Final Marking Guidelines 2011 examination June series. Biology Unit 6T A2 Investigative Skills Assignment. General Certificate of Education

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1 Genera Certificate of Education Bioogy Unit 6T A2 Investigative Skis Assignment BIO6T/Q11/MG Fina Marking Guideines 2011 examination June series WMP/Jun11/BIO6T/Q11/MG

2 2 Marking Guideines are prepared by the Principa Moderator and considered, together with the reevant questions, by a pane of subject teachers. Copyright 2011 AQA and its icensors. A rights reserved. COPYRIGHT AQA retains the copyright on a its pubications. However, registered centres for AQA are permitted to copy materia from this booket for their own interna use, with the foowing important exception: AQA cannot give permission to centres to photocopy any materia that is acknowedged to a third party even for interna use within the centre. Set and pubished by the Assessment and Quaifications Aiance. The Assessment and Quaifications Aiance (AQA) is a company imited by guarantee registered in Engand and Waes (company number ) and a registered charity (registered charity number ). Registered address: AQA, Devas Street, Manchester M15 6EX.

3 3 Guidance for teachers marking Bioogy ISAs Fina Marking Guideines must be used to mark candidates work. Genera principes In genera, you are ooking for evidence that the candidate knows and understands the point required by the Marking Guideines. It is important to mark what the candidate has written, not to assume what may have been intended. It is aso important to make sure that a vaid point is in the correct context. Individua words or phrases where the overa answer does not appy to the question asked shoud not be credited. Conventions The foowing conventions are used in the Marking Guideines. A semicoon (;) separates each marking point An obique stroke (/) separates aternatives within a marking point Underining of a word or phrase means that the term must be used For exampe anaphase, the term must appear For exampe... and..., both items must be present for a mark Brackets are used to indicate contexts for which a marking point is vaid. This context may be impied by a candidate's answer 'Accept' and 'reject' show answers which shoud be aowed or not aowed. Additiona instructions are shown in the fina coumn Max refers to the maximum mark that can be awarded for a particuar question or part question. The Marking Guideines show the minimum acceptabe answer(s) for each marking point. A better, more detaied, or more advanced answer shoud aways be accepted, provided that it covers the same key point. Marking Guideines cannot give every possibe aternative wording - equivaent phrasing of answers shoud be accepted. For exampe the water potentia is higher in the ces is equivaent to the water potentia is ess negative in the ces. It is, however, important to be sure that the minimum requirement of the Marking Guideines is met and that the point is made unambiguousy. Converse answers are normay acceptabe, uness the wording of the question rues this out. For exampe, 'the water potentia is ower in the soution is an acceptabe converse of the water potentia is higher in the ce. Very occasionay, a candidate wi give a bioogicay correct answer that is not covered in the Marking Guideines. If it is equivaent in standard to the Marking Guideine answers, it shoud be credited. In this case, write the word vaid. A marking points are awarded independenty, uness a ink between points is specified in the Marking Guideines.

4 4 The mechanics of marking Aways mark in red ink. Make sure that some red ink appears on every page on which the candidate has written. For each mark awarded, put a tick cose to the marking point. In a cases, a tick shoud equa one mark and the tota number of ticks shoud match the mark totas in the margins. The tota mark for each part answer shoud be written in the right hand margin. Put a cross against incorrect points. It is hepfu to indicate omissions of key words or incompete answers with a Λ symbo, and to highight irreevancies or contradictions by underining. It is aso hepfu to write brief comments to expain the reason for awarding or withhoding a mark when the answer does not obviousy match the Marking Guideines. When marking answers with many marking points, the points wi be numbered. The points do not have to appear in the candidate s response in the order in the Marking Guideines. The appropriate number must be paced aongside the tick. This heps to carify where a specific point has been awarded and makes moderation much easier. It aso heps to avoid awarding the same point twice. Disquaifiers A correct point shoud be disquaified when the candidate contradicts it in the same answer. Indicate this on the script by 'dq'. If a tick has aready been paced against a vaid point, ensure that it is ceary deeted. Note that there is no penaty for incorrect points which are not contradictory, or for surpus or neutra information. The ist rue When a question asks for a specific number of points, and the candidate gives more, the genera rue is that any wrong answer cances a correct answer. For exampe, if a question asks for two points and three answers are given, two correct and one ceary wrong, the mark awarded is one, whatever the order of the answers. This prevents candidates from gaining fu marks from a ist of right and wrong answers. Name two substances that are produced in photosynthesis. (2 marks) Answer Marks Comment Oxygen, gucose 2 Both correct Oxygen, carbon dioxide 1 One correct, one incorrect Carbon dioxide, oxygen, gucose 1 Carbon dioxide is ceary incorrect and cances one of the marks Oxygen, gucose, water 2 Regard water as a neutra point. It is not worth a mark but it is not incorrect Two or more correct points on the same answer ine shoud be credited. 'Neutra' points, i.e. ones which are not creditworthy but not actuay incorrect, shoud be ignored. Speing Reasonaby cose phonetic speings shoud be credited. However, any misspeing of technica terms which can easiy be confused, such as intermediates between mitosis and meiosis, shoud resut in the reevant marking point being withhed. Terms ike this wi be indicated in the fina coumn in the Marking Guideines to show that misspeings must not be credited. Bioogy - AQA GCE Unit 6T/Q/ Marking Guideines/2011 June series

