Practice paper - Set 1 A Level Biology A. H420/03 Unified biology MARK SCHEME, Exams of Biology

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Practice paper - Set 1

A Level Biology A.

H420/03 Unified biology

MARK SCHEME

Duration: 1 hour 30 minutes

MAXIMUM MARK 70

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FINAL

This document consists of 12 pages

Mark Scheme Practice paper – Set 1 MARKING INSTRUCTIONS PREPARATION FOR MARKING SCORIS

1. Make sure that you have accessed and completed the relevant training packages for on-screen marking: scoris assessor Online Training ; OCR Essential Guide to Marking.
2. Make sure that you have read and understood the mark scheme and the question paper for this unit. These are posted on the RM Cambridge Assessment Support Portal http://www.rm.com/support/ca
3. Log-in to scoris and mark the required number of practice responses (“scripts”) and the required number of standardisation responses. YOU MUST MARK 10 PRACTICE AND 10 STANDARDISATION RESPONSES BEFORE YOU CAN BE APPROVED TO MARK LIVE SCRIPTS.

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MARKING

1. Mark strictly to the mark scheme.
2. Marks awarded must relate directly to the marking criteria.
3. The schedule of dates is very important. It is essential that you meet the scoris 50% and 100% (traditional 50% Batch 1 and 100% Batch 2) deadlines. If you experience problems, you must contact your Team Leader (Supervisor) without delay.
4. If you are in any doubt about applying the mark scheme, consult your Team Leader by telephone, email or via the scoris messaging system. Mark Scheme Practice paper – Set 1
5. Work crossed out: a. where a candidate crosses out an answer and provides an alternative response, the crossed out response is not marked and gains no marks b. if a candidate crosses out an answer to a whole question and makes no second attempt, and if the inclusion of the answer does not cause a rubric infringement, the assessor should attempt to mark the crossed out answer and award marks appropriately.
6. Always check the pages (and additional objects if present) at the end of the response in case any answers have been continued there. If the candidate has continued an answer there then add a tick to confirm that the work has been seen.
7. There is a NR (No Response) option. Award NR (No Response)
   • if there is nothing written at all in the answer space
   • OR if there is a comment which does not in any way relate to the question (e.g. ‘can’t do’, ‘don’t know’) - OR if there is a mark (e.g. a dash, a question mark) which isn’t an attempt at the question. Note: Award 0 marks – for an attempt that earns no credit (including copying out the question).

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8. The scoris comments box is used by your Team Leader to explain the marking of the practice responses. Please refer to these comments when checking your practice responses. Do not use the comments box for any other reason. If you have any questions or comments for your Team Leader, use the phone, the scoris messaging system, or email.
9. Assistant Examiners will send a brief report on the performance of candidates to their Team Leader (Supervisor) via email by the end of the marking period. The report should contain notes on particular strengths displayed as well as common errors or weaknesses. Constructive criticism of the question paper/mark scheme is also appreciated. 3 Mark Scheme Practice paper – Set 1
10. For answers marked by levels of response: Read through the whole answer from start to finish, concentrating on features that make it a stronger or weaker answer using the indicative scientific content as guidance. The indicative scientific content indicates the expected parameters for candidates’ answers, but be prepared to recognise and credit unexpected approaches where they show relevance. Using a ‘best-fit’ approach based on the science content of the answer, first decide which set of level descriptors, Level 1, Level 2 or Level 3, best describes the overall quality of the answer using the guidelines described in the level descriptors in the mark scheme. Once the level is located, award the higher or lower mark. The higher mark should be awarded where the level descriptor has been evidenced and all aspects of the communication statement (in italics) have been met. The lower mark should be awarded where the level descriptor has been evidenced but aspects of the communication statement (in italics) are missing.

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In summary:

• The science content determines the level.
• The communication statement determines the mark within a level. Level of response questions on this paper are 1(c) and 3(a).

