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Paper 2 ms - fbwejifk

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Module

Introduction to Physics (AP1840)

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Academic year: 2022/2023
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/

A-level

BIOLOGY

7402/

Paper 2

Mark scheme

June 2023

Version: 1 Final

236a7402/2/MS

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

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 © 2023 AQA and its licensors. All rights reserved.

3 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 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 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 Phonetic spelling

The phonetic spelling of correct scientific terminology should be credited unless there is a possible confusion with another technical term.

3 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 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.

Question Marking Guidance Mark Comments

01.

  1. Draw line/origin on (chromatography) paper (using ruler and pencil);
  2. (Use pipette/tubing/dropper to) add chlorophyll/solution to origin/line;
  3. Add solvent/A below line/origin;
  4. Remove/stop (from glassware) before solvent reaches end (of chromatography paper) OR Mark (position) where solvent reaches/front;

4

(4 x AO1)

Accept all marks on a labelled diagram. Allow filter paper for chromatography paper. 3. Accept ‘so solvent is not above line’ for ‘solvent below line’. 4. Accept remove/stop (immediately) when solvent reaches end/top. 4. Accept ensure solvent does not reach top/end. 4. Ignore Rf values.

Question Marking Guidance Mark Comments

01.

For 2 marks = two pigments have same solubility in (solvent) A but different solubility in (solvent) B OR For 2 marks = one pigment is soluble in (solvent) B but not in (solvent) A OR For 2 marks = pigments have different solubilities in the solvents/A and B

OR For 2 marks = one pigment is only soluble in (solvent) B OR For 2 marks = one pigment is insoluble (only) in (solvent) A;;

For 1 mark = response as for 2 marks but refers to solution rather than solvent;

2

(2 x AO3)

Accept ‘dissolves’ for solubility. Accept correct reference to ‘affinity’ for solubility e., ‘greater affinity’ (to solvent) indicates more soluble. Accept correct reference to ‘polarity’ for solubility’ e. pigments have different polarities. Accept ‘Rf value’ for solubility. Ignore ‘solvent stronger’.

Question Marking Guidance Mark Comments

02.

  1. Rapidly/quickly/directly reaches spinal cord;
  2. Is broken down by enzymes

OR

Is broken down by acid

OR

Is too large to be absorbed; 2 (2 x AO2)

  1. Accept ‘synapses’ for spinal cord.

  2. Accept spinal cord and brain but reject brain on its own.

  3. Accept denatured by acid.

  4. Accept ‘not affected by acid/enzymes’

  5. Reject broken down by named enzymes which are not proteases.

  6. Ignore location of enzymes.

  7. Accept description for ‘absorption’ e. ‘cross the ileum’.

Question Marking Guidance Mark Comments

02.

Correct answer of 5/4(232) x 10

  • = 2 marks;; Answer of 5 or 47(232) with incorrect order of magnitude = 1 mark OR Answer of 2/1(68) x 10 -6 (i., not multiplied by 24) = 1 mark OR Answer of 6/5.8/5 x 10-7 (i., not multiplied by
  1. = 1 mark OR Answer of 2/1.6/1(44) x 10 -5 (i., not multiplied by 3) = 1 mark OR Answer of 6/5.9/5 x 10 -6 (i., not multiplied by
  2. = 1 mark;

2

(2 x AO2)

Accept any equivalent numerical representation of the correct answer. Ignore numbers after 4 and 47.

Question Marking Guidance Mark Comments

02.

  1. (Sensation of) pain is subjective OR Pain sensitivity/threshold/tolerance varies;
  2. To ensure that differences (in pain detection) were (statistically) significant OR For (valid) comparison;

2

(2 x AO3)

  1. Accept ‘could exaggerate pain’.

  2. Accept 'not due to chance' for significant.

  3. Do not credit ‘to determine if results are significant.’

Question Marking Guidance Mark Comments

03.

Correct answer of 12 = 2 marks

OR

Correct answer of 11 = 2 marks;; Incorrect answer but shows 1195 (ignoring orders of magnitude) = 1 mark OR Incorrect answer but shows 1 (Tg) or 13 (Tg) = 1 mark;

2

(2 x AO2)

Accept any numerical representation of the correct answer for two marks. Do not allow 1 or 13 to the incorrect order of magnitude e. x 10 1.

Question Marking Guidance Mark Comments

03.

  1. Kill/remove/no (other) mycorrhizae/fungi;

  2. Kill/remove/no nitrogen-fixing /nitrifying/denitrifying/saprobiotic bacteria;

  3. Kill/remove/no pathogens;

  4. Kill/remove/no pests;

  5. Kill/remove/no competitors;

  6. Kill/remove/no seeds/spores;

  7. Is a (controlled) variable;

2 max (2 x AO2)

1 to 6. Accept in context of organisms being present if soil not sterilised. 2. Accept saprophytes and saprobionts. 3. Accept removes disease-causing bacteria/viruses /microorganisms. 3. Removes ‘harmful bacteria’ is not enough. 4. Accept named pests. 6. Accept weeds or (other) plants.

