1 GCE Biology A Advanced Subsidiary Unit H020/02 Depth in biologyReviewing the External Assessment (RTEA) GCE Biology A Advanced Subsidiary Unit H020/02 Depth in biology Reviewing the external assessment from June 2016
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3 Introduction The aim of the presentation is to show which parts of the summer 2016 Depth in biology H020/02 exam were done well and which were done poorly. We shall discuss reasons for varying candidate performance from question to question and consider techniques to improve future candidate performance. It was pleasing to see that most candidates attempted all the questions and could answer questions on a wide range of topics. However, candidates differed in their ability to translate their knowledge into marks, and we will look at the common mistakes which were seen on this paper, such as the failure of some candidates to focus their answers on the question being asked. Please have a copy of the June 2016 H020/02 Depth in biology paper and mark scheme to hand in order to get the most out of the presentation.
4 Introduction June 2016 saw the first live assessment of the new linear AS Biology courses. The reformed assessments differ to the legacy qualifications in a number of areas. The key differences are, Linear not modular Assessment Objectives and weighting altered Practical weighting of 15% Mathematical weighting of 10% Inclusion of Multiple Choice Questions (MCQs) The use of Level of Response (LoR) mark schemes for some extended response questions. The new Depth in biology H020/02 examination includes the use of Level of Response (LoR) mark schemes for questions 4(c) and 5(b).
5 Assessment objectivesLegacy AO1 AO2 AO3 Recognise, recall, show understanding; select, organise, communicate information Analyse and evaluate Apply knowledge to unfamiliar situations Assess information Demonstrate practical, make observations, evaluate methodology New AO1 AO2 AO3 Demonstrate knowledge and understanding of ideas, processes, techniques and procedures Apply knowledge and understanding (theory, practical, qualitative and quantitative data) Analyse, interpret and evaluate information, make judgements, develop and refine practical
6 Assessment objectives – weightingsAS Levels AO1 AO2 AO3* Legacy 38 40 22 New 35-40 40-44 20-23 * Note: The majority of AO3 was previously assessed in the coursework unit (F213), but is now assessed entirely by written examinations What do the changes to the assessment objectives mean? Less recall Practical contexts More new information contexts in which to apply knowledge / understanding data / information to evaluate / interpret
7 Assessment Objective 1 Demonstrate knowledge and understanding of scientific ideas, processes, techniques and procedures Most candidates learn facts thoroughly and are able to gain marks on questions that test Assessment Objective 1. This new AS specification paper has fewer questions that depend on straightforward recall and the context of these questions can be unfamiliar. AO1 questions can include knowledge of practical procedures, such as the use of a spirometer in question 1(b)(ii).
8 Assessment Objective 2 Apply knowledge and understanding of scientific ideas, processes, techniques and procedures: in a theoretical context in a practical context when handling qualitative data when handling quantitative data Candidates do not always perform as well with questions testing application of knowledge. Candidates need to read the question carefully, and take time to think about how the new context links with the content they have learnt, before commencing writing. There is a greater mathematical content in the new AS specification being tested by AO2 questions. It is also worth noting that candidates who learn mark schemes from previous examinations fail to pick up many marks on AO2 questions. 8
9 Assessment Objective 3 Analyse, interpret and evaluate scientific information, ideas and evidence, including in relation to issues, to: make judgements and reach conclusions develop and refine practical design and procedures Candidates again tend to find AO3 questions more challenging than recall. Question 4 involved evaluating information from a results table and analysing a practical procedure and few candidates scored maximum marks here. 9
10 Question 1(a)(i) Generally very well-answered. Candidates needed to identify the correct diagram (a) before they could score. This answer gains full marks and has given the three key differences between the two diagrams. There were a number of ways to express the relaxed diaphragm including domed, curved up, higher, not flat. Candidates stating that the lungs were ‘empty’ did not gain credit and it is clear from the diagram that this would not be the case.
