2007 Biology Paper I Marking Scheme

8/4/2019 2007 Biology Paper I Marking Scheme

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2007 Biology

Marking Scheme

The marking scheme was prepared for markers' reference. It should not be regarded as a set of model answers.Candidates and teachers who were not involved in the marking process are advised to interpret its contents with care.The examination emphasises the testing of understanding, the practical application of knowledge and the use ofprocessing skills. Students are advised to study this document in conjunction with the examiner's comments oncandidates' performance inthis booklet.

Biology Paper 1

General Instructions1. For terms marked with '*', correct spelling is required.2. In questions asking for a specified number of reasons or examples etc. and a candidate gives more than that isrequired, the extra answers should not be marked. For instance, in a question asking for two examples to begiven and a candidate gives three answers, only the first two should be marked.

Guidelines for Assessing Effective Communication

4 parts from Section A and ipart from each question of Section B are chosen for assessing effective communication.A maximum of one mark can be awarded in each part. The mark scale below serves as a guide to markers for awardingmarks on effective communication.

Marks awarded Criteria on effective communication

Answers organised, clear, fluent and coherent. Ideas are accurately and conciselycommunicated to meet question requirements with no/little irrelevant material.Arguments/reasoning where required are logically, systematically and critically presented.Shows a good command of language, and is easy to understand.

Answers organised but lacking clarity and fluency. Ideas presented meet questionrequirements but contain some inappropriate use of words. Arguments/reasoning whererequired are acceptable but weak. Language used is understandable but with repetitionsand irrelevant material which sometimes blurs the main ideas.

o Answers disorganised and confused. Markers have to spend a lot of time and effort tolocate key points. Language used is almost incomprehensible with irrelevant materialburying the ideas required by the questions.


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MarksSection A

I. (a) virus .; .. ,.,' '., , , .. , , , ,(b) prokaryotes ..(c) fungi / protoctist ..(d) Protoctist I fungi .

Total: 4

2. (a) The water outside has a higher water potential than the cells of pears .water moves into the cells , , , ..,increasing the volume of the cell content / water content of the cell ..

As a result, more fruit juice can be extracted(b) The skin of the fruit acts as a barrier to water ..

Little / no water movement will occur .(c) The water / pear may be contaminated with pathogens / lead to food poisoning .

Total: 63. (a) Cell type X has no cellular content while cell type Y has." , .. , , .

Cell type X has a thicker cell wall than cell type Y "" .(b) (i) (1) Starch "."."., , ..(2) Add a drop of iodine solution to the leaf section "., .. , ..

Observe the leaf section under the microscope "." ,.".',., ' .The section turns blue black , , .. , , . , .. , , . , ' . ' ..

(ii)

1(c) When water evaporates from cell type Y, a transpiration pull is set up .

Water is drawn from xylem to cell type Y .together with dissolved minerals .

Total: 12+1

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Marks4. (a) 130 .

(b) correct title (D \t 2correct labelling of axes (A) '" 1 I z , I I zcorrect drawing and labelling of bars (B) ;.... 1Y ze.g. Title: Activity of three bands of yeast

Brand BDifferent brands of yeast

(c) Anaerobic respiration of yeast .produce carbon dioxide ..which is trapped inside the dough .

making it rises

BrandA Brande

I Effective Communication (C) (/) I(d) Brand B ..(e) To ensure the temperature of the three mixtures are the same / maintain the temperature at 30C

throughout the investigation '" ..(0 Use only one brand of yeast '" '" '" ..

Put the measuring cylinder in water baths at different temperatures ..Total: ] 1+1

5. (a) Yes.To produce offspring with different phenotypes .there must be two different combinations of gametes '"Therefore, either one of the parents must be heterozygous, producing two types of gametes carrying

different alleles .

ORThe parents are of different phenotypes, hence, one of the parents must be homozygous recessive .To produce offspring with different phenotypes .the other parent must be heterozygous, producing two types of gametes carrying different alleles .

