IGCSE 2020 Biology 0610/63 May/June

IGCSE 2020 0610/63 May/June (pdf)

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1. A student investigated the effect of concentration on the rate of diffusion in model cells.
   Cubes of agar jelly containing universal indicator were used to represent the model cells.
   (a) A student used a scalpel to cut four identical cubes from a large piece of agar. Each cube had the dimensions shown in Fig. 1.1. Each agar cube was green in colour at the start of the investigation.
   (i) Calculate the surface area and volume for the cube shown in Fig. 1.1.
   Step 1 The student used the information in Table 1.1 to add the appropriate volumes of 1.0 molperdm³ hydrochloric acid (HCl) and water to four test-tubes labelled A, B, C and D.
   (ii) Complete Table 1.1 by:
   

• stating the unit for the final concentration of HCl
• calculating the missing concentration for test-tube B.
  Step 2 One green agar cube was put into each of test-tubes A, B, C and D.
  Step 3 A stop-clock was started.
  Step 4 The student observed the colour change in the agar cubes. The agar cubes changed colour from green to red, as shown in Fig. 1.2, in test-tubes A, B and C.
  Step 5 After six minutes the agar cube in test-tube D had not changed colour. The student stopped observing the agar cubes and stopped the stop-clock.
  The times taken for the agar cubes in test-tubes A, B and C to change colour and the time at which the student stopped the stop-clock in step 5 are shown in Fig. 1.3.
  (iii) Convert the times in Fig. 1.3 to seconds.
  Prepare a table and record these results.
  If the time taken is greater than six minutes, record the time as >360 for that cube.
  (iv) State a conclusion for these results.
  (v) Describe the purpose of test-tube D.
  (vi) Identify one safety hazard when carrying out this investigation and describe how the risk of this hazard could be reduced.
  (b) (i) A student calculated the rate of diffusion of acid into an agar cube.
  The student observed that the acid travelled 2mm in 120seconds.
  Suggest how the student could calculate the rate of diffusion.
  (ii) Plan an experiment to investigate the relationship between the size of the agar cubes and the time taken for the agar to change colour.

2. (a) Fig. 2.1 shows a comparison of the nutrient content of beans and nuts.
   A student was given a sample of food and wanted to know if it was from a bean or a nut.
   The student decided to test for the presence of two of the substances listed in Fig. 2.1.
   The results of the tests would enable the student to determine if the food sample was from a bean or a nut.
   Complete Table 2.1 by stating:
   

• which two substances in Fig. 2.1 will enable the student to determine if the food sample is from a bean or a nut
• the food test that would be used to identify each substance
• the positive result for each food test.
  (b) Fig. 2.2 shows the caterpillar of a codling moth. The codling moth damages walnut trees and reduces the yield of the walnut crop.
  To reduce the damage to a walnut crop, scientists released wasps that can kill the codling moth caterpillars. Wasps are flying insects.
  The effect of releasing different numbers of wasps on the damage to a walnut crop was investigated.
  The results are shown in Table 2.2.
  (i) Plot a line graph on the grid of the data in Table 2.2.
  (ii) Describe the pattern shown by the data on your graph.
  (iii) Suggest the number of wasps that should be released into one hectare of walnut trees. State the evidence from your graph that supports your choice.
  (iv) Suggest one way the investigation could be modified to give a more accurate estimate of the optimum (best) number of wasps to release into a walnut crop.
  (c) Fig. 2.3 shows a photograph of a walnut tree leaf.
  (i) Make a large drawing of the leaf shown in Fig. 2.3.
  (ii) Measure the length of line PQ on Fig. 2.3. Include the unit.
  Calculate the actual width of the leaf on Fig. 2.3 using the formula and your measurement.

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