11 Question 1(a)(ii) Candidates who failed to score here either confused the term passive with processes that occur without conscious thought or, as in this case, referred to energy without continuing their answer to explain why energy was not required. Surprisingly, very few candidates explained that the lungs were elastic and would therefore recoil. The most common correct answer was the first option on the mark scheme: muscle relaxation. 11
12 Question 1(a)(iii) Candidates did not often use correct scientific terminology when answering this question. Correct terms such as inhalation, exhalation, bronchioles and bronchi should be used. This candidate has been awarded mark point 1 for their first statement. They then use more vague terminology such as air ‘flowing’ and ‘moving’ where they should have talked about inhalation and exhalation. Very few candidates were able to state that there would be more resistance to inhalation. 12
13 Question 1(b)(i) Many candidates scored well on this question gaining all four marks. E, the expiratory reserve volume, was a common error for residual volume as shown in this example. It is worth noting that this candidate has clearly crossed through their initial answer for vital capacity and then written their answer separately. Some candidates attempt to modify letters by writing over the top of their first answer. However, this will result in no mark being awarded as it is not clear which letter has been written. 13
14 Question 1(b)(ii) This was generally a very well answered question. Candidates should expect to be questioned on their practical experience in written examinations. This candidate has gained marks by using the term ‘possible’ on both inhalation and exhalation. This makes it clear that the inhalation and exhalations are both maximum. Some candidates only gained one mark on this question by describing breathing out before breathing in, despite the help given with this on the graph. 14
15 Question 2(a) Very few candidates scored full marks on this question. Two marks were available for correctly completing the top table with one mark if two out of the three ticks were correct. One mark was available for a correct second table. Some candidates placed two ticks in one row despite the clear instruction for ‘a’ tick. This candidate shows the most common incorrect answers. Candidates could be given credit for identifying A as either mitosis or meiosis as, although the reduction division would occur at this point, candidates may have expected it to occur at the previous stage. Many candidates incorrectly identified B as meiosis spotting the formation of gametes at this stage but failing to deduce that if gametes were formed from a haploid organism they must have been formed by mitosis to maintain chromosome number. 15
16 Question 2(b)(i) Most candidates correctly identified both G phases and the S phase as part of interphase. A few candidates included M and/or C in their answer as shown here. 16
17 Question 2(b)(ii) This question tested candidates knowledge and understanding of the checkpoint immediately following S phase of interphase. The new specification includes the concept of checkpoints in the cell cycle and, in general, candidates answered this question well. As DNA replication occurs during S phase candidates gained the mark for demonstrating an understanding that this checkpoint was for the correct replication of DNA. There were a variety of different possible answers with reference to the ideas of mutations, DNA damage and incorrect duplication. Some candidates included irrelevant information such as checking for processes that would occur in the G phases. It is worth noting that ‘genetic information’ is too vague a term at this level. 17
18 Question 2(c)(i) Most candidates correctly identified Q as the correct cell. The most frequent incorrect answer was R with candidates that selected this cell not spotting that it spent no time in mitosis and was therefore not dividing. 18
19 Question 2(c)(ii) Candidates generally answered this question well. There were a variety of ideas to explain why the S phase may take longer. Cell P having more DNA, as shown here, was the most common correct answer, but other candidates gave correct suggestions including longer chromosomes and having more mutations discovered at the checkpoint. A link to enzyme action could be made here when teaching using the second mark point referring to organisms at lower temperatures. A few candidates gave answers about P being ‘more complex’ but these were not creditworthy. 19
20 Question 2(c)(iii) There was a wide range of possible answers to this question. Candidates could have referred to the table in their answer to indicate that cell R spends all of its time in G1/G0. Other alternatives included stating that the cell could not replicate, was dormant or that the cell was damaged in some way. This answer includes reference to differentiation or specialisation with some candidates extending their answers to suggest the name of a possible specialised cell such as an erythrocyte. Many candidates scored at least one mark on this question. 20
21 Question 2(d)(i) Candidates who calculated the differences incorrectly did not score on this question as shown here. 21