11. Annotations Annotation Meaning DO NOT ALLOW Answers which are not worthy of credit IGNORE Statements which are irrelevant ALLOW Answers that can be accepted ( ) Words which are not essential to gain credit __ Underlined words must be present in answer to score a mark ECF Error carried forward AW Alternative wording ORA Or reverse argument

12. Subject-specific Marking Instructions INTRODUCTION Your first task as an Examiner is to become thoroughly familiar with the material on which the examination depends. This material includes:
    • the specification, especially the assessment objectives • the question paper
    • the mark scheme. You should ensure that you have copies of these materials. You should ensure also that you are familiar with the administrative procedures related to the marking process. These are set out in the OCR booklet Instructions for Examiners. If you are examining for the first time, please read carefully Appendix 5 Introduction to Script Marking: Notes for New Examiners. Please ask for help or guidance whenever you need it. Your first point of contact is your Team Leader. Question Answer Marks Guidance 1 a no sexual reproduction  no / little , genetic variation  idea of susceptible to new diseases  idea of susceptible to changing environment 

ALLOW idea of limited gene pool

b Feature Cause of feature Number of genes involved Type of graph used to present data Circumference (mm) environment and genes / genetics many / several / polygenic / AW line graph Containing seeds or seedless genes / genetics^ one / two^ bar , chart / graph    3 One mark per correct column ALLOW histogram instead of line graph c Please refer to the marking instructions on page 4 of this mark scheme for guidance on how to mark this question. In summary: Read through the whole answer. (Be prepared to recognise and credit unexpected approaches where they show relevance.) Using a ‘best-fit’ approach based on the science content of the answer, first decide which of the level descriptors, Level 1 , Level 2 or Level 3 , best describes the overall quality of the answer. Then, award the higher or lower mark within the level, according to the Communication Statement (shown in italics): o award the higher mark where the Communication Statement has been met. o award the lower mark where aspects of the Communication Statement have been missed.

**_- The science content determines the level.

• The Communication Statement determines the mark within a level._** Level 3 (5-6 marks) Includes detailed explanations for most of the observations, with clear links to the correct hormone treatment and including relevant biochemical details where appropriate. 6 Indicative scientific points may include: shorter roots high auxin concentrations / auxin in addition to the natural production

There is a well-developed line of reasoning, which is clear and logically-structured and uses scientific terminology at an appropriate level. All the information presented is relevant and forms a continuous narrative. inhibits root growth taller gibberellins promote stem elongation Question Answer Marks Guidance Level 2 (3-4 marks) Includes explanations for some of the observations, with some links to the correct hormone treatment and/or including relevant biochemical details. There is a line of reasoning presented with some structure and use of appropriate scientific language. The information presented is mostly relevant. Level 1 (1-2 marks) A limited number of observations included in the response, without clear links to the correct hormone treatment and/or including only limited biochemical detail. There is a logical structure to the answer. The explanation and use of scientific language, though basic, is clear. 0 marks No response or no response worthy of credit. by stimulating cell elongation and division growth timing gibberellins promote seed germination by activating genes for amylase and protease enzymes, which break down food stores. side branches auxin maintains apical dominance and inhibits the growth of lateral shoots/branches. delayed fruit and leaf fall (a small addition of) auxin slows down fruit drop and leaf fall. Auxin inhibits abscission by preventing ethene production from increasing. 2 a NO YES NO NO YES  2 ALL CORRECT = 2 marks 3 CORRECT = 1 mark ALLOW correct placement of ticks and crosses in the boxes, if clear and unambiguous b i A = Glomerulus  B = Bowman’s capsule  2 ALLOW capillary (network) ii 190  2 AWARD ONE MARK for: 0.03 or 3 / 160

c i initial / AW , glucose concentration (on both sides on the membrane)  volume of solution  length / diameter , of dialysis tubing  type / brand , of dialysis tubing 

Question Answer Marks Guidance ii alpha glucose H above ring / OH below ring , on , carbon 1 / C1 ORA  1 ALLOW a suitable annotated diagram iii ( less reabsorption because ) idea of fewer H+^ ions in PCT cells  less / no , co-transport / facilitated diffusion , of Na+^ ions , into cells / from lumen less / no , active transport of Na+^ ions into , blood 

d Conclusion: No because month 3 is above 60 cm^3 min-1^  Month 2: 48.5 cm^3 min- Month 3: 67.2 cm^3 min- Month 4: 58.2 cm^3 min-1^ 

The second mark is for 3 correct calculations 3 a Please refer to the marking instructions on page 4 of this mark scheme for guidance on how to mark this question. In summary: Read through the whole answer. (Be prepared to recognise and credit unexpected approaches where they show relevance.) Using a ‘best-fit’ approach based on the science content of the answer, first decide which of the level descriptors, Level 1 , Level 2 or Level 3 , best describes the overall quality of the answer. Then, award the higher or lower mark within the level, according to the Communication Statement (shown in italics): o award the higher mark where the Communication Statement has been met. o award the lower mark where aspects of the Communication Statement have been missed.