Question Marking Guidance Mark Comments

03.

  1. So mycorrhizae/water is the only variable OR (So fertiliser) is not a variable OR So fertiliser is a controlled variable;
  2. Affects (crop) production/growth/mass;
  3. (Concentration of fertiliser) would affect water potential of soil;
  4. Does not affect pH (of soil);
  5. To provide (usual) soil/farming conditions;

2 max (2 x AO2)

Ignore leaching and eutrophication.

  1. ‘For comparison’ on its own is not enough.
  2. Accept same amount of fertiliser.
  3. Accept benefits or limiting factor of named nutrient/ion.

Question Marking Guidance Mark Comments

04.

Epistasis OR Epistatic; 1 (AO2)

Ignore any words before or after epistasis e. dominant’. Accept phonetic spellings.

Question Marking Guidance Mark Comments

04 Tortoiseshell female;

1

(AO2)

Accept ‘female tortoiseshell’. Accept ‘ginger & black female’.

Question Marking Guidance Mark Comments

04.

  1. (Gametes) X

G F, X

G f, X

B f and Yf;

2. X

G X

B Ff, X

G X

B ff, X

G YFf and X

G Yff;

  1. White female, Tortoiseshell female, White male, Ginger male, and ratio 1 : 1 : 1 : 1; 3 (3 x AO2)

Allow one mark for correct dihybrid genotypes of offspring from incorrect parental gametes. 1 and 2. Accept if g and b are used throughout for G and B. 2. Accept the alleles within a genotype in any order. 1 and 2. Accept in Punnet square. 2 and 3. Accept any order of genotypes and phenotypes and accept if on incorrect answer lines. 3. Accept sequence of phenotypes does not need to mirror genotypes but must be correct. 3. Accept equivalent ratios e. 4:4:4:4. 3. Accept ‘Ginger and

  1. Do not credit ‘signals’, ‘messages’ for third or fourth options for mark point

Question Marking Guidance Mark Comments

05 Box 3 correct - Several photoreceptors connecting to one neurone and spatial summation

1

(AO1)

Question Marking Guidance Mark Comments

05.

  1. Geographical isolation/separation due to elevation/altitude;
  2. Allopatric speciation due to isolation/separation;
  3. Different selection pressures

OR

Different environment(s);

  1. (However) some overlap in distribution

OR

(Both) plants found in same area/habitat/altitude; 5. So (possibly) sympatric speciation;

  1. (Variation due to) mutation(s);
  2. Reproductive isolation/separation due to different pollinators/distributions/altitudes OR Separate gene pools due to different pollinators/distributions/altitudes;
  3. Change in allele frequency (in each population) OR Different allele frequency (in each population);
  4. Different species) can no longer (interbreed to) produce fertile offspring;

5 max (5 x AO3)

  1. Accept selection (due to) flower colour.
  2. Accept different ‘abiotic conditions/factors’ for ‘different environment(s)’ or different named factor e. temperature, humidity but ‘different altitudes’ on its own is not enough.
  3. Only awarded if mark point 4 is credited.
  4. Reject mutation(s) if context incorrect e. ‘mutate to adapt’.
  5. Accept ‘no gene flow’ for separate gene pools.
  6. Accept ‘increase’ or ‘decrease’ for ‘change’.

Question Marking Guidance Mark Comments

06.

  1. Microvilli provide a large surface area

OR

Folded (cell-surface) membrane provides a large surface area; 2. Many channel/carrier proteins for facilitated diffusion; 3. Many carrier proteins for active transport; 4. Many channel/carrier proteins for co-transport;

  1. Many mitochondria produce ATP OR Many mitochondria for active transport;
  2. Many ribosomes to produce carrier/channel proteins;

3 max (3 x AO1)

Max 2 from mark points 2, 3 and 4. For 2, 3, 4, 5 and 6 penalise omission of ‘many’ only once.

  1. Ignore ’brush border’. 3 and 4. Accept sodium-potassium pumps as an alternative to carrier proteins.
  2. Accept ‘co- transport protein’ or ‘symport’ for type of transport protein.
  3. Accept co-transport for active transport.
  4. Accept abundant rough endoplasmic reticulum for many ribosomes, but abbreviation is not enough.

Question Marking Guidance Mark Comments

06 Collecting duct and distal (convoluted) tubule;

1

(AO1)

Do not accept DCT for distal convoluted tubule.

Question Marking Guidance Mark Comments

06.

