Cambridge International AS & A Level Biology Paper 4 Theory Answers (May-June).pdf, Exams of Biology

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Cambridge IGCSE™

BIOLOGY 0610/

Paper 4 Theory (Extended) May/June 2023 PROVISIONAL MARK SCHEME Maximum Mark: 40

PRE-STANDARDISATION

Cambridge Assessment International Education – Generic Marking Principles

These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these marking principles. GENERIC MARKING PRINCIPLE 1: Marks must be awarded in line with:

• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question the standard of response required by a candidate as exemplified by the standardisation scripts. GENERIC MARKING PRINCIPLE 2: Marks awarded are always whole marks (not half marks, or other fractions). GENERIC MARKING PRINCIPLE 3: Marks must be awarded positively :
• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the question as indicated by the mark scheme. The meaning, however, should be unambiguous. GENERIC MARKING PRINCIPLE 4: Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level descriptors. GENERIC MARKING PRINCIPLE 5: Marks should be awarded using the full range of marks defined in the mark scheme for the question (however ; the use of the full mark range may be limited according to the quality of the candidate responses seen).

PRE-STANDARDISATION

GENERIC MARKING PRINCIPLE 6: Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or grade descriptors in mind. Science-Specific Marking Principles

1. Examiners should consider the context and scientific use of any keywords when awarding marks. Although keywords may be present, marks should not be awarded if the keywords are used incorrectly.
2. The examiner should not choose between contradictory statements given in the same question part, and credit should not be awarded for any correct statement that is contradicted within the same question part. Wrong science that is irrelevant to the question should be ignored.
3. Although spellings do not have to be correct, spellings of syllabus terms must allow for clear and unambiguous separation from other syllabus terms with which they may be confused (e.g. ethane/ethene, glucagon/glycogen, refraction/reflection).
4. The error carried forward (ecf) principle should be applied, where appropriate. If an incorrect answer is subsequently used in a scientifically correct way, the candidate should be awarded these subsequent marking points. Further guidance will be included in the mark scheme where necessary and any exceptions to this general principle will be noted.
5. ‘List rule’ guidance (see examples below) For questions that require n responses (e.g. State two reasons…):

• The response should be read as continuous prose, even when numbered answer spaces are provided
• Any response marked ignore in the mark scheme should not count towards n
• Incorrect responses should not be awarded credit but will still count towards n
• Read the entire response to check for any responses that contradict those that would otherwise be credited. Credit should not be awarded for any responses that are contradicted within the rest of the response. Where two responses contradict one another, this should be treated as a single incorrect response.
• Non-contradictory responses after the first n responses may be ignored even if they include incorrect science

PRE-STANDARDISATION

6. Calculation specific guidance Correct answers to calculations should be given full credit even if there is no working or incorrect working, unless the question states ‘show your working’. For questions in which the number of significant figures required is not stated, credit should be awarded for correct answers when rounded by the examiner to the number of significant figures given in the mark scheme. This may not apply to measured values. For answers given in standard form, (e.g. a x 10n) in which the convention of restricting the value of the coefficient ( a ) to a value between 1 and 10 is not followed, credit may still be awarded if the answer can be converted to the answer given in the mark scheme. Unless a separate mark is given for a unit, a missing or incorrect unit will normally mean that the final calculation mark is not awarded. Exceptions to this general principle will be noted in the mark scheme.
7. Guidance for chemical equations Multiples/fractions of coefficients used in chemical equations are acceptable unless stated otherwise in the mark scheme. State symbols given in an equation should be ignored unless asked for in the question or stated otherwise in the mark scheme.

PRE-STANDARDISATION

Examples of how to apply the list rule State three reasons…. [3] A B (4 responses) C (4 responses) D (4 responses) E (4 responses)

1. Correct 
2. Correct  2
3. Wrong 
4. Correct, Correct , 
5. Correct  3
6. Wrong ignore
7. Correct 
8. Correct, Wrong ,  2
9. Correct ignore
10. Correct 
11. Correct, CON (of 2.) , (discount 2) 2
12. Correct 
13. Correct 
14. Correct  3
15. Correct, Wrong 

F

(4 responses) G (5 responses) H (4 responses) I (4 responses)

1. Correct  2
2. Correct 
3. Correct CON (of 3.)



(discount 3)

1. Correct  3
2. Correct 
3. Correct Correct CON (of 4.)



ignore ignore

1. Correct  2
2. Correct 
3. CON (of 2.) Correct (discount 2) 
4. Correct  2
5. Correct 
6. Correct CON (of 2.)



(discount 2) Question Answer Marks Guidance

PRE-STANDARDISATION

1(a)(i) B ; 1 (a)(ii) C ; 1 (a)(iii) A D E ; 1 (a)(iv) separates the left side and the right side of the heart ; keep deoxygenated blood and oxygenated blood separate ; AVP ; 2 Ignore ref to septum e.g. to allow efficient transfer of oxygen ; (a)(v) blood flows through the heart twice (in one circuit of the body) ; there are two separate blood circuits / pulmonary circuit and systemic circuit ;

