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GCE May 2009 : (A2 3A) Synoptic Paper

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Centre Number 71 Candidate Number ADVANCED General Certificate of Education 2009 Biology assessing Module 6A: Synoptic Paper A2B31 Assessment Unit A2 3A [A2B31] TUESDAY 26 MAY, 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 four questions. INFORMATION FOR CANDIDATES The total mark for this paper is 50. Section A carries 35 marks. Section B carries 15 marks. You should spend approximately 20 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. A data sheet is provided for use with this paper. 4587 For Examiner s use only Question Number 1 2 3 4 Total Marks Marks Section A Examiner Only Marks 1 Remark Throughout much of Britain and Ireland, the introduction of the grey squirrel (Sciurus carolinensis) from North America has led to an increase in its numbers, correlated with a decrease in the numbers of the native red squirrel (S. vulgaris). Red and grey squirrels occupy a similar ecological niche. They are both tree-dwelling mammals that rely on similar food sources (including fruit and nuts). The red squirrel is now confined to isolated pockets of woodland through most of Britain and Ireland. Relative abundance/ arbitrary units The graph shows estimates of population densities of red and grey squirrels in Norfolk, England from 1960 to 1982. 100 red squirrel 80 60 40 20 grey squirrel 0 1960 62 64 66 68 70 72 Year 74 76 78 80 82 (a) Describe the trends shown in the graph. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] (b) Red squirrels are vulnerable to the parapox virus, dying within four days of infection. The virus was found in red squirrel populations prior to the arrival of the grey squirrel, though grey squirrels may aid the spread of the disease, without themselves being affected. How might this information be used to explain the apparent replacement of red squirrels by greys? _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] 4587 2 [Turn over Both the red and the grey squirrel are found in Northern Ireland. A study of habitat associations revealed the results shown in the following table. Red squirrel Grey squirrel Conifer plantations 29 3 Examiner Only Marks Remark Mixed deciduous woodland 13 24 (c) Use the information provided to explain why both species of squirrel are found in N. Ireland. _________________________________________________________ ______________________________________________________ [1] Red squirrels are confined to isolated woodlands in Wales, including those in mid-Wales and the island of Anglesey. DNA analysis of the population in mid-Wales has revealed a significant amount of genetic variability, while the small population on Anglesey has little variability and includes animals with deformities. (d) Explain the importance of genetic variability to a population. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] 4587 3 [Turn over Examiner Only Marks Remark % non-albino grey in population ( 0.50 0.48 85 0.46 0.44 80 0.42 0.40 0.38 75 1976 78 80 82 84 86 88 Year 90 92 0.36 94 1996 proportion albino allele in population ( ) ) Populations of the grey squirrel in its native North America exhibit colour morphs including melanistic (black) forms and albinos. A population of grey squirrels in Illinois, U.S.A. has a surprisingly large frequency of albino forms. A study of this population between 1976 and 1996 revealed results shown in the graph below. (e) Describe the trends evident in the graph and suggest an explanation. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [3] 4587 4 [Turn over BLANK PAGE (Questions continue overleaf) 4587 5 [Turn over 2 In an experiment into the effect of nutrients on the productivity of phytoplankton populations, a series of artificial ponds was created in a lake. Examiner Only Marks Remark Forty ponds were created as follows 10 left untreated as a control 10 enriched with nitrate (NO3 ) 10 enriched with phosphate (PO43 ) 10 enriched with a combination of both nitrate and phosphate. The mean annual productivity for the different groups was measured. Statistical tests were then used to determine the probability that the difference between phytoplankton productivity in the enriched and control groups was due to chance. The results are summarised in the table below. Experimental treatment Mean annual Comparison of treatment productivity/mg mean with control 3 chlorophyll a m t-value p-value year 1 Control 10.33 NO3 enriched 13.98 1.471 PO43 enriched 18.76 2.384 p < 0.05 NO3 & PO43 enriched 25.26 3.986 p < 0.001 (a) Describe the role of nitrate and phosphate in plants. Nitrate __________________________________________________ _________________________________________________________ Phosphate ________________________________________________ _________________________________________________________ [2] 4587 6 [Turn over (b) The p-value for the statistical test comparing the mean phytoplankton productivity for nitrate-enriched ponds and the control ponds is missing in the table. Use the t-value given (and the t-table in the data sheet) to determine the appropriate p-value. Show the appropriate degrees of freedom in the space below, and enter the p-value in the box shaded in the table. Degrees of freedom for the test ______________ Examiner Only Marks Remark [2] (c) Interpret the p-values in the table and evaluate the effect of the nutrients, separately and in combination, on the productivity of the phytoplankton populations. _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [5] (d) Comment on the validity of using the mass of chlorophyll a to estimate the productivity of phytoplankton rather than counting cell numbers. Give one limitation of using chlorophyll a as a measure of phytoplankton abundance. