A-level BIOLOGY 7402/2 Paper 2 Mark scheme June 2022 Version: 1.0 Final

A-level BIOLOGY 7402/2 Paper 2 Mark scheme June 2022 Version: 1.0 Final *226A7402/2/MS* MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 2 Mark schemes are prepared by the Lead Assessment Writer and consider ...

A-level BIOLOGY 7402/2 Paper 2 Mark scheme June 2022 Version: 1.0 Final *226A7402/2/MS* MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 2 Mark schemes are prepared by the Lead Assessment Writer and considered, together with the relevant questions, by a panel of subject teachers. This mark scheme includes any amendments made at the standardisation events which all associates participate in and is the scheme which was used by them in this examination. The standardisation process ensures that the mark scheme covers the students’ responses to questions and that every associate understands and applies it in the same correct way. As preparation for standardisation each associate analyses a number of students’ scripts. Alternative answers not already covered by the mark scheme are discussed and legislated for. If, after the standardisation process, associates encounter unusual answers which have not been raised they are required to refer these to the Lead Examiner. It must be stressed that a mark scheme is a working document, in many cases further developed and expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark schemes on the basis of one year’s document should be avoided; whilst the guiding principles of assessment remain constant, details will change, depending on the content of a particular examination paper. Further copies of this mark scheme are available from aqa.org.uk Copyright information AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third party even for internal use within the centre. Copyright © 2022 AQA and its licensors. All rights reserved. MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 3 Mark scheme instructions to examiners 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. MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 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. MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 5 Question Marking Guidance Mark Comments 01.1 1. Organic 2. Respiration 3. Carbon 4. Calorimetry;; 2 (2 x AO1) 4 correct = 2 marks 2–3 correct = 1 mark 0–1correct = 0 marks 2. Ignore aerobic/anaerobic. 3. Accept cells/tissue(s)/plant(s)/animal(s)/organism(s)/ NPP/ living material/biological molecules. 3. Ignore biomass/biological materials/organic matter and reference to ‘dry’. 4. Accept calorimeter but reject colorimeter. 4. Accept phonetic spellings. Question Marking Guidance Mark Comments 01.2 1. Carbon dioxide combines/reacts with ribulose bisphosphate/RuBP; 2. Produces two glycerate (3- )phosphate/GP using (enzyme) Rubisco; 3. GP reduced to triose phosphate; 4. Using reduced NADP; 5. Using energy from ATP; 6. Triose phosphate converted to glucose/hexose/RuBP/ribulose bisphosphate/named organic substance; 6 (6 x AO1) 1 to 6. Accept marks in suitable diagram. 1. Accept idea of fixation for ‘reacts’. 2. Accept: any answer which indicates that 2 × as much GP produced from one RuBP catalysed by Rubisco. 2 and 3. Reject GP once if incorrectly named e.g., glucose 3- phosphate. 3. Must have idea of reduction. This may be conveyed by stating mp4. 3 and 6. Only accept TP if triose phosphate is also in the answer. However only penalise once. 4. Accept NADPH or NADPH2 or NADPH + H for reduced NADP. 4. Reject: Any reference to reduced NAD for mp4 but allow reference to reduction for mp3. 4. and 5. must be in context of GP to triose phosphate. MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 6 Question Marking Guidance Mark Comments 02.1 Automarked question –  N = I – (F + R); (Box 2) 1 (AO1) Question Marking Guidance Mark Comments 02.2 21.6 OR 22; 1 (AO2) Question Marking Guidance Mark Comments 02.3 Correct answer of 88500/89000 = 2 marks;; Incorrect but shows 1.8975/1.898/1.9/1.90 (million) /1897500 = 1 mark OR Incorrect but shows 1.809/1.81/1.8/1.80 (million) / 1809000 = 1 mark OR Incorrect but shows 885/89/90 with incorrect position of decimal point = 1 mark; 2 (2 x AO2) Accept 90000 for 2 marks. Accept any of the answers in any correct mathematical form e.g., shows 1.8 (million) as 1800000. Question Marking Guidance Mark Comments 02.4 1. Energy lost between/at trophic/feeding levels; 2. Energy lost via respiration/excretion/faeces; 2 (2 x AO2) 1. Accept description of trophic levels e.g., food chain. 2. Accept energy lost via heat/metabolism/food not eaten/digested /muscle contraction/movement /maintaining temperature. 2. Reject energy used in respiration. 