(b)(i) arterioles ; 1 (b)(ii) (change in pressure) caused by contractions of muscles of the heart / ventricle ; pumping blood through the arteries ; 2 Ignore left / right (b)(iii) arteries: thick wall to withstand the high blood pressure ; wall contains, muscular/elastic tissue, to stretch and recoil ; muscular / elastic, tissue maintains blood pressure ; (relatively) narrow lumen maintains (high) blood pressure ; veins: thin walls to carry blood at low pressure ; (relatively) large lumen to provide less resistance for blood flow / AW (at low pressure) ; large lumen to carry larger volume of blood ; valves to prevent backflow (caused by low pressure) ; 4 max three from artery or vein Must say which blood vessel they are referring to. If no blood vessel specified assume they are talking about arteries

PRE-STANDARDISATION

Question Answer Marks Guidance 2(a) test-tube A no enzyme / amylase present to breakdown the starch ; Benedict’s solution remains blue in the absence of maltose / reducing sugar ; test-tube B amylase breaks down the starch ; into maltose ; maltose is, a small molecule / soluble ; maltose is able to pass through the dialysis tubing (into the water) ; by diffusion ; from a region of high concentration to a region of low concentration ; Benedict’s solution turns red in the presence of maltose / reducing sugar ; 6 max 5 from test-tube B (b) pepsin protein amino acids / peptides 4 1 mark for each correct row A polypeptides for protein lipase fats / oils / lipids fatty acid and glycerol trypsin protein amino acids / peptides maltase maltose glucose ;;;; (c) villi / microvilli ; 1

PRE-STANDARDISATION

a Question Answer Marks Guidance 3(a)(i) flowering plants ; dicotyledons ; 2 Accept angiosperms Accept dicots (a)(ii) any two from: one seed leaf / one cotyledon ; parallel veins ; adventitious roots ; flower parts in multiples of three ; vascular bundles throughout stem ; strap-shaped leaves ;

(b)(i) 600 ; 1 (b)(ii) meiosis ; reduction division / chromosome number is halved ; from diploid to haploid ; producing genetically different cells ;

(b)(iii) fertilisation ; 1 (c)(i) a group of organisms that can reproduce ; to produce fertile offspring ;

(c)(ii) anther correctly labelled^ ;^ stigma correctly labelled ; arrow drawn from anther to the stigma ;

R if arrow starts and finishes on the same flower

PRE-STANDARDISATION

(c)(iii) X drawn on any ovule ; 1 Question Answer Marks Guidance (c)(iv) any three from: reliant on (named) pollinators ; reliant on, environmental conditions / wind ; idea of wastage of pollen ; idea of more energy required to produce more pollen ; more than one plant required ; risk of less, fertilisation / reproduction ; 3 Vetter comment: I was not sure whether I was explaining the disadvantages compared with asexual reproduction, or with self-pollination. May need to consider asexual reproduction? Question Answer Marks Guidance 4(a)(i) any four from: ref to translocation ; carbohydrates / glucose / sugars / amino acids, made in the leaves ; leaves act as a source ; substances travel between sources and sinks ; transported in the phloem as sucrose ; to the roots which act as a sink ; girdling cuts the link between the source and sink ; sucrose / sugars, collect above the girdle ; AVP ;

Vetter comment: is this the only term accepted? Does it need to be underlined? Vetter comment: Is ref to leaves/roots in place of source/sink accepted? references to creating differences in osmotic potential

PRE-STANDARDISATION

(a)(ii) xylem is still intact ; mineral ions transported by xylem ;

Question Answer Marks Guidance (b) any three from: glucose required for (aerobic) respiration ; respiration releases energy ; energy required for active transport ; to transport mineral ions against their concentration gradient ;

(c) 6CO 2 + 6H 2 O → C 6 H 12 O 6 + 6O 2 ;; 2 1 mark for formula 1 mark for balancing

PRE-STANDARDISATION

Question Answer Marks Guidance 5(a) contains (a group of) receptor cells ; that are sensitive to, light / specific stimuli ; 2 Ignore the definition of organs in general (b) brain ; spinal cord ; 2 in either order (c)(i) blind spot labelled ; 1 (c)(ii) retina H contains, receptor cells / rods and cones 3 1 mark for each correct row Accept receive light (stimulus) for H Vetter comment: would you accept protection from dirt for D? optic nerve G transmits impulses to the central nervous system cornea D refracts light / allows light through the eye ;;; (d) circular muscle and radial muscle ; 1 in either order (e) any three from: ciliary muscles relax ; suspensory ligaments remain slack (as they are overstretched) ; lens, is not stretched / remains wide ; angle of refraction remains unchanged / AW ;

Question Answer Marks Guidance

PRE-STANDARDISATION

6 (a) plasmid ; restriction ; sticky ; gene ; (DNA) ligase ; recombinant (plasmid) ; asexual ;

(b) any two from: reproduce rapidly ; no ethical issues ; ability to make complex molecules ;

(c) any three from: additional nutrient content may be (too) small ; seeds may be expensive to purchase ; unknown health risks to consumers ; risk of cross-contamination with wild rice ; reduction in biodiversity / genetic diversity ; consumers may reject products that have been genetically modified ; AVP ;

(d) scurvy – vitamin C ; rickets – vitamin D / calcium ;

Accept magnesium