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Biology2 0 0 5 A S S E S S M E N T R E P O R T

Science Learning Area

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BIOLOGY

2005 ASSESSMENT REPORT

GENERAL COMMENTS

Student achievement in the 2005 Biology exam was similar to the results achieved in 2004. The

mean score for the 2005 examination was 56.7 %, which compares with previous means of 59.8%

(2004), 59.4 % (2003), 57.7 % (2002), 54.2 % (2001) and 53.7% (2000). The range of

examination marks was from 4 to 188 out of a possible 200.

The mean marks for Sections A, B, C, and D were 65.2 %, 54.0%, 66.9 %, and 44.9 %

respectively.

SECTION A: MULTIPLE-CHOICE QUESTIONS

Twenty six students scored full marks in Section A. The mean of facilities and range of facilitiesfor the each of the last five years are shown below. The facility for a question is the percentage of

students who gave the correct response.

Year Mean (%) Range (%)

2005 65.2 27 to 89

2004 71.2 24 to 90

2003 62.4 26 to 86

2002 59.4 20 to 86

2001 56.1 32 to 832000 57.9 24 to 95

It is the intention of the examination setters to produce multiple-choice questions that vary in

difficulty from easy knowledge through to difficult knowledge and problem solving. This

variation in question difficulty is reflected in the range in the question facility as seen in the table

above. Most questions are also intentionally discriminating so that, ideally, poorer students are

likely to choose the four responses with equal frequency, whereas more capable students will

show a distinct preference for the correct response. Data from the 2004 multiple-choice questionsshow that the top ten percent of the students preferred the correct response for every question,

whilst the bottom ten percent of students preferred the correct answers only for questions 4, 5, 7,

8, 9, 13, 14, 15, 16, 17, 19, 20, 21, 22 and 24.

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MULTIPLE-CHOICE ANALYSIS

The table below indicates the percentage of responses for each of the questions in Section A .

Question Percentage of Responses for Each Alternative

J K L M

1 9 7 71 12

2 27 50 13 10

3 21 6 67 6

4 6 77 8 10

5 15 5 23 57

6 25 7 4 65

7 71 10 14 5

8 2 3 25 709 79 7 8 6

10 17 68 10 4

11 29 19 7 45

12 13 18 34 34

13 6 80 5 8

14 83 2 7 8

15 10 6 77 7

16 12 12 65 11

17 4 83 7 6

18 15 54 14 16

19 34 46 12 7

20 1 9 14 75

21 3 6 85 6

22 82 6 6 7

23 10 30 17 44

24 3 89 2 5

25 8 5 54 33

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COMMENTS ON SELECTED MULTIPLE-CHOICE QUESTIONS

Question 2

This was the most poorly done question in Section A. While most students identified the shape of

receptors on the bacteria as essential for clumping to occur, only 27% of students recognised that

mutations in the bacterial DNA could alter the shape of the receptor and hence affect clumping.

Question 11

This question tested the understanding of the cell cycle. Almost half the students incorrectly

believed that all cells continue to divide. Less than a third of students identified that mitosis

would be blocked before mitosis began.

Question 12

In this data-analysis question, one third of students from all deciles incorrectly identified answer

L. This would indicate many students misread the question and identified the most consistent

rather than the inconsistent statement.

Question 19

While 80% of students identified fatty acids as components of lipids, a significant minority were

unable to recall that lipids are transported via the lymph vessels in the villi.

Question 23

The majority of students were able to identify most of the characteristics ofRandKselected

species. Less able students believed thatKselected species characteristically produced many

offspring throughout their lifetime.

Question 25

The majority of students identified that Set 1 was less accurate than Set 2. However, only the

more capable students were able to identify the greater scatter in Set 2, reducing the precision ofthe results for that set of data.

SECTION B: SHORT-ANSWER QUESTIONS

In general, 2 marks are allocated for one well-expressed piece of information. Questions that

require an explanation are worth 4 marks and therefore, in order to obtain full marks, students

must supply 2 relevant and connected pieces of information.