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] 4587 7 [Turn over 3 Read the passage below and then use the information in the passage, and your own understanding, to answer the questions which follow. Many plants contain an array of chemically unrelated compounds which are noxious or toxic, and appear to play a role in restricting the palatibility of the plants in which they occur. Each of these chemicals exhibits a toxic effect on grazing animals by interfering with the normal operation of some physiological process. The effect is often dependent on the concentration of the chemical ingested, and in some cases the chemical, and the plant that produces it, may have a medicinal use in low concentration. Some examples of plants and their toxins are provided below. 5 Individual plants of white clover (Trifolium repens) may contain cyanide. The toxicity of these plants deters grazing by invertebrate herbivores such as slugs, though it does not appear to be effective against large herbivores. Cyanide acts as an inhibitor of the enzyme cytochrome oxidase, in the cristae of the mitochondria of cells, so preventing the transfer of electrons to oxygen. 10 Atropine is contained within the deadly nightshade (Atropa belladonna). In low dosage atropine has been used by ophthalmologists to prevent the constriction of the pupil during the examination of the eye s interior (when a bright light is shone into the eye). Atropine blocks the action of acetylcholine by combining with receptors on the post-synaptic membrane, including neuromuscular junctions. 15 The common foxglove (Digitalis purpurea) contains glycosides collectively called digitalis. Digitalis inhibits the sodium potassium ATPase pump in muscle cells which causes a rise, not only in intracellular sodium ions, but also in intracellular calcium ions which results in greater activation of contractile proteins. At the right dosage, digitalis increases the force of contraction of heart muscle and has been used medically to regulate an irregular heart beat although, with a normal heart and in toxic doses, it leads to cardiac arrest. Aconitine is the toxic component of monkshood (Aconitum napellus). It facilitates the opening of sodium channels in neurones. The overall effect of this opening of sodium channels is to initially cause excitation and repetitive firing of impulses. This eventually gives way to permanent depolarisation, membranes which are then inexcitable and finally paralysis. Aconitine poisoning, again, can result in cardiac arrest. 4587 8 20 25 30 [Turn over (a) As stated in lines 10 and 11, cyanide inhibits cytochrome oxidase. Explain how this leads to the death of an animal which has eaten large quantities of cyanogenic clover. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] (b) Cyanide is stored in vesicles within the cells of cyanogenic white clover. On the other hand, digitalis, aconitine and atropine are all located within the cytoplasm of the plants which produce them. Explain the differences in location of the substances within the plant cell. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] (c) Atropine has been used in low dosage to relieve pain. Explain how atropine would act as a pain reliever. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] (d) Atropine is used before eye examinations to dilate (open) the pupil. Explain how atropine causes the dilation of the pupil [lines 14 and 15]. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] 4587 9 [Turn over (e) Explain how digitalis would cause muscle tissue to contract more strongly [line 22]. Examiner Only Marks Remark _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] (f) Explain how aconitine would ultimately lead to the cessation of neural impulses and so paralysis [line 29]. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] (g) The toxins referred to in the passage all have different effects. Cyanide affects an enzyme, digitalis affects a membrane pump, aconitine affects a membrane channel while atropine affects a membrane receptor. State the type of molecule of which these structures are composed and suggest why toxins may so readily affect the action of this type of molecule. _________________________________________________________ _________________________________________________________ _________________________________________________________ ______________________________________________________ [2] 4587 10 [Turn over Section B Examiner Only Marks Remark You are expected to answer the following question in continuous prose. Diagrams may be used, but you should make sure that they are relevant and add extra information to your account. It will be marked for its biological content, coverage of the topic, and the quality of written communication. In this question up to two marks are awarded for the quality of written communication. [2] 4 Write an account of the uses of ATP in living organisms . Your account should show understanding of at least three topics which you have studied. [13] ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ 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____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ THIS IS THE END OF THE QUESTION PAPER 4587 15 Marks Remark 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. 937-028-1

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Additional Info : Gce Biology May 2009 Assessment Unit A2 3A Module 6A: Synoptic Paper
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