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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2008 question paper 9700 BIOLOGY 9700/31 Paper 31 (Advanced Practical 1), maximum raw mark 40 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the report on the examination. CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2008 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.
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Page 2 Mark Scheme Syllabus Paper GCE A/AS LEVEL October/November 2008 9700 31 © UCLES 2008 Question Expected Answers Additional Guidance Marks Record OBSERVATIONS and NUMERICAL MEAN DEGREE OF PLASMOLYSIS 2PDO recording, 2MMO collection, 2MMO decision. 1 (a) (i) table, AND plasmolysis/numerical (estimate) ; shows 5 cells recorded per solution; (water) 1 or label; ( S1 ) number more than water or label; ( S2 ) number between S1 and water or label; (all table) cells drawn between different text AND ( heading above data) W or water or 0 and S1 or 1 and S2 or 0.5; Ignore units. Look at mean first (if there) so should be 1 – ignore any decimal places. Numbers mostly 1 if 5 cells recorded. Mark best table, ignore any additional text or drawings. No outer boundary needed. Any evidence of five cells only, e.g. five drawn per solution or total cells 5 or 1 + 3 + 2 + 1 + 1 1 2 3 4 none slight extensive severe Allow any correct numbers. Ignore decimal places. [6] Describe and explain observations from water, S1 and S2 . 3 MMO decisions 1 (a) (ii) Idea of 1. high/0 to low/ from higher to lower less negative/0 to more negative water potential/ down water potential gradient 2. (in water) cells turgid/no or slight plasmolysis 3. (in S1 ) cells plasmolysed/flaccid/described OR (in S2 ) no/less/capped plasmolysis/described accept cytoplasm/cell membrane pulled away from cell wall /vacuole shrinks. Reject cell shrinks AND by osmosis; AND water has moved in/no net movement/correct idea of water out; AND water moved out; AND no net movement/water moved out; In correct context. Accept ψ . Solute/osmotic potential is ignored but
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This note was uploaded on 09/30/2011 for the course BIOLOGY 425 taught by Professor Prof.yemanga during the Spring '11 term at Bethany CA.

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