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GCE JAN 2008 : (AS 3) Practical Processes

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education January 2008 Biology assessing Module 3A: Practical Processes ASB31 Assessment Unit AS 3A [ASB31] WEDNESDAY 23 JANUARY, MORNING TIME 1 hour. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. Write your answers in the spaces provided in this question paper. Answer all five questions. You are provided with Photograph 3.2 for use with question 2 in this paper. Do not write your answers on this photograph. INFORMATION FOR CANDIDATES The total mark for this paper is 50. Quality of written communication will be assessed in questions 1(b) and 5(b), (denoted in the paper with an asterisk, *) and awarded a maximum of 2 marks. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. For Examiner s use only Question Number 1 2 3 4 5 QWC Total Marks ASB3AW8 3633 Marks 1 The creeping buttercup (Ranunculus repens) grows in clumps and is common in wet meadows. Examiner Only Marks Remark (a) In an investigation of the distribution of creeping buttercup in a meadow, quadrats were placed at particular sites. The drawing below shows the areas in one quadrat in which creeping buttercup was growing. Wires were used to divide the quadrat into 25 smaller squares. position of creeping buttercup (i) Determine the percentage cover of creeping buttercup in the quadrat. Explain how you arrived at your answer. ______________________________________________________ ______________________________________________________ ____________________________________________________ [2] (ii) Explain why percentage cover is often used to determine the abundance of a plant rather than its frequency. ______________________________________________________ ____________________________________________________ [1] ASB3AW8 3633 2 [Turn over *(b) The meadow in which the investigation took place sloped from a region of dry soil to a lower region of wet soil. Explain how you would investigate whether creeping buttercup is more common in wet or dry regions of the meadow. Examiner Only Marks Remark __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ _______________________________________________________ [4] ASB3AW8 3633 3 [Turn over 2 Photograph 3.2 is a photomicrograph of part of a transverse section through the stem of a sunflower (Helianthus). Examiner Only Marks Remark In the space below, draw a block diagram to show the tissue layers in the stem as shown in the photograph. Label the drawing to identify at least five structures. [9] ASB3AW8 3633 4 [Turn over BLANK PAGE (Questions continue overleaf) ASB3AW8 3633 5 [Turn over 3 The haemocytometer (shown below) was originally developed as a sampling device for counting blood cells, but can also be used to count any cells in a liquid medium. For example, students may use the haemocytometer to count the number of yeast cells in a population and monitor how this changes over time. Surface of slide type-B square (0.04 mm2) type-C square (0.0025 mm2) Central part of slide type-A square (1 mm2) Section of slide showing coverslip in position edge of field of view (low power) Source: Practical Biology for Advanced Level, M. Roberts, T. King, M. Reiss, Nelson, 1994 Examiner Only (a) When carrying out blood counts, the blood sample must be diluted using an isotonic salt (saline) solution rather than water. Suggest why use of an isotonic medium is not as important when working with yeast cells which possess a cell wall. Marks Remark __________________________________________________________ _______________________________________________________ [1] (b) Describe how you would produce an even distribution of yeast cells across the counting grid to enable you to count them. __________________________________________________________ __________________________________________________________ __________________________________________________________ _______________________________________________________ [2] (c) In the older populations of yeast there may be too many yeast cells to allow you to clearly see the grid lines on the slide. Describe how you could treat such populations to enable a count to be made. __________________________________________________________ _______________________________________________________ [1] ASB3AW8 3633 6 [Turn over The diagram below represents four type-C squares from a haemocytometer slide. The distance between the surface of these type-C squares and the overlying coverslip is 0.1 mm. Examiner Only Marks Remark X X (d) (i) Describe how you would select the type-C squares to be counted. ______________________________________________________ ____________________________________________________ [1] (ii) When counting cells, outline the procedure for dealing with those cells lying on or touching the grid lines. ______________________________________________________ ____________________________________________________ [1] (iii) Count