The mean mark for Section B was 52.9%. As with Section A, the examination setters aim to

produce short-answer questions that vary in difficulty from easy knowledge through to difficult

knowledge and problem solving. The mean mark for each question is shown in the table below.

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Question Mean Mark/Maximum Mark Mean Mark (%)

26 4.7/8 59.1

27 5.6/10 55.8

28 5.5/10 54.8

29 6.5/12 54.2

30 6.6/12 55.3

31 3.6/8 45.3

32 3.3/8 40.8

33 2.8/6 46.1

34 2.7/6 45.7

35 6.1/10 60.8

36 3.9/6 64.437 2.8/4 69.3

GENERAL COMMENTS

Many students fail to gain marks as a result of misinterpretation of questions. Students are

encouraged to read questions carefully so their responses are relevant to the question asked.

Many students ignore the instruction to give one fact or reason and give multiple answers.

Students are reminded that in this circumstance any single wrong answer will lose the

students all relevant marks.

A number of students rewrite or paraphrase the question. There are no marks for this andvaluable examination time is wasted through this practice.

Many students are sloppy in their use of biological language. Students who do not use

curriculum terminology correctly will be penalised.

Question 26

(a) A surprising number of students were unable to draw a suitable graph. Some graphs showedno increase in activation energy, while others altered the line for the reactants and products.

(b) The majority of students were able to explain activation energy. However, some answers

were vague or implied that the activation energy was the energy needed for the whole

reaction.

(c) Weaker students often achieved part marks by recognising that the enzyme lowered the

activation energy. Better answers referred to the enzyme inducing strain in the bonds of the

substrate molecules strain or aligning reactants to increase the rate of reaction.

Generally students handled this question well, using the term denature appropriately.

However, a significant minority of weaker students used a variety of other inappropriate

terms including describing proteins as dying, being destroyed, exploding or mutating.

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Students are reminded that correct use of terminology is critical to success in the

examination.

Question 27

(a) (i) Most students were able to link the DNA bands to greater similarity in DNA between

parents and offspring; however, weaker students failed to explain what should be

looked for when comparing DNA bands.

(ii) Most students correctly identified father 9.

(b) (i) Many students were able to state that PCR needs high temperatures to separate DNA

strands and that bacterial enzymes would not denature at high temperatures. Weaker

students often believed that whole cells, rather than extracted enzymes, were used in the

process.

(ii) This question was poorly answered. Only a small minority of students interpreted the

question correctly and identified the universality of DNA as the reason why bacterial

enzymes function on DNA from any species.

(iii) Only a minority of students correctly identified the role of the primer in determining the

start of the segment of DNA being copied. Many students confused the primer with

probes.

Question 28

(a) Few students received full marks for this question. Some students correctly identified the

relevant evidence but were unable to explain its significance. The best answers identified the

need for carbon dioxide when glucose was not present as the key piece of evidence and

explained that carbon dioxide was necessary for photosynthesis to produce the glucose

needed for respiration and hence survival. Students are advised that where multiple answers

are given to one question an incorrect statement will be penalised.(b) Students were generally able to answer this question successfully. However, weaker answers

failed to link increased photosynthesis with increased glucose production.

(c) A surprising number of students could not offer a specific result to indicate increased

photosynthesis. Better answers identified higher concentrations of oxygen or glucose

produced by cells with more of the chemical.

Question 29

(a) Most students identified the consequences of mitotic division. However, a significant

minority failed to recognise that the daughter cells weregeneticallyidentical and so failed to

gain full marks.

(b) While most students had some concept of the requirements for cell culture, many responses

were poorly expressed. Many weaker students referred to constant temperature and pH

without qualification. More able students qualified the factors (e.g., normal human body

temperature).

(c) Most students were able to identify the uncontrolled cell division of cancer cells as the

relevant factor in inducing cell division in the hybridoma cells.

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(d) Most students were able to identify that the lack of variation would adversely affect the plant

population if there were an environmental change. A weakness in many responses was to

specify that the environmental change must be detrimental.