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Marks(b) Individual I possesses straight little fingers, she must be homozygous recessive. .. .. . 1and pass an allele for straight little fingers to individual 4 . . 1Individual 4 possesses bent little fingers, she must have at least one allele for bent little fingers....... IHence, individual 4 is hetero ous .. . .. .. .. .. .. . .. I

E ective Communication C 1(c) Define symbols (S) .Let B be the allele for bent little fingersand b be the allele for straight little fingers

Individual 5 x Individual 6Parent bb Bb

~Gamete b B b

Offspring Bb bb(bent little fmger) (straight little finger)Deduct 1marker for wrong format, e.g. no identification of parent, gamete or offspring,or no line indicatin the combination of amete.The probability for their child to have straight little finger is V : ! 1 0.5 I 50% .Total: 12+1

6. (a) (i) Gastric juice is acidic I contains hydrochloric acid .(ii) Pancreatic juice I bile / intestinal juice inthe small intestine... . .. .. .. 1are alkaline I

1

(b) After meal, the release of gastric juice increases 1and the pressure inside the stomach increases IAlso, the stomach and oesophagus are at the same level while sleeping . .. .. .. . 1These increase the chance of gastric reflux(c) The acid in the gastric content dissolves .the enamel! calcium salts of the tooth 1

Total: 9+1

Section B7. (a) (i) (1) * ciliary muscles .

(2) When the man is looking at a near object, the weakened ciliary muscle contract withless force 1and the tension of the suspensory ligament remains high....... .. .. . . .. .. . .. 1Hence, the lens is not thick enough ' Iand fails to conver e Ii t to form a clear ima e on the retina. . .. .. .. . .. . . .. .. .. .. .. .. .. .. I

(ii) The lens becomes less elastic I cloudy .

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7. (b) (i)

8. (a) (i)

Marks(iii) Layer B contains light sensitive cells . .. . .. .. . .. . .. . .. . . .. . .. .. 1

cannot obtain nutrients / oxygen from layer C 1+As a result, light sensitive cells die .. . . .. ILight falling on layer B cannot be detected Ino nerve impulse can be produced 1

Therefore the vision is impaired Total: 10+/

Genetic variations exist among the bacteria in their resistance against the antibiotic .The increase in the amount of antibiotics kills non-resistant form while the resistant form

survive '" IThe resistant form continue to reproduce / produce more of its own kind 1The number of resistant form of bacteria increases faster..................... 1

(ii) Any group with weak immune system plus correct example, e.g, children, elderly, AIDSpatients, cancer patient after treatment, patients taking immunosuppressor drugs 2(Accept other reasonable answers)

(iii) Prescribe antibiotics only when necessaryInstruct the patient to finish the whole course of prescriptionUse narrow spectrum antibiotics

any two 1,1Total: 8

R: * filament '" '"S: * ovary Iovule '" " '" ..

(ii) Insect pollination Large I brightly coloured petal Anther I stigma located inside flower } any two .. Presence of insect guidePollen grain develops to form a pollen tube... . . . '" .Pollen tube carries the male gametes .down the style to the ovary / and digests the tissues of the style .and releases the male gametes into the ovule '" ..

II1I

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(iii)

(vi) Vegetative propagation 1Total: 10

8. (b) (i) Glucose consumption increases during exercise .because glucose is used in respiration J respiration rate is faster .to provide more energy for muscle contraction ..

(ii) More glucagon is released during exercise '" . . . Iwhich stimulates the conversion of glycogen to glucose in liver .. . .. . .. .. .. .. 1to restore the blood lucose level f com ensate for the increase in Iucose consum tion ]

E ective Communication C 1(iii) Trends:

Increase during exercise .Decrease after exercise '" " , '"

Total: 8+/

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Marks9. (a) (i)

1(ii) Bacteria break down the organic matter to inorganic matter '" , " .

which is then absorbed and used by algae for growth .(iii) The biomass of algae is limited in the ecosphere '" '" .

Energy is lost along food chain '" " .and cannot support more trophic levels

Total: 8+1

9. (b) (i) Whole milk has more fat than fat-free milk .Presence offat slow down the digestion of carbohydrates ..and hence a slower absorption of glucose '" .

(ii) Diabetics cannot lower their blood glucose level if it is too high '" .Oatmeal has a low GI value f causes a slow rise in blood glucose level '" ..Therefore, oatmeal is better than corn flake .

(iii) The overall energy intake should be less than the overall energy expenditure. . . . 1so that the food reserve will be mobilized and used . . . .. . . . . .. . . . .. . . . . .. . . . .. . .. . . . . .. . .. . . . .. .. IThe diet should contain sufficient amount and types of nutrient , . . . . . . . . . . . . .. 1for proper functioning of the body '" '" ..

