Specimen QP Paper AQA Biology A Level_aqa_as_level_biology_paper_2_2020_mark_scheme.

Specimen QP Paper AQA Biology A Level_aqa_as_level_biology_paper_2_2020_mark_scheme. 1. General The mark scheme for each question shows: • the marks available for each part of the question • the total marks available for the question • the typical answer or answers which are expected • Extra information to help the examiner make his or her judgement and help to delineate what is acceptable or not worthy of credit or, in discursive answers, to give an overview of the area in which a mark or marks may be awarded. The extra information in the ‘Comments’ column is aligned to the appropriate answer in the lefthand part of the mark scheme and should only be applied to that item in the mark scheme. At the beginning of a part of a question a reminder may be given, for example: where consequential marking needs to be considered in a calculation; or the answer may be on the diagram or at a different place on the script. In general the right-hand side of the mark scheme is there to provide those extra details which confuse the main part of the mark scheme yet may be helpful in ensuring that marking is straightforward and consistent. 2. Emboldening 2.1 In a list of acceptable answers where more than one mark is available ‘any two from’ is used, with the number of marks emboldened. Each of the following bullet points is a potential mark. 2.2 A bold and is used to indicate that both parts of the answer are required to award the mark. 2.3 Alternative answers acceptable for the same mark are indicated by the use of OR. Different terms in the mark scheme are shown by a/; eg allow smooth/free movement. 3. Marking points 3.1 Marking of lists This applies to questions requiring a set number of responses, but for which students have provided extra responses. The general principle to be followed in such a situation is that ‘right + wrong = wrong’. Each error/contradiction negates each correct response. So, if the number of errors/contradictions equals or exceeds the number of marks available for the question, no marks can be awarded. However, responses considered to be neutral (often prefaced by ‘Ignore’ in the ‘Comments’ column of the mark scheme) are not penalised. S - The Marketplace for Revision Notes & Study Guides Downloaded by: kavijanananth | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2020 4 3.2 Marking procedure for calculations Full marks can be given for a correct numerical answer, without any working shown. However, if the answer is incorrect, mark(s) can usually be gained by correct substitution/working and this is shown in the ‘Comments’ column or by each stage of a longer calculation. 3.3 Interpretation of ‘it’ Answers using the word ‘it’ should be given credit only if it is clear that the ‘it’ refers to the correct subject. 3.4 Errors carried forward, consequential marking and arithmetic errors Allowances for errors carried forward are most likely to be restricted to calculation questions and should be shown by the abbreviation ECF or consequential in the mark scheme. An arithmetic error should be penalised for one mark only unless otherwise amplified in the mark scheme. Arithmetic errors may arise from a slip in a calculation or from an incorrect transfer of a numerical value from data given in a question. 3.5 Phonetic spelling The phonetic spelling of correct scientific terminology should be credited unless there is a possible confusion with another technical term. 3.6 Brackets (…..) are used to indicate information which is not essential for the mark to be awarded but is included to help the examiner identify the sense of the answer required. 3.7 Ignore/Insufficient/Do not allow Ignore or insufficient is used when the information given is irrelevant to the question or not enough to gain the marking point. Any further correct amplification could gain the marking point. Do not allow means that this is a wrong answer which, even if the correct answer is given, will still mean that the mark is not awarded. S - The Marketplace for Revision Notes & Study Guides Downloaded by: kavijanananth | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2020 5 Question Marking Guidance Mark Comments 01.1 1. Select at random; 2. Large sample/number (of snails)/10; 2 1. Accept description of random technique 2. Ignore ‘many’ 01.2 Mean and standard deviation; 1 Accept 2 correct statistical values for 1 mark Accept any order Accept average for mean