Question 30

(a) Most students were able to successfully draw the next stage of mitosis. Common errors

involved not shading any chromosomes or showing all chromosomes as the same size.

(b) Few students correctly identified structures such as the spindle or linear chromosomes,

which indicated that this cell was eukaryotic. Many weaker responses stated that the cell was

undergoing mitosis but did not specify the evidence that led to this conclusion. A significant

number of students identified features of eukaryotic cells not evident in the diagram and

hence worth no marks (e.g., membrane-bound organelles or a nucleus.)

(c) Generally well answered. Students are reminded that misspelling of curriculum statement

terms such as cytoskeleton is penalised.

(d) (i) Most students correctly identified autumn as the season when meiosis occurred.

(ii) Answers to this question varied greatly in quality of expression. The best answers

identified that the fertilised eggs produced in autumn were the result of sexual

reproduction and hence showed variation, hence offspring produced asexually from

different eggs would show genetic variation. Weaker responses confused meiosis and

sexual reproduction.

Question 31

(a) Generally students were able to correctly identify exocytosis. A significant minority of

students were penalised for incorrect spelling of this curriculum statement term.

(b) While students showed an understanding of the structure of the cell membrane, very few

students correctly identified the fluidity of the membrane as the key feature for fusion ofvesicles.

(c) Students were generally able to describe the process of how a change in DNA altered a

change in the milk proteins produced.

Question 32

This was the most poorly answered question in Section B.

(a) Students needed to recognise the process occurring between M and N as fermentation in

yeast cells and then write a balanced equation using correct chemical formulae. Many were

unable to do this.

(b) This problem-solving question required students to understand that aerobic respiration

releases more energy than fermentation.

(c) Many students did not seem to understand that the energy released from respiration enables a

synthesis reaction to occur between ADP and P to form ATP. There is a common

misconception that ATP forms directly from glucose.

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Question 33

(a) Almost all students were able to use the information in the table to correctly state the

relationship between body mass and metabolic rate.

(b) Only the better students were able to relate the small size of the mouse to its large surface

area to volume ratio, and consequently its rapid rate of heat loss. It was more commonly

known that a higher metabolic rate would result in a higher rate of heat production.

Question 34

(a) General answers received very little credit. Students were required to be specific about how

the structural features of the nephron increased the rate of reabsorption. While many students

identified length of tubules increasing the surface area for exchange, surprisingly few were

able to identify thinness of the walls as affecting the distance for diffusion.

(b) Many students did not appear to link blood pressure with filtration.

Question 35

(a) Most answers correctly suggested inter-specific competition for resources. Other answers

were also possible.

(b) Almost all students were able to produce a table of some form. Marks were lost for

inaccuracies (it was commonly believed that rocky outcrops are a type of plant!) and for lack

of sufficient detail.

(c) As with all 4-mark questions, students were required to connect two well-made points in

answering this question. Most could deduce that the environment on Island M was more

similar to that of the mainland than Island L. Only the better answers went on to relate this to

selective pressures and the consequent effect on the gene pool of the birds. Common

misconceptions were that natural selection would not happen on M, and that speciation

would occur on L because other birds were present and interbreeding between species might

occur!

Question 36

(a) Most students were able to correctly state a relevant abiotic factor.

(b) It was widely known that the stores of starch would eventually be depleted. Better answers

also related the lack of leaves to a reduction in the rate of photosynthesis and the subsequent

effect on starch reserves.

Question 37

This was the most successfully answered question in Section B.

(a) Whilst this question was generally well done many students attempted to explain the reasons

for the relationship rather than simply describing it. Students often confused plant species

with plants.

(b) Most correctly stated a further decrease in diversity.

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SECTION C: PRACTICAL QUESTION

Question 38

(a) (i) Most students were able to write a testable statement linking pH to the rate of the

enzyme-catalysed reaction.