the number of yeast cells in the type-C square marked X. ____________________________________________________ [1] (iv) Use your answer from part (iii) to calculate the number of yeast cells per mm3. (Show your working out.) Answer _____________ [2] (e) Describe one way in which the reliability of your yeast population estimate could be improved. __________________________________________________________ _______________________________________________________ [1] ASB3AW8 3633 7 [Turn over 4 Edible periwinkles (Littorina littorea) are common marine molluscs found on rocky shores. When the tide is out the periwinkles withdraw into their shells to prevent drying out. When immersed in seawater the periwinkle will partially emerge from its shell and move about grazing on algae. The body fluids of the animal have the same water potential ( ) as seawater. Examiner Only Marks Remark In an experiment on the responses of periwinkles to different osmotic situations, groups of 30 periwinkles were immersed in varying dilutions of seawater. In each situation the number of periwinkles that had withdrawn into their shells after 10 minutes was recorded. The results are shown in the table below. Percentage of seawater in the immersing 100 90 solution/% [seawater] 80 70 65 60 50 40 Number of periwinkles withdrawn into shells 0 4 8 13 23 30 1 0 (a) Plot the above results, using an appropriate graphical technique. (Use the graph paper opposite.) [6] (b) With reference to water potential, explain what happens osmotically when periwinkles are placed in diluted seawater. __________________________________________________________ __________________________________________________________ _______________________________________________________ [2] (c) Describe the trend illustrated in the graph. __________________________________________________________ __________________________________________________________ _______________________________________________________ [2] (d) Suggest why the periwinkles have withdrawn into their shells when immersed in 40% seawater. __________________________________________________________ __________________________________________________________ _______________________________________________________ [2] ASB3AW8 3633 8 [Turn over ASB3AW8 3633 9 [Turn over 5 The breakdown of hydrogen peroxide to water and oxygen is catalysed by the enzyme catalase. This enzyme is present in all living tissues, as hydrogen peroxide is a toxic by-product of metabolism. Catalase activity can be detected in the laboratory by the amount of foam produced from the production of oxygen, when it reacts with hydrogen peroxide. This can be measured in a measuring cylinder as shown below. Examiner Only Marks Remark foam (oxygen bubbles) mixture of catalase and hydrogen peroxide You are asked to devise a plan to investigate the effect of concentration of hydrogen peroxide on the activity of catalase in liver tissue. You are supplied with liver standard hydrogen peroxide solution distilled water measuring cylinders and general laboratory apparatus (a) State the ASB3AW8 independent variable ______________________________________ dependent variable 3633 ____________________________________ [2] 10 [Turn over *(b) Describe your plan for carrying out the investigation. Examiner Only Marks Remark __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ __________________________________________________________ _______________________________________________________ [4] (c) Suggest two possible limitations in your method. 1. _______________________________________________________ __________________________________________________________ 2. _______________________________________________________ _______________________________________________________ [2] (d) Using the axes below, show how you would present the results graphically. Label the axes appropriately and, on the basis of your understanding of enzyme action, draw a graph of the results that you would expect. [2] Quality of written communication ASB3AW8 3633 11 [Turn over Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright holders may have been unsuccessful and CCEA will be happy to rectify any omissions of acknowledgement in future if notified. S SB3AW8302-029-1 A 3/07 3633 12 [Turn over GCE Biology Advanced Subsidiary (AS) Assessment Unit AS 3A Module 3A: Practical Processes January 2008 Photograph 3.2 Source: Chuck Brown/Science Photo Library ASB3AW8 3633.02 ASB31IN1 (For use with Question 2)

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Additional Info : Gce Biology January 2008 Assessment Unit AS 3 Module 3A: Practical Processes
Tags : General Certificate of Education, A Level and AS Level, uk, council for the curriculum examinations and assessment, gce exam papers, gce a level and as level exam papers , gce past questions and answer, gce past question papers, ccea gce past papers, gce ccea past papers

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