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GCE JAN 2011 : (A2 1) Physiology and Ecosystems - Revised

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education January 2011 Biology assessing Physiology and Ecosystems AB211 Assessment Unit A2 1 [AB211] MONDAY 24 JANUARY, AFTERNOON TIME 2 hours. 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 nine questions. You are provided with Photograph 4.5 for use with Question 5 in this paper. Do not write your answers on this photograph. INFORMATION FOR CANDIDATES 111608 The total mark for this paper is 90. Section A carries 72 marks. Section B carries 18 marks. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. You are reminded of the need for good English and clear presentation in your answers. Use accurate scientific terminology in all answers. You should spend approximately 25 minutes on Section B. You are expected to answer Section B in continuous prose. Quality of written communication will be assessed in Section B and awarded a maximum of 2 marks. 6948.11R For Examiner s use only Question Marks Number 1 2 3 4 5 6 7 8 9 Total Marks Section A Examiner Only Marks 1 Remark Read the following passage about the development of a community over a period of time and write the most appropriate word(s) in the blank spaces to complete the account. The initial colonisation of bare rock is by __________________ species. Over time as the soil develops, more species colonise the area, a process known as __________________ succession. The final stable community is known as the __________________ community. If this final community is destroyed by fire a more rapid __________________ succession may take place. [4] 6948.11R 2 [Turn over 2 (a) Auxins and gibberellins are both plant growth substances which promote cell elongation in different parts of the stem. State which parts of the plant stem are stimulated by Auxins Examiner Only Marks Remark ____________________________________ Gibberellins ________________________________ [1] (b) Growth in plants involves the division of cells which subsequently increase in length. In an experiment, the effects of two growth substances on both cell division and cell elongation were compared with an untreated control plant. Each treatment resulted in longer stems than the untreated control. The specific effects on cell division and cell elongation are shown in the table below. Treatment with an artificial growth substance Untreated Control 1-naphthaleneacetic acid (NAA) 2,4-dichlorophenoxyacetic acid (2,4-D) Cell division average number of new cells produced /cells day 1 3.9 3.8 5.9 Cell elongation average increased length of each new cell/ m 30 48 24 Using the information in the table, explain the increase in stem elongation produced by each treatment. Examiner Only Marks Remark _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ ___________________________________________________________ [3] 6948.11R 3 [Turn over 3 Almost all drugs taken by humans, including nicotine and alcohol, affect the nervous system, especially synapses. Examiner Only Marks Remark (a) The drug nicotine, found in the leaves of the tobacco plant, binds to the acetylcholine receptor sites in synapses. After binding to these receptor sites, nicotine acts in a similar way to acetylcholine. (i) Using your understanding of the nerve synapse, describe precisely where nicotine would bind. _______________________________________________________ [1] (ii) Describe and explain the effect of nicotine on the nervous system. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (iii) Unlike acetylcholine, nicotine is not broken down within the synapse. Suggest one possible consequence of nicotine remaining in the synapse. _________________________________________________________ _______________________________________________________ [1] 6948.11R 4 [Turn over (b) The drug alcohol, binds with gamma aminobutyric acid (GABA) receptors in synapses. After binding, alcohol acts in a similar way to GABA the inside of the neurone membrane becomes more negative, a state known as hyperpolarisation. Examiner Only Marks Remark (i) Suggest one way in which alcohol causes the inside of the membrane to become more negative. _________________________________________________________ _______________________________________________________ [1] (ii) Alcohol is known to inhibit the nervous system. Suggest how this inhibition may be brought about. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (iii) Suggest one consequence of alcohol inhibition of the nervous system. _________________________________________________________ _______________________________________________________ [1] 6948.11R 5 [Turn over 4 During photosynthesis by green plants, light energy is converted into chemical energy, some of which is subsequently used in respiration. Examiner Only Marks Remark (a) The diagram below shows the fate of incident light energy on 1 m2 of grass. (Units kJ m 2 y 1.) Total incident light energy 1.0 106 Heat used in evaporation from the soil and during transpiration 5.0 105 Reflected light energy 1.6 105 Light energy passing through the grass 3.2 105 Chemical energy from photosynthesis 2.0 104 Plant respiration 2.0 103 (i) Calculate the percentage of the total incident light energy which is converted into chemical energy. Show your working. Answer _______________________ [2] (ii) Define the term Net Primary Production (NPP). _________________________________________________________ _______________________________________________________ [1] (iii) Calculate NPP for the grass. Answer _______________________ [1] 6948.11R 6 [Turn over (b) The processes of photosynthesis and respiration are both influenced by temperature. The graph below shows NPP of grass at different temperatures. 