(ii) Answers to this question revealed a range of misconceptions. The most frequent answer

was that reducing the effect of random errors increased the accuracy of the data. This

answer received only partial credit. The accuracy of an experimental value indicates

how close the value is to the true value and depends on the extent to whichsystematic

errors are minimised.

(b) (i) Most students understood the importance of only having one independent variable in a

well-designed experiment.

(ii) The majority of students correctly stated substrate concentration as the independent

variable.

(iii) It is important that students answer the question they are asked. Students were requiredto describe the patternof the results, not to explainit. To gain full marks students were

required to correctly describe what happened to the rate of reaction as the substrate

concentration was initially increased and then as the concentration continued to

increase. Many students referred to the plateau in the graph, and used a variety of

spellings of the word to do so.

(iv) It was generally known that a lower temperature would decrease the initial rate of

reaction. However, many students thought that the rates of the reactions at different

temperatures would eventually be the same.

(c) (i) To gain full marks students were required to correctly select and label axes, use scales

that covered most of each axis, correctly plot the data points, and to draw a line of best

fit through the points. A common mistake was to extrapolate the line of best fit back tozero.

(ii) Students seemed to have a vague knowledge that systematic errors usually affect all of

the results in a consistent manner, but were not always able to indicate clearly how this

would impact on the pattern of results.

SECTION D: EXTENDED RESPONSE QUESTIONS

Each extended-response question is marked out of 15, with 12 marks being allocated for content

(each well-made point is worth 2 marks) and 3 marks for communication. Question 39 had two

content parts, with each part being marked out of six, whilst question 40 had three content parts,

with each part being marked out of four.

In awarding a communication mark the following factors were taken into account:

Is the response at least half a page in length and is it structured in the form of sentences and

paragraphs?

Does the response contain correct grammar and spelling?

Does the response clearly explain concepts using relevant and concise biological language?

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Students should be able to fully answer an extended-response question in about one page of

writing. It is unnecessary for students to re-write the question or to provide an introduction to

their response. Both of these practices are time wasting and receive no credit, and may even result

in a reduction in the communication mark.

Students continue to have difficulty expressing their ideas in a clear and well-organised manner.

Question 39

Most students showed a good understanding of the steps involved in the genetic engineering of

bacterial cells. However, many students failed to refer to the use of probes to locate the genes

involved and so failed to obtain full marks.

Many students had difficulty in successfully addressing the second dot point. To obtain full marks

for this section, students needed to make three points including at least one point addressing the

advantages of lifestyle change and one point addressing the advantages of genetic engineering.

Most students successfully made two points. Common arguments made for the benefits of

genetic engineering referred to effort, availability, and the lack of harm to animals. Some studentsmisinterpreted the question and described benefits of genetic manipulation of humans to prevent

disease, but these answers did not address the question and so failed to gain any marks. A large

number of students described in detail the changes in lifestyle that would decrease the risk of

acquiring lifestyle related diseases. However, they failed to state the advantages of changes in

controlling disease and so did not gain marks.

Question 40

Many students continued to show a poor understanding of the process of succession. In

addressing the first dot point many students referred to the fire as a selective agent, but failed to

specify particular changes in the environment that would alter the plant community. Better

responses identified the change in light intensity or nutrient concentration and the reducedcompetition as key factors in the difference in the community after the fire. Some students

misinterpreted the first dot point and discussed the process of succession, which was not relevant.

While some students were successfully able to describe the process of succession a significantnumber confused this concept with the concept of natural selection. Some students failed to gain

marks because they described animal succession rather than plant succession as required. The

better responses focused on colonising organisms changing conditions, thus suiting the

establishment of other species; these new species further changed conditions so that the

colonisers were no longer able to survive. The better students were also able to use a variety ofexamples to support their explanation.

Few students were able successfully to address the third dot point. Many students wrote detaileddefinitions of biodiversity, but these descriptions did not address the question and so earned no

marks. The better responses usually explained how interrelationships between species ensured the

stability of the ecosystem, and how biodiversity in the ecosystem can survive environmental

change.

Chief Examiner

Biology