Total: 10

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2007~. 9=2007 Biology Paper 1

uestion No. Key Question No. Key1. A (65) 31. D (42)2. C (62) 32. "A (86)3. C (58) 33. C (47)4. D (95) 34. B (67)5. A (57) 35. C (74)6. A (84) 36. *7. B (51) 37. C (65)8. e (88) 38. B (65)9 . C (81) 39. 0 (37)10. 0 (45) 40. A (56)II. B (71) 41. D (74)12. C (48) 42. A (62)13. B (81) 43. A (47)14. c (32) 44. D (81)15. n (57) 45. B (59)16. A (38) 46. D (29)17. D (47) 47. B (28)18. B (91) 48. B (59)19. 0 (45) 49. C (37)20. D (84) 50. 0 (29)21. A (60) 51. A (66)22. D (47) 52. B (98)23. C (76) 53. C (89)24. A (96) 54. B (89)25. C (91) 55. B (27)26. A (49) 56. C (90)27. B (81) 57. A (70)28. A (56) 58. B (81)29. C (60) 59. C (92)30. 0 (88) 60. A (70)

* ; ; $ : ~ l i iH J t f f i I l J ~ This item was deleted.ft: !i5lf!pglf*~!f!;tEifJl$I'N ote : F ig ure s in b ra ck ets in dic ate th e p erc en ta ge s o f c an did ate s c ho osin g th e c orre ct a nsw ers.

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Candidates' PerformanceBiology Paper IThis paper continues to include a wide variety of question types and contains a number of questions set on newtopics of the curriculum introduced in 2003. Situations encountered in daily life are used to provide contexts forassessing candidates' ability to apply biological concepts and principles in problem solving. There are alsoquestions assessing candidates' ability to analyze given data, make logical deductions, and provide reasonablesuggestions to explain observations.Markers considered the paper appropriate with regard to the level of difficulty and balanced in terms of syllabuscoverage.The following table shows the general performance of candidates on different questions and the popularity of thequestions in Section B:

Question No. Popularity (%) Performance in General1 Fair2 Fair

Section A 3 Satisfactory4 Compulsory Good5 Poor6 Satisfactory7 71% Satisfactory*Section B 8 66% Good9 62% Fair

* A choice of2 out of3 questions,Candidates' performance on individual questions:Section AQ.l This question required candidates to make use of the information provided and classify the specimen

accordingly. Some candidates could not use their knowledge in characteristics of different groups of livingorganisms to process the information. They had little idea on the relative sizes of different groups oforganisms. A tot of them could give the correct grouping but spelt the group name wrongly.

Q.2 (a) Most candidates recognized the question was set on the application of osmosis to a daily lifesituation and gave a proper explanation.

(b) Many candidates could not give the correct term for the skin of the fruit. They mixed it up withcell wall. Some were not aware that the skin of the fruit has the protective function against waterloss by being nearly impermeable.

(c) Most candidates could suggest related hygienic problems. Some failed to use accurate words todescribe the suggested problems, saying that 'the pear may be infected by bacteria' or 'the pearmay be polluted' .

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Q.3

QA

Q.5 (a)

(a) This part was generally well answered but some candidates gave answers on the arrangement ofcells like closely packed, instead of the structural differences between the two cell types.

(b) 0) (1) Well answered.

(2) Only a few candidates could give a correct answer to the question. Mostcandidates did not address the question and put down the test for starch in awhole leaf while a thin section of the leaf was the subject tested in the question.

(ii) Many candidates scored well in this question. Some candidates, however, failed to statethe conversion of the stored carbohydrate into other forms before it is used Ort ransported .away. Quite a number of candidates simply mentioned that the stored carbohydrate wasused for growth without referring to the process of respiration.

(c) Many candidates could not link up the transpiration stream and the uptake of mineral salts by thecells in the leaf; they merely described the stream and the uptake of mineral salts in the rootsseparately.

(a) Well answered.(b) Many candidates could not write a proper title for the bar chart and a few drew histograms instead.(c) Some candidates could not specify that anaerobic respiration occurs and the rising of the dough is

caused by the accumulation of carbon dioxide released which is trapped inside the dough.(d) This part was generally well answered. Only a few candidates took yeast as an enzyme and

wrongly stated that the warm water bath provides an optimum temperature for enzyme reactionrather than controlling the temperatures in the experiment.

(e) Good performance. Most candidates could suggest a workable design for the study.

Many candidates agreed with the conclusion but only very few candidates could relate the roles ofgametes with inheritance. Most of the candidates could not clearly explain the necessity of havingtwo different gametes produced from either one of the parents so as to produce offspring withdifferent phenotypes. This question would therefore differentiate candidates who could make useof fundamental knowledge on genetics to produce logical reasonings from those who could onlyrecall stereotyped answers.