60 40 NPP/arbitrary units 20 0 0 5 10 15 20 25 30 35 40 20 40 Temperature/ C (i) Explain the negative NPP values above 30 C. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (ii) Early summer temperatures are in the range 5 to 20 C. Explain why grass is a suitable species for cropping as silage in early summer. _________________________________________________________ _______________________________________________________ [1] (c) Explain two advantages of using silage to feed cattle over allowing the cattle to graze the field. 1. ___________________________________________________________ _____________________________________________________________ 2. ___________________________________________________________ ___________________________________________________________ [2] 6948.11R 7 [Turn over 5 The growth of maize in Ireland has been improved by the introduction of photodegradable plastic. The photographs 4.5 X and Y show photodegradable plastic strips with maize seedlings growing through perforations in the plastic. Examiner Only Marks Remark (a) Suggest one advantage of the plastic being photodegradable. _____________________________________________________________ ___________________________________________________________ [1] (b) The plastic strip influences the temperature of the soil underneath. The table below shows the average soil temperatures for May and June underneath a plastic strip (at the centre and at its edge) and in soil lacking plastic cover. Soil temperature/ C Month Under plastic cover No plastic cover Centre Edge May 14.9 13.0 11.4 June 19.9 17.7 16.0 (i) Using the information in the table, explain why the use of plastic strips improves the growth of maize. _________________________________________________________ _________________________________________________________ _______________________________________________________ [1] (ii) Examine photographs 4.5 X and Y and suggest two additional advantages of growing maize under plastic. 1. _______________________________________________________ _________________________________________________________ 2. _______________________________________________________ _______________________________________________________ [2] 6948.11R 8 [Turn over (c) The growth of maize under plastic was investigated at two sites in Ireland: Carrick-on-Suir, Co. Tipperary (in the South-East) and Dromore, Co Down (in the North-East). Five varieties of maize were tested. The table below shows the relative performance of the varieties at the two sites. (100 represents the overall average for the five varieties at both sites.) Carrick-on-Suir Grain yield Grain yield Nancis 102 125 Loft 104 123 Hudson 117 102 Rival 111 58 Janna 108 Remark Dromore Variety Examiner Only Marks 50 Comment on the influence of the site on the relative performance of the varieties in the investigation. _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ ___________________________________________________________ [3] 6948.11R 9 [Turn over (d) In recent years, maize silage has become a significant component of the feed on many dairy and beef farms in Ireland. Examiner Only Marks Remark In an investigation into the benefits of feeding cattle with a grassmaize silage mixture compared to grass-only silage, the weight of the finished beef cattle was found to be greater when maize was included in their diet. The table below shows other comparisons made during the investigation. Grass silage Grass plus maize silage Mean amount eaten /kg dry matter day 1 8.38 9.08 Energy absorbed/MJ day 1 104 111 Energy stored in the carcass/MJ day 1 5.0 5.9 (i) Using the information in the table, explain the increased weight of cattle fed on the grass-maize silage. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (ii) Suggest two reasons why so little of the absorbed energy is stored in the carcass. 1. _______________________________________________________ _________________________________________________________ 2. _______________________________________________________ _______________________________________________________ [2] 6948.11R 10 [Turn over BLANK PAGE (Questions continue overleaf) 6948.11R 11 [Turn over 6 In humans, the process of osmoregulation is an example of homeostasis and involves the release of antidiuretic hormone (ADH) which controls water loss a thirst response which controls water uptake through drinking The graphs below show how ADH levels and the intensity of a person s thirst are affected by changing plasma solute concentration. Graph A Graph B 20 10 16 8 Plasma ADH 12 /pmol dm 3 8 Intensity of thirst /arbitrary units 4 0 6 4 2 0 280 290 300 310 320 Plasma solute concentration /mOsmol kg 1 280 290 300 310 320 Plasma solute concentration /mOsmol kg 1 (a) Using the information in Graph A and your understanding of how ADH is released into the plasma, explain the effect of changing plasma solute concentration on plasma ADH levels. Examiner Only Marks Remark _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ ___________________________________________________________ [4] 6948.11R 12 [Turn over (b) Describe and explain the effect of increasing ADH levels on urine production. Examiner Only Marks Remark _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ ___________________________________________________________ [3] (c) With reference to Graph B, describe and explain the relationship between a person s thirst and the plasma solute concentration. _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ ___________________________________________________________ [2] (d) Plan an investigation which tests the following hypothesis. Drinking isotonic solutions instead of water reduces urine production (There is no need to include a plan for statistical analysis.) _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ ___________________________________________________________ [4] 6948.11R 13 [Turn over 7 (a) The diagram below summarises part of the nitrogen cycle. Examiner Only Marks Remark atmospheric nitrogen A B nitrates in soil C plant protein ammonium compounds Identify the processes labelled A to C. A ______________________________________ B ______________________________________ C ______________________________________ [3] (b) Nitrogen-containing compounds can be added to soil by the use of artificial fertilisers. There are both economic and environmental reasons for determining the amount of artificial fertiliser to add to cereal crops, such as wheat. Yield of wheat grain/t ha 1 An investigation was carried out to determine the effect of adding different levels of artificial fertiliser on the amount of wheat grain harvested. The results are shown in the graph below. 