**_- The science content determines the level.

• The Communication Statement determines the mark within a level._** Level 3 (5-6 marks) A comparison of all or most aspects of the two processes is included, with no significant errors. 6 Indicative scientific points may include: Similarities - DNA unwinds and unzips

There is a well-developed line of reasoning, which is clear and logically-structured and uses scientific terminology at an appropriate level. All the information presented is relevant and forms a continuous narrative. Level 2 (3-4 marks) A description of some similarities and differences between the two processes is included, with only minor errors.

• Helicase enzymes
• Template DNA
• Complementary base pairing
• Hydrogen bonds
• Free, activated nucleotides
• Polymerase enzymes Question Answer Marks Guidance There is a line of reasoning presented with some structure and use of appropriate scientific language. The information presented is mostly relevant. Level 1 (1-2 marks) A description of similarities or differences between the two processes is included, but with significant omissions or errors. There is a logical structure to the answer. The explanation and use of scientific language, though basic, is clear. 0 marks No response or no response worthy of credit. Differences
• Only a small section of DNA (where the gene is located) unzips during transcription
• Both strands act as templates in replication
• RNA vs DNA free nucleotides
• RNA vs DNA polymerase
• Different helicase enzymes
• Products are two new daughter strands of DNA in replication and one mRNA strand in transcription
• mRNA leaves nucleus whereas the new DNA strand remains bound to the template strand b i radioactive , labels / tags  fluorescent , labels / tags  UV , light / radiation  (named) visible stain 

ii X placed on any fragment below Y  1 X can be placed in any of the 9 lanes, but must be touching a DNA band that

is lower in the image (nearer the cathode) than Y c i denature / unfold , protein AND idea of exposes charges or hydrophobic region  1 ii idea that different proteins have different overall charges  idea that (binding of) SDS makes all proteins negatively charged  idea that proteins will be separated by , mass / length  idea that proteins move in the same direction 

Question Answer Marks Guidance 4 a i no / less , planting AND idea of trees remove water from the bog  no ditch AND idea of ditch drains water from the bog  no / controlled , grazing AND idea of overgrazing disrupts the food chain  no / less , burning AND idea of death of organisms from rare species 

a ii idea that preservation leaves ecosystems untouched, or without human interference  idea that most peat bogs have been damaged already and require management and restoration 

b i 8 0.0964 0.0093 3    ii A has greater richness  ORA B has greater evenness  ORA

iii stratified AND random (within each area)  idea that the number of samples within each area should be proportional to their size  correct suggestion for the number of samples taken within each area  3 ALLOW description of stratified e.g. 8 in conifer area, 24 in marshy area, 32 in grazed area c A because mean proportion of heterozygotes is higher  A = 0.898 AND B = 0.854 

ALLOW any correct number of significant figures and percentages

5 a i (in X) idea of no defined P phase  atrial fibrillation  idea of rapid or frequent electrical impulses in atria  idea of electrical impulses not only from SAN  idea of smaller gaps between QRS phases  ORA idea of heart rate set by SAN is faster  ORA 4 IGNORE references to T waves ALLOW Y has a defined P phase ALLOW Y does not show atrial fibrillation ALLOW idea of regular bursts of electrical impulses through atria in Y ALLOW electrical impulses only from SAN in Y Question Answer Marks Guidance ii 4570  cm^3 min-1^  3 Apply ECF ALLOW 4571 to 4572 ALLOW 1 mark for heart rate of 57.14 (allow 57.0 to 57.2) bpm ( full cycles in 4.2 seconds) if no other mark awarded b three cardiac cycles drawn  second cardiac cycle closer to the first cycle than the third cycle  abnormal QRS in second cycle (e.g. extended peak or lack of T phase)  2 e.g. 2 marks for

c (binds to) receptor in , cell surface / plasma , membrane  glycoprotein 

6 a idea that minimum period of darkness required for flowering is between 6.5 and 8.5 hours  idea that cockleburs flower when day length/period of exposure to light decreases  idea that red light prevents flowering  idea that far red light reverses/resets the effect of red light  idea that far red light reduces the period of darkness required for flowering 

ALLOW red light has no effect on flowering b ethene  1 c (named) chemicals  folding  stings  2 ALLOW 2 named chemicals Total 70