(b) Satisfactory performance. However, some candidates just gave some stereotypical butincoherently presented answers. This reflects that they lacked an understanding of the logicaldeduction leading to the development of the argument.

(c) This part was essentially a traditional genetic problem. However, quite a number of candidatescould not construct a genetic diagram using the correct format, nor could they clearly define thesymbols used. Some failed to determine the genotype of individual 6 and consequently gave twogenetic diagrams.

Q.6 (a) (i) & (ii)These parts were well-answered. It shows that the candidates appreciate the applicationof biological knowledge in daily issues. Candidates were able to suggest how thedamage of the oesophagus occurs and how the small intestine is protected. Yet, quite anumber of candidates wrongly stated that bile salts were alkaline and could neutralize theacidic chyme from stomach.

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(b) Most candidates could relate the increasing chance of gastric reflux with the increased secretion ofgastric juice and the increased pressure inside the stomach. Only a few candidates could correctlyrelate the lying down posture with the backflow of gastric content to the oesophagus. Somesimply stated that it is easier to have gastric reflux after sleeping without providing anyexplanation.

(c) Inaccurate or imprecise terms such as 'damage', 'destroy' and 'digest' were used to explain theaction of the acidic content on the enamel.

Section BQ.7 (a) The performance was good in general.

(i) (1) Most candidates could identify structure A correctly but misspelt the word'ciliary'. A few candidates took it as the suspensory ligament.

(2) Some candidates just recited the focusing mechanism of looking at a nearbyobject by a normal person as the answer. They failed to address the question bydeducing the consequences of the weakening of structure A. Some failed to givethe precise description of the formation of image; they simply stated that theimage could not be focused.

(ii) Well answered.(iii) Many candidates only mentioned that layer C can absorb light to reduce reflection of

light inside the eyeball and missed out the function of providing nutrients and oxygen tolayer B. Some wrongly stated that image cannot be formed instead of not being detectedby the retina while some thought that the image will be formed on layer C after thedetachment of layer B.

(b) The performance on this question was fair.(I) Many candidates thought that the increasing use of antibiotics will act as a mutagen to

cause the occurrence of the resistant form of the bacteria. They did not appreciate therole of antibiotic as a selective agent in the process of evolution. Some candidates stillheld the misconceptions that the bacteria become more and more resistant to theantibiotics and were not aware that the resistant form exists at the very beginning. Quitea number of candidates misinterpreted the question and wrongly suggested that bacteriawere able to produce antibodies against antibiotics and develop a memory of it.

(ii) Most candidates gave sensible suggestions supported with a full explanation.(iii) Some candidates suggested that the reduction of dosage of antibiotics used would slow

down the rise of resistant forms of bacteria. Some simply gave answers related to generalhealth rather than the specified context, e.g. 'do more exercises' or 'have enough rest'.

Q.8 (a) Well answered in general.(i) Most candidates correctly identified the structures. However, some candidates could not

distinguish stamens from filaments or anthers. Some also had difficulty in identifyingstructure S with reference to the location where the section was cut.

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(ii) Mostcandidates could state the method of pollination correctly. A few candidates couldnot distinguish self- or cross-pollination from insect or wind pollination. Somecandidates gave features that are not observable from the photomicrograph, e.g. thepresence of nectar.

(iii) The performance on this part was fair. A few candidates still took pollen grains as themale gametes. Some failed to list the events in the correct order.

(iv) Some candidates wrongly stated that self pollination is a kind of asexual reproduction.(b) The performance on this question was satisfactory in general.

(i) Quite a number of candidates simply mentioned that the body needs more energy butfailed to mention that glucose is used in respiration for releasing energy. Some alsofailed to state the energy is used for muscle contraction.

(ii) Many candidates confused the terms 'glycogen' and 'glucagon' and gave wrong spellings.The action of glucagon is first introduced in this curriculum, yet some candidates stillregurgitated answers from past papers of the previous curriculum and included thedecreased secretion of insulin instead. Treating glucagon as an enzyme which has adirect effect on glucose was still common.

(iii) Well answered.

Q.9 (a) The performance on this question was fair.(i) Candidates could only give answers with discrete points and failed to give an overall

view of the role of producers in a self-sustainable ecosystem, i.e. to maintain thecomposition of gases in the atmosphere and to act as energy transformer at the base ofthefood pyramid.

(ii) The role of bacteria as the decomposer to recycle minerals was not well understood bythe candidates.(iii) Most candidates could identify the energy loss along the food chain as the reason but they

were unaware of the fact that the energy captured by the algae in the ecosphere is limited.(b) The performance on this question was fair.

