Marking Guidelines 2010 examination June series. Biology Unit 3T AS Investigative Skills Assignment. General Certificate of Education BIO3T/Q10/MG

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1 Genera Certificate of Education Bioogy Unit 3T AS Investigative Skis Assignment BIO3T/Q10/MG Marking Guideines 2010 examination June series WMP/Jun10/BIO3T/Q10/MG

2 Marking Guideines are prepared by the Principa Moderator and considered, together with the reevant questions, by a pane of subject teachers. Copyright 2010 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. Dr Michae Cresswe Director Genera 2

3 Guidance for teachers marking Bioogy ISAs 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. 3

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. 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 caces 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 not negate a correct answer. Speing Reasonaby cose phonetic speings shoud be credited. However, any misspeing of technica terms which can easiy be confused, such as intermediate 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. 4

5 Stage 1 Assessment of presentation of raw data tabes Candidates shoud be assessed on their abiity to present raw data in an appropriate way. The foowing criteria shoud be used to mark this ski. Part 1 Making the standards Marking Guidance Mark Comments Tabe 1 competey correct; 1 Check that: voume of beetroot extract pus voume of water totas 5 cm 3 percentage concentration correct for candidate s voume vaues for percentage concentration of extract equay spaced Tota 1 Part 2 The investigation Marking Guidance Mark Comments Data presented ceary with a fu description of both the independent and This may be recorded either by a fu tite or dependent variabe, i.e. acoho concentration and coour vaue. 1 by compete headings on the top of the tabe. Independent variabe (concentration of acoho) in the first coumn; 1 Units ceary stated and ony in the heading to the appropriate coumns: 1 e.g. % (of acoho), arbitrary units or % of extract (coour vaue) Tota 3 The data tabes are required for moderation and must be attached to the ISA written test. 5

6 Stage 2 Assessment of processing Marking Guidance Mark Comments Graph has independent variabe (concentration of acoho) on x axis and dependent variabe (coour vaue or concentration of extract) on y axis; 1 Both axes correcty abeed with appropriate units 1 Accept % acoho i.e. acoho / %, coour vaue / arbitrary units or % of extract Appropriate scaes seected for the x and y axes; 1 These scaes shoud aow for both accurate potting and reading of the graph A points potted accuratey; 1 If ICT has been used to pot the graph, it shoud be possibe to read the points with appropriate precision Data presented as a ine graph; Depending on the data obtained by the student: points shoud be joined with a curve of best fit if it is fet that intermediate vaues are ikey to fa on such a curve aternativey, a points shoud be joined with straight ines if it is fet that the position of intermediate points cannot be predicted reiaby. no marks shoud be awarded if the curve is extrapoated beyond the range of data coected. Tota 5 The graph produced is required for moderation and must be attached to the ISA written test. 6

7 SECTION A Question Marking Guidance Mark Comments 1 To wash off any pigment / betains (on the discs); To show that any pigment reeased is from the effect of acoho; 1 max 2 (a) (Distied) water and (two) discs of beetroot; 1 2 (b) To show that the acoho was causing the eakage of pigment / to compare it with the effects of the acoho; 1 3 (a) Increase the contact of a surfaces with the acoho / prevent discs sticking together / maintain a diffusion gradient for the pigment; 1 3 (b) To imit the variation in time discs are in acoho / make sure Accept fair test if a the discs were in contact with acoho for the same ength of time / quaified by reevant so no more pigment can diffuse out of the discs; 1 marking point 4 Heating / cooking woud damage the (pasma) membranes; Do not accept reference Vaid expanation of damage e.g. disrupts phosphoipid to kiing membrane biayer / denatures proteins; A ot of pigment reeased during cooking / ess pigment present (in tissue); 2 max 5 Less kinetic energy; Moecues move sower; Lower rate of diffusion; Membranes ess fuid; 2 max 7

8 SECTION A continued Question Marking Guidance Mark Comments 6 Variation in beetroot / variation in judging coour; 1 Credit any vaid variation 7 (a) No (no mark) Curve drawn on graph shoud not extend beyond data coected / no contro carried out with water; 1 7 Phosphoipids are in the membranes; Membrane breaks down faster / more at higher concentration of acoho / (higher concentration of acoho) increases the permeabiity of membranes; (Aows) faster rate of diffusion of pigment; More betains / pigments move out of ces / vacuoes; 3 max (b) 8 (a) Repeat experiment at 100 % acoho concentration; Check to see if resuts are concordant / simiar; 2 8 (b) Concentration of pigment inside and outside of the tissue reached Do not accept a equiibrium / an equa concentration of pigment inside and outside the pigment has beetroot / pigment diffusing in and out at the same rate; diffused out Maximum membrane damage; 1 max Tota marks for Section A 17 8

9 Section B Question Marking Guidance Mark Comments 9 Fatty acids used to make phosphoipids; Phosphoipids in membranes; More phosphoipids more membranes made; 2 max Fatty acids respired to reease energy; Do not aow credit for More trigycerides more energy reeased; making energy Energy used for ce production / production of named ce component; 2 max 10 (Omega-3 concentration) fas more rapidy at first; Leves out at 140 days / concentration of 0.4 %; 2 9

10 \ Section B continued Question Marking Guidance Mark Comments 11 (a) Two marks for correct answer of 0.04 or 0.043;; One mark for incorrect answer which ceary identifies tota fa of 1.7; 2 11 (b) To take into account variation in fat content of mik / fat content varies from cow to cow; 2 Aows comparison; 11 (c) The graph shows a decrease with time feeding on corn; No contro group; Might have faen anyway / might decrease with time rather than with time spend feeding on corn; Other factors / other named factor might aso have changed; Ony one investigation so might not be representative; 4 max 12 Standard deviation shows there is overap of the 2 data sets; Sma sampe of wid samon so may not be representative of popuation; 2 13 The different diet of the fish; Omega-3 fatty acids used in respiration / as a source of energy; Wid trout are more active / use more energy; 2 max Tota marks for Section B Copyright 2010 AQA and its icensors. A rights reserved.