 marks]
  4. 2(b)(ii)With reference to the mutation in Figure 3, explain how mutation brings about genetic variation at the DNA, protein and cellular level.[6 marks]
  5. 2(c)Discuss the process of natural selection as proposed by Darwin to be the mechanism of evolutionary change.[8 marks]

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