(i) Candidates could point out that the difference in the two types of milk lies in the absenceof fats in fat-free milk and presence of fat in whole milk. They failed to go further topostulate the presence of fats may slow down the digestion of carbohydrates orabsorption of glucose that will lead to a lower GL

(ii) Most candidates could make the right choice but failed to relate clearly to the inability oflowering the glucose level in diabetic person. Some answered that diabetic personsdischarge urine with glucose, which only occurs when the glucose level is too high.

(iii) While in the planning of a healthy, weight reduction diet, very few candidates couldmaster the underlying principles of energy deficit for weight loss and a balanced diet formaintaining health. Hence, they failed to give a complete answer.

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General comments and recommendationsThe pe~ormance on this paper showed that candidates could do well in more conventional questions which askedfOT.stralghtforw~d answers. The performance on questions that demands high order thinking skills was lesssatisfactory, e.g. m Q.5 (a), Q.7 (b) (i),Q.9 (a) (i), and Q.9 (b) (i) & (iii).The m.astery of new ~opics in the curriculum was still weak. It was further noticed that some candidates simplyre~rglt~ted t?e marking schemes of past papers which are irrelevant to the contexts given in the questions. This wasevident Intheir answers to Q.3 (b) (i) (2), QA (e), Q.5 (a) & (b), Q.7 (a) (i) (2), Q.7 (a) (iii) , Q.7 (b) (i) and Q.9 (i).Ana!ysis .of the candidates' response to novel contexts revealed that some candidates lacked genuine understandingof bl~loglcal concepts. Mechanical drilling of past papers is not recommended. More time should be spent on thelearning of the fundamentals.Spelling. err?rs were ~till prevalent. Writing correct biological terms are essential to the study of biology andcommurucation. ~andldates' skills in interpreting photomicrograph and photograph need improvement and thiscould only be achieved through more observations done in the laboratory and field studies. '

Paper 2There were 60 questions in this paper. The overall performance of candidates this year was quite good. The meanscore of candidate was 38. The following items serve to reveal some of the common weaknesses ofthe candidates:

43. Mikania micrantha C f f 1 : l 1 i I D is a plant that grows rapidly on the neighbouring plants, thus reducing theamount of tight that reaches them. Its relationship with the neighbouring plants is

.A.S.C .D.

competition.mutualism.parasitism.predation.

(47%)(7%)(44%)(2%)This question reflects that more than half of the candidates held a vague concept about the relationship of organismsin an ecosystem. They simply judged the relationship by beneficial or harmful effects but failed to note that there isno close association between Mikania micrantha and the neighbouring plants. Also, they overlooked the fact thatone species can outcompete another in a competition.

Directions: Questions 46 and 47 refer to the diagram below, which shows a diagrammatic representation ofthe root and the leaf of a herbaceous plant:P Q R~r o - - - - - ~ (1)Fr) ~

1 : _ ---(2),

( 3 ) ~ : : : : : : : : ~tF1P 1146. The direction of carbon dioxide diffusion between the plant and the surroundings under bright daylight isindicated by

A.S.c... D.

(1) only.(2) only.(I) and (3) only.(2) and (3) only .

(10%)(51%)(10%)(29%)

Although the majority of the candidates knew that there was a net release of carbon dioxide out of the leavesthrough the stomata under bright daylight, about two-thirds of them overlooked the point that carbon dioxide wasalso released from the root as a product of respiration.12


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47. Which cell type(s) is / are important for supporting the plant?A .

*B.C.D.

PonlyP and QonlyQand RonlyP, QandR

(59%)(28%)(3%)

(10%)The majority of the candidates were aware of the rigidity of P offering support to a herbaceous plant. However,only the one-third of them realized that the turgidity ofQ also played a significant role in supporting the leaf.

Directions: Questions 49 and 50 refer to the diagram below, which shows the structure of a nephron.

49. Which region of the nephron has cells with the greatest number of mitochondria?A.B.*c.D.

1234

(6%)(7%)

(37%)(51%)

This question required candidates to relate the processes taking place at different regions of the nephron to energyexpenditure, and hence deduce which region contains cells with the greatest number of mitochondria. The majorityof the candidates chose region 4 as the answer without considering that the process taking place there is ultra-filtration which is a purely physical process caused by the high pressure built up at the glomerulus. Indeed, thereabsorption at region 3 requires energy supply from mitochondria. This reflected that candidates were weak inintegrating knowledge from different topics.

2007 Biology Paper I Marking Scheme

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