Question 126 marks
Question
A student investigated the effect of temperature on the movement of water in celery stalks. The water contained a blue dye. In plant stems such as a celery stalk, water moves in the xylem tissue within the vascular bundles. The student used this method: Step 1 Take two stalks of celery and cut them so that they are both 10 cm long. Step 2 Prepare an ice-cold water-bath C and a warm water-bath W. Place a beaker of blue dye into each water-bath, as shown in Fig. 1.1. large large beaker C beaker W containing containing ice-cold warm water water blue dye blue dye Fig. 1.1 Step 3 Measure the temperatures of the water in water-bath C and water-bath W. Step 4 Let the blue dye equilibrate in the water-baths for three minutes. Step 5 After three minutes, place one celery stalk into each beaker of blue dye, as shown in Fig. 1.2. Keep the celery stalks in the blue dye for ten minutes. 10 cm long celery stalk water-bath blue dye not to scale Fig. 1.2 Step 6 After ten minutes, measure the final temperatures of the water in water-bath C and water-bath W. * 0000800000003 * DFD 3 (a) (i) Complete Table 1.1 by calculating the change in the water temperature for each water-bath. Table 1.1 water temperature water temperature change in water temperature water-bath in step 3 / °C in step 6 / °C / °C C 4 15 …… W 40 28 …… [1] Step 7 Remove the celery stalk from the blue dye in water-bath C and put it on a white tile. Step 8 Cut a section across the celery stalk 5 mm from the end that was in the blue dye, as shown in Fig. 1.3. end of the celery stalk that was in the blue dye cut across the celery stalk to form a 5 mm wide section not to scale Fig. 1.3 Step 9 Examine the xylem tissue of the cut section of celery stalk to see if the blue dye is visible. Fig. 1.4 shows the position of the xylem tissue in a cut section of a celery stalk. position of the xylem Fig. 1.4 Step 10 If the blue dye is still visible in the celery stalk, cut another 5 mm wide section from the dyed end of the remaining part of the celery stalk. Continue cutting 5 mm wide sections from the celery stalk until the blue dye is no longer visible in the cut section. Step 11 Count the number of sections you have cut from the celery stalk that contain the blue dye. Step 12 Repeat steps 7 to 11 with the celery stalk from water-bath W. * 0000800000004 * DFD 4 The student’s results are shown in Fig. 1.5. number of 5 mm wide sections cut from the celery stalk in C = 4 number of 5 mm wide sections cut from the celery stalk in W = 13 Fig. 1.5 (ii) Prepare a table and record the results shown in Fig. 1.5. Include the number of sections cut and the total distance moved by the blue dye in each celery stalk. [4] * 0000800000005 * DFD 5 (iii) Calculate the rate of movement of the blue dye in the celery stalk in beaker W. Include the unit. …… [2] (iv) State a conclusion for this investigation. …… [1] (v) This investigation was only done once. Explain why it is better to repeat an investigation. …… [1] (b) Identify two variables that were kept constant in this investigation. 1 …… 2 …… [2] (c) (i) The data you have recorded in Table 1.1 may indicate that there is a source of error with the method used in this investigation. Identify the possible error, and describe an improvement to the method to reduce the effect of this error. error …… improvement …… [2] * 0000800000006 * DFD 6 (ii) In step 9, it is difficult to determine precisely the final position of the blue dye in the xylem. Suggest an improvement to the method that would reduce this source of error. …… [1] (d) Xylem forms cylinder-like structures in a celery stalk. Calculate the volume of a cylinder which is 100 mm long and has a diameter of 0.06 mm. Use this formula: v = π r2 h Use a value for π of 3.14. Give your answer to two decimal places. Space for working. …… mm3 [2] * 0000800000007 * DFD 7 * 0000800000008 * DFD 8 (e) Celery plants can be damaged by insect pests feeding on them. This can reduce the growth of the celery plants. A black aphid and the larvae of a leaf miner fly are both insect pests that damage celery plants. Fig. 1.6 is a photograph of a black aphid. A B magnification ×35 Fig. 1.6 Fig. 1.7 is a photograph of a leaf miner fly. magnification ×11 Fig. 1.7 * 0000800000009 * DFD 9 (i) Line AB represents the body length of the black aphid. Measure the length of line AB in Fig. 1.6. length of line AB …… mm Calculate the actual body length of the black aphid using the formula and your measurement. length of line AB in Fig. 1.6 magnification = actual body length of the black aphid Give your answer to one significant figure. Space for working. …… mm [3] (ii) State three ways that the leaf miner fly shown in Fig. 1.7 differs from the black aphid shown in Fig. 1.6. 1 …… 2 …… 3 …… [3] * 0000800000010 * DFD 10 (f) Fig. 1.8 is a photograph of a celery leaf. Fig. 1.8 Draw a large diagram of the celery leaf shown in Fig. 1.8. [4] [Total: 26] * 0000800000011 * DFD 11
Mark scheme
1(a)(i) C = 11 and W = 12 ; 1 1(a)(ii) table drawn with correct number of columns and a header line ; 4 e.g. appropriate column / row headings, with units for distance ; number total recording of correct number of sections for both C and W ; temperature of distance recording of correct total distances for both C and W ; sections / mm cold / C 4 20 warm / W 13 65 1(a)(iii) 6.5 ; 2 ecf from 1(a)(ii) mm per minute ; 1(a)(iv) the higher the temperature the greater the (rate of) dye / water movement ; 1 ecf from 1(a)(ii) 1(a)(v) to identify, anomalous results / outliers / results that do not follow the trend ; 1 1(b) any two from: 2 both used celery OR same, species / type, of plant ; length of celery (stalk) ; both used blue dye OR type / colour of dye ; time to equilibrate ; length of time in the dye ; width of sections ; 1(c)(i) error from Table 1.1 2 temperature (of the water-bath) not controlled / AW ; improvement thermostatically controlled water–bath ; 1(c)(ii) cut smaller / thinner sections OR cut the celery vertically / longitudinally ; 1 1(d) 0.28 (mm3) ; 2 MP1 correct calculation to any number of decimal places MP2 correct rounding to two decimal places ecf from previous MP 1(e)(i) line AB = 60 ±1 (mm) ; 3 MP1 correct measurement of line AB 2 (mm) ;; MP2 correct calculation of actual size to any number of significant figures MP3 correct rounding to one significant figure 1(e)(ii) any three differences from: 3 one mark per correct row leaf miner fly / Fig. 1.7 black aphid / Fig. 1.6 1 larger OR smaller 2 shorter antennae / AW OR longer antennae / AW 3 has wings AND no wings 4 hairs on body AND no hairs on body 5 larger eye OR smaller eye 6 lack of two projections AND two projections / AW / AW, sticking out of sticking out of abdomen / back abdomen / back 7 shorter legs OR longer legs 8 thicker legs OR thinner legs 9 only three legs (visible) AND six legs 10 larger head OR smaller head ;;; 1(f) single clear outline with no shading ; 4 drawing larger than half the available space ; detail 1: deep V-shaped cleft correctly located on the upper right third of the leaf ; detail 2: between three and five separate veins coming from the same level at the top of the petiole ;