Accept standard error for standard deviation Accept interquartile range 01.3 (Littorina -) genus and (littorea -) species; 1 Accept phonetic spelling Accept genera 01.4 1. No (significant) difference between (mean) height (in these populations); 2. (Students) t-test; 2 Accept suitable null hypothesis TOTAL 6 S - The Marketplace for Revision Notes & Study Guides Downloaded by: kavijanananth | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2020 6 Question Marking Guidance Mark Comments 02.1 1. Condensation (reaction)/loss of water; 2. (Between) phosphate and deoxyribose; 3. (Catalysed by) DNA polymerase; 2 max 3. Reject if DNA polymerase joins AT/GC OR complementary nucleotides/bases OR forms hydrogen bonds 02.2 Correct answer for 2 marks = 70;; Accept for 1 mark, A = 42 and T = 42 OR 420 (total bases in gene) OR 210 (bases in template strand) 2 02.3 Histone; 1 02.4 1. DNA helicase; 2. Breaks hydrogen bonds between base pairs/ AT and GC/complementary bases OR Breaks hydrogen bonds between polynucleotide strands; 2 2. Reject hydrolysis of hydrogen bonds TOTAL 7 S - The Marketplace for Revision Notes & Study Guides Downloaded by: kavijanananth | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2020 7 Question Marking Guidance Mark Comments 03.1 1. Muscle contracts; 2. Constricts/narrows arteriole/lumen; 2 2. Accept decreases for constricts/narrows 2. Accept vasoconstriction for 1 mark 03.2 (Ventricles and arteries) 1. Ventricle (muscles) relaxed OR Arteries recoiled; 2. No (blood) backflow (into ventricles) OR No blood movement to/in/from arteries; (Atria and ventricles) 3. Atria (muscle) contracted; 4. Blood movement from atria (into ventricles); 4 Accept references to ventricle, artery or atrium (singular) 1. Accept no muscle activity OR Diastole OR Arteries smoothing blood flow 2. and 4. Accept flow/pumped for movement 03.3 Vena cava; 1 03.4 2 marks for correct answer = 130 (beats min−1 );; 1 mark for correct stroke volume = 104 2 TOTAL 9 S - The Marketplace for Revision Notes & Study Guides Downloaded by: kavijanananth | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2020 8 Question Marking Guidance Mark Comments 04.1 Measure temperature (in tube) at intervals and use appropriate corrective measure (if temperature has fluctuated); 1 Accept use thermometer/probe/ equivalent device for measure temperature 04.2 1. Length and diameter OR Surface area OR Volume OR Mass/weight (of cylinders); 2. Time in solution; 2 1. Ignore shape/size 2. Ignore ‘time’ if unqualified 04.3 1. 1; 2. Use instrument with closer/finer/smaller intervals/graduations/scale; 2 2. Accept correct numerical figure, eg 2 (cm3 ) 2. Ignore ‘higher resolution’ 04.4 1. Water/25oC caused no damage/no pigment release (in E); 2. (Damage to) cell(-surface) membrane; 3. Ethanol/acid caused some/similar/identical damage OR 70oC caused most damage; 4. (By) ethanol dissolving phospholipid bilayer OR (By acid) altering membrane protein; 5. (By) 70oC denaturing/altering membrane protein OR (By) 70oC increasing fluidity/permeability of membrane; 4 max 1. Accept no colour/intensity change for ‘pigment’ Accept ‘high temperature’ for 70oC 1. and 3. Accept description of ‘pigment release’ for ‘damage’ 2. Accept description of membrane, eg phospholipid bilayer/bilayer 4. and 5. Accept carrier OR channel OR intrinsic OR extrinsic protein for membrane protein 5. Ignore reference to enzymes unless qualified as membrane bound S - The Marketplace for Revision Notes & Study Guides Downloaded by: kavijanananth | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides MARK SCHEME – AS BIOLOGY – 7401/2 – JUNE 2020 9 TOTAL 9 Question Marking Guidance Mark Comments 05.1 1. Starch (solution) in first column; 2. Headings for starch concentration/solution and time for (starch) hydrolysis/digestion with mg dm-3 and minutes/mins/min/m/seconds/s; 2 Ignore columns with replicates/ mean Ignore lines 2. Accept brackets for solidus 2. Ignore reference to enzyme 2. Reject graph 05.2 1. As starch concentration increases, time to hydrolyse/digest starch increases; 1 Accept converse 05.3 1. Inhibitor similar shape to substrate; 2. Fits/binds to active site; 3. Prevents/reduces enzyme-substrate complex forming; 3 1. Reject same shape 1. Accept ‘complementary to active site’ 05.4 1. Less hydrolysis of starch; 2. (To) maltose; 3. (So) less absorption (of glucose) OR (So) more egested (starch/carbohydrate); 3 1. Accept no hydrolysis 3. Accept description of egestion, eg lost in faeces TOTAL 9