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GCE JAN 2007 : (AS 2) Physiology and Ecology

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Centre Number 71 Candidate Number ADVANCED SUBSIDIARY (AS) General Certificate of Education January 2007 Biology assessing Module 2: Physiology and Ecology ASB21 Assessment Unit AS 2 [ASB21] TUESDAY 16 JANUARY, AFTERNOON 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 eight questions. INFORMATION FOR CANDIDATES The total mark for this paper is 55. Section A carries 43 marks. Section B carries 12 marks. You should spend approximately 15 minutes on Section B. You are expected to answer Section B in continuous prose. Quality of written communication will be assessed in Section B. 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 6 7 8 Total Marks ASB2W7 2477 Marks Section A 1 Examiner Only Marks Remark Any one of three environmental factors may directly limit the rate at which photosynthesis takes place in plants. Which factor would you expect to limit the rate of photosynthesis in each of the following conditions? (a) A field of wheat on a sunny day in summer. _______________________________________________________ [1] (b) A field of grass in winter. _______________________________________________________ [1] (c) The herb layer on a woodland floor in summer. _______________________________________________________ [1] ASB2W7 2477 2 [Turn over 2 The diagram below summarises the sequence of events which lead to the formation of a blood clot. Examiner Only Marks Remark Platelet breakdown and tissue damage Fibrinogen P Prothrombin Thrombin Q (an ion) R (a) Identify P, Q and R. P ________________________________ Q ________________________________ R ________________________________ [3] (b) Which vitamin is required for the synthesis of prothrombin in the liver? _______________________________________________________ [1] (c) A clot may sometimes occur in the coronary artery resulting in a myocardial infarction (heart attack). Describe the events which may occur within the coronary artery to induce blood clotting. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] ASB2W7 2477 3 [Turn over 3 (a) Describe two features of a xylem vessel that help it to carry out the function of water transport in plants. Examiner Only Marks Remark 1. _______________________________________________________ _________________________________________________________ 2. _______________________________________________________ _______________________________________________________ [2] (b) Explain how water moves through xylem vessels according to the cohesion tension theory. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [4] ASB2W7 2477 4 [Turn over 4 The botanist, Palmblad, carried out an investigation into the effect of competition in the Canadian fleabane plant (Conyza canadensis). Examiner Only Marks Remark In 4 moist, compost-filled pots, he placed 1, 5, 50 and 200 fleabane seeds respectively. After 4 days the number of plants germinated and the mean dry mass of the plants produced in each pot was recorded. The table below illustrates the results. Number of seeds per pot 1 5 50 200 % germination 100 87 56 52 Mean dry mass per plant/g 12.7 3.5 0.355 0.092 Source: Modified from New Perspectives in Advanced Biology. Martin Hanson. Hodder and Stoughton, 1999. (a) Describe two trends in the data shown in the table. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (b) Suggest one possible explanation for the trends you have described. _________________________________________________________ _______________________________________________________ [1] (c) Calculate the total dry mass of the plants which germinated in the pot in which 50 seeds were planted. Answer _________________ [2] ASB2W7 2477 5 [Turn over 5 The diagram below shows a section through alveoli and associated structures in the lung. Examiner Only Marks Remark Epithelial cell which produces surfactant Alveolus Epithelial cells Blood capillary Blood capillary Red blood cell Endothelial cell Source: Adapted from Biology Principles and Processes, Roberts, Reiss and Monger, Nelson, 1993. (a) The diffusion of oxygen from the alveoli into the blood complies with Fick s Law. This states that the rate of diffusion is directly proportional to the concentration gradient. greater when the diffusion distance is short. A third factor is also involved. (i) Describe how the concentration gradient of oxygen is maintained between the alveolus and the blood in the capillary. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) Name the type of flattened epithelial cells found lining the alveoli. ___________________________________________________ [1] ASB2W7 2477 6 [Turn over (iii) Suggest the third factor that would influence the rate of diffusion in Fick s law, and describe how this is provided within the lung. Examiner Only Marks Remark _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (b) Explain the role of surfactant in the alveolus. _________________________________________________________ _______________________________________________________ [1] ASB2W7 2477 7 [Turn over 6 The diagram shows the energy flow through a grassland ecosystem. The size of boxes and arrows are not to scale. The units are kJ m 2 y 1. Examiner Only Marks Remark total insolation: 7.1 106 light absorbed by plants: 1.71 106 Gross Primary Production (energy trapped in glucose) = 87 403 87403 producer biomass food 14 147 50 303 9 heat loss in respiration 87 403 primary consumer biomass 99 45 793 22 953 food 1609 1328 193 2nd consumers 88 55 33 3rd consumers detritus 27 778 decomposers 27 778 Source: Adapted from Ecology, T. J. King, Nelson, 1980. Use the information in the diagram to answer the following questions. (a) Calculate the Net Primary Production in this ecosystem. _______________________________________________________ [1] (b) What is the major destination of the energy available to the ecosystem as Net Primary Production? Calculate the percentage of the Net Primary Production passing along this route. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] ASB2W7 2477 8 [Turn over (c) It is often assumed that the energy taken in by animals at one trophic level is about 10% of the energy taken in by animals at the previous trophic level. Does this generalisation apply to the energy transfer between the primary consumers and the secondary consumers in this ecosystem? Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (d) Why is there no fourth consumer level in this ecosystem? _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (e) Over the whole year the energy leaving this grassland ecosystem equals the energy entering it (87 403 kJ m 2). Suggest why, in a woodland ecosystem, less energy may leave than enter it. _________________________________________________________ _________________________________________________________ _______________________________________________________ [1] ASB2W7 2477 9 [Turn over 7 The graph below shows the oxygen dissociation curve for human haemoglobin andExaminer Only llama Marks haemoglobin. The llama lives in the high Andes of South America, often above 5 000 m.Remark 100 90 Llama haemoglobin 80 Saturation with oxygen/% Human haemoglobin 70 60 50 40 30 20 10 0 0 2 4 6 8 10 12 14 Partial pressure of oxygen/kPa Examiner Only Marks Remark (a) With reference to the curve for human haemoglobin, and your own understanding, explain how haemoglobin (i) takes up oxygen in the lungs; _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] (ii) gives up oxygen to the tissues. _____________________________________________________ _____________________________________________________ _____________________________________________________ ___________________________________________________ [2] ASB2W7 2477 10 [Turn over (b) The loading tension is the partial tension of oxygen at which 95% of the haemoglobin is saturated with oxygen. Examiner Only Marks Remark From the graph, determine the loading tensions for human and llama haemoglobin. Human haemoglobin ___________________ Llama haemoglobin ____________________ [2] (c) Explain how the oxygen dissociation curve for the llama haemoglobin differs from that for a human, and why this is an important adaptation in the llama. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] ASB2W7 2477 11 [Turn over Section B Examiner Only Marks Remark In this section you are expected to answer in continuous prose, supported, where appropriate, by diagrams. You are reminded that up to two marks in this question are awarded for the quality of written communication. [2] 8 Give an account of the adaptations and roles of the following blood vessels in the mammalian circulatory system. Arteries Capillaries Veins [10] Arteries ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ASB2W7 2477 12 [Turn over Capillaries Examiner Only Marks Remark ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ Veins ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ASB2W7 2477 13 [Turn over THIS IS THE END OF THE QUESTION PAPER 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 SB2W7 2477 A 03/06 2100 9-024-1 [Turn6over 1 [Turn over

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Additional Info : Gce Biology January 2007 Assessment Unit AS 2 Module 2: Physiology and Ecology
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