5 5 Stage 2 (NB No marks are awarded for Stage 1 at A2) Question Marking Guidance Mark Comments 1 Cear statement of nu hypothesis; 1 e.g. the voume of the conica fask has no effect on the size of the yeast popuation / the amount of oxygen has no effect on the density of yeast coonies 2 (a) Standard error (and 95 % confidence imits) / χ 2 ; 1 2 (b) 1 If SE and 95% confidence imits chosen: 2 Compared two means; 3 If 2 χ chosen: 1 4 Number of yeast coonies is categoric; 3 Test statistic cacuated correcty Accept candidate s correct cacuation even if 1 the test is not appropriate. If working not shown, cacuation must be checked against raw data. 4 1 Correct interpretation of statistica test in terms of acceptance or 2 Use candidate s vaue of chosen test even if rejection of nu hypothesis; it is incorrect: 2 Interpretation invoves appropriate reference to the probabiity of the resuts being due to chance; Tota 6 The tabe of raw data and the Stage 2 sheet is required for moderation and must be attached to the ISA test.

6 6 Section A 8 Mix yeast and water / distribute yeast eveny / stop yeast 1 Accept ces as aternative for yeast setting; 5 Aow yeast to reproduce / aow yeast to mutipy / aow (time to 1 Accept ces as aternative for yeast show) effect of oxygen; Reject equiibrate 6 (b) Aows oxygen through / is permeabe to gases / carbon dioxide; Reduces concentration of yeast / diutes yeast; 2 Accept ces as aternative for yeast Accept reference to a questions to bacteria 2 So coonies woud be spread out enough to count / coonies as equivaent to yeast. woud grow from individua ces / coonies woud be separate / coonies easier to count; Question Marking Guidance Mark Comments 6 (a) 1 Prevent contamination by bacteria; 2 max Accept microorganisms / microbes as aternatives for bacteria 2 Bacteria woud compete with the yeast for oxygen / nutrients; 3 Toxins / substances produced by bacteria might inhibit yeast growth; 9 1 Method used to generate a random square; 2 E.g. take numbers from a box / use random button on cacuator / use computer 2 Method used to ocate the square; Do not credit random number generator E.g. number each square 10 1 Larger surface area (in 250 cm 3 fask); 2 2 For diffusion (of oxygen into the cuture);

7 7 Question Marking Guidance Mark Comments 11 1 (More oxygen) aows more respiration / aows aerobic 3 respiration / stops anaerobic respiration / reduces anaerobic respiration; 2 Produces more ATP / reeases more energy; Ignore references to making or producing 3 Energy / ATP used for growth / producing new substances / energy active transport of nutrients / ce division; OR 4 Less anaerobic respiration; 5 Less ethano produced; 6 Ethano kis/inhibits/sows; 12 1 Up to 500 cm 3, voume of fask / oxygen is imiting; 3 Do not penaise candidates if voumes sighty different from vaues quoted. 2 As size of fask increases, number of coonies increases / size of A that is necessary is to identify the reevant fask and number of coonies show positive correation / size of part of the curve. fask and number of coonies are directy proportiona; 3 Above 500 cm 3, voume of fask / oxygen not imiting / something Named factors might be, for exampe, carbon ese imiting / named factor imiting; dioxide, ack of nutrients Tota marks for Section A 17

8 8 Section B Question Marking Guidance Mark Comments 13 1 Shows mass of wheat seedings when grown on their own; 2 2 Aows percentage to be cacuated / aows comparison / aows effect of competition to be seen; Interspecific competition / ryegrass reduces growth of wheat; 4 When marking pease number marking points E.g. 4 means a mark awarded for point Justification by using vaues; % with wheat but ess when grown with ryegrass 3. Competition between shoots had a greater effect than competition between roots; 4. Justification by use of vaues; 4. 46% when shoots compete / in Y / 76% when roots compete / X 15 1 Growth invoves enzymes / enzyme-controed reactions 2 max Accept other vaid physioogica processes such as growth invoves diffusion / ower temperature means ess kinetic energy 2 Lower temperature means ess kinetic energy / fewer coisions / moecues move sower. fewer E S compexes formed; 3 Wheat and ryegrass affected to a different extent; 16 Same number of ryegrass seedings in distied water; 1 17 (a) 1 Produce nu hypothesis; Accept vaid exampe E.g. There is no correation between 2 Carry out Spearman Rank correation test / find correatio 2 max inhibition of germination and the coefficient; concentration of the extract. 3 Use vaues to show P < critica vaue / find probabiity of resuts being due to chance; 17 (b) May be another factor / named factor (that aso inhibits 1 e.g. amount of water in extract germination);

9 9 Question Part Marking Guidance Mark Comments 18 (a) 1 Extract inhibits ryegrass germination / extract stops ryegrass starting to 2 grow; 2 Inhibition of root ength / causes ryegrass to have shorter roots; 18 (b) 1 Scientists crushed pants to get extract; 3 max 2 Pants might not secrete substances in the extract into the soi; 3 These substances might get broken down in the soi; 4 Wheat and ryegrass might not grow at the same time / wheat pants might not produce substance when ryegrass is growing; 5 Concentration of extract in the soi might be different from that in soution; 19 (a) 1 Use no / ess herbicide / weed kier; 2 2 Specific exampe of how ess herbicide / weed kier woud benefit the E.g. woud produce environment; greater diversity of pants. 19 (b) Reduces genetic diversity / gene poo / number of different aees; 2 Wheat unabe to adapt to new conditions / new disease; Tota marks for Section B 21 Copyright 2011 AQA and its icensors. A rights reserved.