2. Reject energy produced/generated. MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 7 Question Marking Guidance Mark Comments 03.1 1. Volume of (stock) bacteria (culture); 2. Concentration of (stock) bacteria (culture); 3. Concentration of glucose OR Concentration of (respiratory) substrate; 4. Volume of ammonium chloride; 5. Time (bacteria/culture left to divide); 6. Concentration/volume of oxygen; 7. Concentration/volume of nitrogen; 2 max (2 x AO2) Accept vol. for volume and conc. for concentration. 1 and 2. If neither credited accept number/mass of bacteria for 1 mark. 1 and 2. Ignore volume/concentration of liquid culture. 3. Accept concentration of ion/named ion but ignore ammonium chloride. Ignore ‘same bacteria/species/type’. 1, 2, 3, 4, 6. and 7. Ignore amount. 3. Ignore ‘sugar’. 3 and 4. Ignore nutrients. 6 and 7. Ignore availability/access/exposure. Question Marking Guidance Mark Comments 03.2 (For) 1. Nitrogenase activity decreases with increase in ammonium chloride (concentration); 2. Nitrogenase activity zero with high (concentration of) ammonium chloride OR Ammonium chloride remains (in medium) when nitrogenase activity zero; (Against) 3. Only used one species; 4. (Inhibition/results) may be due to chloride (ions) 3 max (3 x AO3) 1 and 2. Accept ammonia for ammonium chloride. 1. Accept negative correlation between nitrogenase activity and ammonium chloride (concentration). 2. Accept nitrogenase activity zero at 80/100/120/above 60 (µg cm3 of ammonium chloride). 2. Accept ‘stops’ for zero. 3. Accept only Azotobacter/A. chroococcum / chroococcum / one nitrogenfixing bacterium / one type/strain used. MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 8 OR (Investigation) uses ammonium chloride not ammonia; 4. Reject ‘chlorine’. Ignore reference to statistical tests. Question Marking Guidance Mark Comments 03.3 1. Less/no ATP/energy required/used OR More ATP/energy available; 2. ATP/energy can be used for growth/synthesis/replication OR Lower (rate of) respiration required OR ATP for phosphorylation; 2 (2 x AO2) 2. Accept ATP can be used for ‘other reactions’, ‘movement’, ‘active transport’ or correctly named reaction. 2. Ignore ‘aerobic’, ‘anaerobic’ in context of respiration. 2. Reject ATP/energy used for/in respiration. 2.Reject mitosis. Question Marking Guidance Mark Comments 04.1 Automarked question –  Reduction of pyruvate (Box 3) 1 (AO1) MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 9 Question Marking Guidance Mark Comments 04.2 1. Oxygen/O2 taken up/used (by seeds); 2. Carbon dioxide/CO2 (given out) is absorbed by solution/potassium hydroxide/KOH; 3. Decrease in pressure/volume (of air inside); 3 (3 x AO2) 3. Ignore ‘negative pressure’ but reject reference to vacuum. 3. Accept ‘air pressure higher than inside’. Question Marking Guidance Mark Comments 04.3 1. Distance (drop/liquid moves); 2. Diameter/radius/bore of tubing/lumen; 2 (2 x AO2) Ignore time. 1.Accept description of distance, e.g. ‘start and end position’. 2. Accept (crosssectional) area of tubing/lumen. Question Marking Guidance Mark Comments 04.4 1. Remove potassium hydroxide/KOH OR Remove solution which removes carbon dioxide. OR Replace potassium hydroxide/KOH with water; 2. Record distance liquid moves (without potassium hydroxide); 3. Use difference in distance liquid moves (with potassium hydroxide and without potassium hydroxide) OR Use difference in (calculated) volumes (with potassium hydroxide and without potassium hydroxide); 3 (3 x AO3) Answers which add/use a syringe, reject mp2 and mp3. 1. Reject if seeds removed or another organism used. 2. Reject moves to the right. 2. Accept ‘liquid would not move’. 3. Accept ‘if liquid does not move (volume of) carbon dioxide produced is the same as (volume of) oxygen used’. MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 10 Question Marking Guidance Mark Comments 04.5 Answer in the range 3 × 10–7 to 3.33 × 10–7 ; 1 (AO2) Accept equivalent answers in this range which are not in standard form. Accept 3.0 x 10-7 Ignore any numbers after 3.33. MARK SCHEME – A-LEVEL BIOLOGY – 7402/2 – JUNE 2022 11 Question Marking Guidance Mark Comments 05.1 1. E. rufus in north (west) OR E. rufus in the west OR E. rufus above river; 2. E. rufifrons in south OR E. rufifrons in west and east OR E. rufifrons below river; 3. (Actual) distribution similar to expected (distribution) OR (Actual) distribution similar to environmental needs OR (Actual) distribution (slightly) less than expected distribution; 3 (3 x AO3) 1 and 2. Accept equivalent valid statements e.g., for 1, no E. rufus in south. 1 and 2. If neither mark is awarded, accept, for one mark, ‘they are separated by the river’ OR ‘there is no overlap in their distribution/ranges’. 1 and 2. Accept converse. 1 and 2. Do not penalise ‘prefer’. 3. Accept for one or both species. Question Marking Guidance Mark Comments 05.2 1. Geographical isolation OR Allopatric speciation; 2. Reproductive separation/isolation OR No gene flow OR Gene pools separate; 3. Different selection pressures OR 5 max (3 x AO1, 2 x AO2) 1.Ignore d