Question 126 marks
Question
You are going to investigate the effect of temperature on the movement of water in celery stalks using a coloured dye. In plant stems such as a celery stalk, water moves in the xylem tissue within the vascular bundles. Read all the instructions but DO NOT DO THEM until you have drawn a table for your results in the space provided in 1(a)(ii). You should use the safety equipment provided while you are doing the practical work. Step 1 You will use beakers C and W as water‑baths in this investigation. Raise your hand when you are ready for warm water to be added to beaker W. Step 2 Carefully lower one of the small beakers of dye into beaker C and the other small beaker of dye into beaker W, as shown in Fig. 1.1. large beaker C large beaker W containing ice-cold containing warm water water small beaker small beaker containing dye containing dye Fig. 1.1 Step 3 To let the dye equilibrate in the water‑baths, wait for five minutes before you continue to step 4. While you are waiting, measure the temperatures of the water in large beaker C and large beaker W. Record these starting temperatures in Table 1.1 in 1(a)(i). (a) (i) Table 1.1 large beaker starting temperature of the water / °C final temperature of the water / °C C …… …… W …… …… [1] Step 4 Put one celery stalk into each small beaker of dye, as shown in Fig. 1.2. Leave the celery stalks in the dye for three minutes. * 0000800000003 * DFD 3 celery stalk large beaker C or W dye not to scale Fig. 1.2 Step 5 While you are waiting, draw a line down the middle of the white tile, label one half C and the other half W. Step 6 After three minutes, remove the celery stalk from the dye in beaker C and put it on the part of the white tile labelled C. Remove the celery stalk from the dye in beaker W and place it on the part of the white tile labelled W. Use a paper towel to remove any excess dye. Step 7 On the part of the white tile labelled C cut a section across the celery stalk 5 mm from the end that was in the dye, as shown in Fig. 1.3. end of the celery stalk that was in the dye cut across the celery stalk to form a 5 mm wide section not to scale Fig. 1.3 * 0000800000004 * DFD 4 Step 8 Examine the xylem tissue of the cut section of celery stalk to see if the 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 9 If the dye is still visible in the celery stalk cut another 5 mm wide section from the celery stalk. Continue cutting 5 mm wide sections from the celery stalk until the dye is no longer visible. Step 10 Count the number of sections you have cut that contain the dye. Record this number in your table in 1(a)(ii). Step 11 Repeat steps 7 to 10 with the other celery stalk on the part of the white tile labelled W. Step 12 Measure the final temperatures of the water in large beaker C and large beaker W and record these temperatures in Table 1.1 in 1(a)(i). (ii) Prepare a table and record your results. Include the number of sections cut and the total distance moved by the coloured dye in each celery stalk. [5] * 0000800000005 * DFD 5 (iii) Calculate the rate of movement of the 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] * 0000800000006 * DFD 6 (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] (ii) In step 9, it is difficult to determine precisely the final position of the dye in the xylem. Suggest an improvement to the method that would reduce this source of error. …… [1] * 0000800000007 * DFD 7 * 0000800000008 * DFD 8 (d) 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. 1.5 is a photograph of a black aphid. A B magnification ×35 Fig. 1.5 Fig. 1.6 is a photograph of a leaf miner fly. magnification ×11 Fig. 1.6 * 0000800000009 * DFD 9 (i) Line AB represents the body length of the black aphid. Measure the length of line AB in Fig. 1.5. 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. 1.5 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. 1.6 differs from the black aphid shown in Fig. 1.5. 1 …… 2 …… 3 …… [3] * 0000800000010 * DFD 10 (e) Fig. 1.7 is a photograph of a celery leaf. Fig. 1.7 Draw a large diagram of the celery leaf shown in Fig. 1.7. [4] * 0000800000011 * DFD 11 (f) Carbon dioxide moves into celery leaves for photosynthesis. State the name of an indicator which could be used to test for the presence of carbon dioxide gas. …… [1] [Total: 26] * 0000800000012 * DFD 12
Mark scheme
1(a)(i) four temperatures recorded ; 1 1(a)(ii) table drawn with the correct number of columns and a header line ; 5 e.g. appropriate column / row headings, with units for distance ; number total recording of the number of sections for both C and W ; temperature of distance recording of the total distances for both C and W ; sections / mm correct trend – i.e. distance in W greater than in C ; cold / C warm / W 1(a)(iii) correct value that matches the candidate’s results ; 2 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 the same dye OR type / colour of dye ; time to equilibrate ; length of time in the dye ; width of sections ; AVP ; 1c)(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 or thinner sections ; 1 A If the dye reached the end of the stalk, increase the length of time celery is left in dye ; increase the length of the stalk or decrease the time in the dye. 1(d)(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(d)(ii) any three differences from: 3 one mark per correct row leaf miner fly / Fig. 1.6 black aphid / Fig. 1.5 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(e) 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 ; 1(f) limewater ; 1