9 8 7 6 5 4 3 2 1 0 0 50 100 150 Applied nitrogen/kg ha 1 200 Source: Plant science in action. Caroline Barnes and Nick Poore. Hodder and Stoughton ISBN 0-340-60099-3 6948.11R 14 [Turn over Describe and explain the results of the investigation. Examiner Only Marks Remark _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ ___________________________________________________________ [4] (c) Nitrates are very soluble and are easily leached from soil, causing eutrophication in local rivers. Explain how eutrophication causes a high Biological Oxygen Demand (BOD) in a river. _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ _____________________________________________________________ ___________________________________________________________ [3] 6948.11R 15 [Turn over 8 Reindeer (Rangifer tarandus) have been introduced to remote oceanic islands to provide a source of meat for sailors on whaling ships. Examiner Only Marks Remark (a) On South Georgia, in the South Atlantic Ocean, reindeer were first introduced in 1909. The reindeer graze the lowland grass community of plants when this is not covered by winter snow. In the winter months the deer graze the lichen-rich banks, where less snow accumulates. The table shows the plant species present in the lichen-rich banks for an area where there are no reindeer (ungrazed) and where reindeer are present (grazed). Mean percentage cover/% Plant species Area ungrazed by reindeer Area grazed by reindeer Vascular plants Acaena decumbens Acaena tenera Festuca erecta Phleum alpinum Rostkovia magellanica 9 4 17 7.5 5 5 40 Lichens Cetraria islandica Cladonia balfourii Cladonia carneola Cladonia furcata Cladonia rangiferina Ochrolechia frigida Pseudocyphellaria freycinetii Psoroma hypnorum Stereocaulon glabrum 10 4 6 10 5 23 5 5 2 1 2 5 3 21.5 20.5 4 40 40 Mosses Chorisodontium aciphyllum Polytrichum alpinum Tortula robusta 6948.11R 16 [Turn over (i) Comment on the effect of grazing on the diversity of the plant species. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] (ii) It has been suggested that the reindeer population should be totally removed from the island. The killing of reindeer on South Georgia is controversial. Suggest the arguments that biologists might present to justify the killing of the reindeer population. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [3] 6948.11R 17 [Turn over (b) A reindeer population was introduced to St Matthew Island in the North Pacific. The climate, with heavy winter snow falls, and the vegetation cover on St Matthew is very similar to that of South Georgia. Examiner Only Marks Remark A biologist undertook censuses of the reindeer population on the island in certain years. These showed a huge increase followed by a rapid decline: 29 deer in 1944; 1 350 in 1957; 6 000 in 1963; and finally only 42 in 1964. These population numbers are shown in the graph below. The dotted line is the biologist s assumption of the growth curve overall. 7 6 Population size/thousands 5 4 3 2 1 1940 1950 Time/year 1960 Source: David R Klein The introduction, increase, and crash of reindeer on St Matthew Island Alaska Cooperative Wildlife Research Unit, University of Alaska 6948.11R 18 [Turn over (i) Suggest why the biologist chose an exponential curve to represent the growth of the reindeer population up to 1963. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (ii) During the winter of 1963 64 exceptionally high levels of snow occurred. Suggest how the study in South Georgia, described in part (a), may explain the huge decline in the St Matthew population from 1963 to 1964. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] (iii) Suggest why these boom and bust population changes do not occur in reindeer populations on the mainland. _________________________________________________________ _________________________________________________________ _________________________________________________________ _______________________________________________________ [2] 6948.11R 19 [Turn over Section B Examiner Only Marks 9 Remark Quality of written communication is awarded a maximum of 2 marks in this section. [2] Give an account of the various immune responses following the entry of bacteria and viruses into the blood at the site of a wound. [16] _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ 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_________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ 6948.11R 24 [Turn over THIS IS THE END OF THE QUESTION PAPER 6948.11R 25 [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. 111608R GCE Biology Advanced (A2) Assessment Unit A2 1: Physiology and Ecosystems January 2011 Photographs 4.5 X and Y (for use with question 5) Metre wide sheets of photodegradable plastic with maize plants emerging through the perforated plastic Source: Chief Examiner 6948.02 111609

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Additional Info : Gce Biology January 2011 Assessment Unit A2 1 Physiology and Ecosystems - Revised
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