  1. Has a (specific) tertiary structure/shape;

  2. (Structures are) complementary; 2 (2 x AO2)

  3. Accept in context of ADH or receptor.

  4. Ignore 3D.

  5. Reject reference to Antigen or antibody.

1 and 2. Reject reference to active site, enzyme, substrate or induced fit only once.

Question Marking Guidance Mark Comments

07.

  1. Heat (loss) from respiration;
  2. (Food) not digested OR Not all eaten;
  3. Excretion;

3

(3 x AO1)

  1. Accept faeces for not digested.

  2. Accept urine/urea for excretion.

Question Marking Guidance Mark Comments

08.

  1. Mutation (in KRAS gene)

OR

Change in base sequence (of KRAS gene); 2. Change in (signalling) protein

OR

More (signalling) protein/K-Ras produced; 3. (Results in) rapid/uncontrollable cell division;

3

(3 x AO2)

  1. Accept named mutation e. substitution.
  2. Accept mutation in promoter gene.
  3. Ignore epigenetic modifications.
  4. Accept change in amino acid sequence (of protein).
  5. Reject ‘no protein produced’ or suggests a non-functional protein is produced.
  6. Accept cell division cannot be regulated.
  7. Ignore growth.
  8. Reject meiosis for cell division, but accept mitosis.

Question Marking Guidance Mark Comments

08.

  1. A/untreated (type II diabetes) lowest survival (time)

OR

A/untreated (type II diabetes) lowers/reduces survival (time compared with control group); 2. B/metformin increases survival (time) the most OR B/metformin has the highest survival (time);

  1. C/combined drugs increases survival (time);
  2. Groups A and B have a significant difference (in survival time compared with control);
  3. Group C has no significant difference (in survival time compared with control);
  4. (In group C) other drugs have reduced effect of metformin

OR

B/metformin is more effective (treatment/drug) than C/combined drugs;

5 max (5 x AO3)

1 to 6. Accept descriptions of each group e. A = no drugs, B = metformin, C = combined drugs. 4 and 5. Reject ‘results are significant’ or ‘results are not significant’ once, but only where there is no indication that these results are ‘different’, ‘greater’, ‘reduced’ etc. 4 and 5. Accept ‘not due to chance’ for ‘significant’ and converse for ‘not significant’. Ignore reference to sample size, repeats or a single study.

Question Marking Guidance Mark Comments

09.

  1. Restriction endonucleases/enzymes;
  2. (Cut DNA) at specific base sequences/pairs

OR

(Cut DNA) at recognition/restriction sites;

2

(2 x AO2)

  1. Accept ‘at palindromic sequences’

Question Marking Guidance Mark Comments

10.

  1. To break actinomyosin (bridges);
  2. To move/bend the myosin head/arm;
  3. (So) actin (filaments) are moved (inwards);
  4. For active transport of calcium ions (into the sarcoplasmic/endoplasmic reticulum);

2 max (2 x AO1)

  1. Accept ‘to form actinomyosin’.

  2. Accept ‘to detach or attach myosin and actin’.

  3. Reject reference to ‘active site’.

  4. Accept ‘to change shape of myosin head/arm’.

  5. Accept ADP/Pi moves (myosin) head/arm.

  6. Accept powerstroke/pivot /recocks etc. for movement.

  7. Ignore ‘sliding’.

Question Marking Guidance Mark Comments

10.

1.

OR

1;

1

(AO2)

Accept numbers after 1.

Question Marking Guidance Mark Comments

10.

  1. Fast (skeletal muscle) fibres used during short-term/intense exercise;
  2. Slow (skeletal muscle) fibres used during long(er)-term exercise;
  3. Creatine used to form phosphocreatine;
  4. (Phosphocreatine) combines with ADP to form ATP;
  5. (Carbohydrate/glucose) stored as glycogen OR Glycogenesis;
  6. Glycogen hydrolysed to glucose

OR

Glycogenolysis; 7. Glucose for respiration;

5 max (5 x AO2)

Max 3 marks from mark points 3, 4, 5, 6 and 7. 1 and 2. Accept examples of short- term/intensity exercise e. sprint and longer- term/endurance exercise, e. marathon or low(er) intensity exercise.

  1. Accept fast twitch fibres for fast (skeletal muscle) fibres
  2. Accept slow twitch fibres for slow (skeletal muscle) fibres.
  3. Accept glycolysis for respiration.
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Paper 2 ms - fbwejifk

Module: Introduction to Physics (AP1840)

47 Documents
Students shared 47 documents in this course

University: University of Central Lancashire

Was this document helpful?
/
A-level
BIOLOGY
7402/2
Paper 2
Mark scheme
June 2023
Version: 1.0 Final
*
236a7402/2/MS
*

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