22 Question 2(d)(i) Some candidates failed to state the numerical differences between the two key stages (prophase and telophase) as shown here. The instruction was to identify the pieces of evidence and therefore the table should have been quoted. Either a calculated difference, correctly identifying which had more or fewer, or the correctly stated relative numbers of cells in both phases gained credit. Some candidates only referred to prophase or telophase but the question asked for pieces (plural) of evidence so both should have been given. 22
23 Question 2(d)(ii) This question discriminated between those candidates that were familiar with the t-test and its application and those that were not. A significant number of pupils left this question blank and a few stated that use of the t-test was restricted to analysing biodiversity; perhaps the context in which it had been taught. 23
24 Question 2(e)(i) Many candidates answered this question correctly and had clearly been prepared for this mathematical requirement of the AS specification. Given the information in the table, candidates could use this framework to check their own workings against those of the completed rows and should be encouraged to do so. Errors were only penalised on the first occasion. This candidate has an incorrect chi-squared value. Their first error was to round the calculated value for metaphase incorrectly. Their second error was to give the square of -23 as a negative number. However, they have added their calculated values correctly, and have already been penalised for rounding incorrectly, so can gain one mark for their calculation of chi-squared. It is worth reminding candidates that all the values in a column of a table should be rounded to the same number of decimal places. 24
25 Question 2(e)(iii) Candidates’ answers were marked using their calculated chi-squared value and degrees of freedom from questions 2(e)(i) and 2(e)(ii). Therefore candidates stating incorrect values in previous questions were not penalised at this stage. There were a number of different possible answers to this question as reflected in the mark scheme. This candidate is familiar with the concept of using the 0.05 critical value and also correctly states that the null hypothesis can be rejected. The answer scores the maximum 2 marks and would also gain a mark for stating the difference is significant were an extra mark available. Candidates who did not perform well here failed to select the correct value from the table, or were not able to explain what their calculated chi-squared value meant. 25
26 Question 3(a)(ii) In general this question was answered well. Candidates should spot that the question is worth two marks and that therefore glucose needs to be qualified with either alpha or beta (beta in this case). This candidate has written B glucose, not β glucose. Candidates should be instructed to ensure that their β has a long ‘tail’ so that it cannot be confused with B (potential confusion with protein structure). This is also worth noting for the full linear course with the confusion between β cells in the islets of Langerhans, and B cells in the immune system. 26
27 Question 3(a)(iii) This question proved to be a good discriminator with many candidates able to score two marks out of four by describing the formation of polysaccharides as condensation reactions with the production of water. Fewer candidates were able to develop their answer further by applying their knowledge of cellulose to the formation of chitin despite having identified beta glucose in the previous question. In this example the candidate has identified the similarities to cellulose and predicts the structure of chitin clearly to score the maximum number of marks. A significant minority of candidates confused polysaccharides with protein polymers. 27
28 Question 3(b)(ii) There were a number of different possible ways that candidates could suggest for how the presence of the mites would affect the honeybee. The most common correct answer was to state that the airways would be blocked. Other common answers were the suggestion of disease transmission or that the mites could use oxygen. In this example the candidate has not been specific. They have talked about respiration being less effective without linking this to a lack of oxygen at the cells of the bee. A few candidates talked about the ‘lungs’ of the bee, despite the gas exchange system of insects being on the specification. 28
29 Question 4(a)(i) Most candidates correctly identified Amanita and gave a capital letter A. ‘Eukaryotic’, as in the example, was a common incorrect answer with ‘citrina’ also selected. It is useful for candidates to have a mnemonic to help remember Kingdom, Phylum and so on, and to be reminded of how to identify the genus from the Latin name. 29
30 Question 4(a)(ii) A large number of candidates were not able to state that fungi have extracellular enzymes for digestion, or to deduce from the diagram that the starch had been digested in the region where the fungal hyphae were not present. In this example the candidate refers to ‘it’ but in this case ‘it’ could refer to either the fungi or the enzyme so should not be used. It is worth reminding candidates to avoid the use of the word ‘it’ at the beginning of their answer where there is more than one possible interpretation. 30
31 Question 4(b)(i) Questions 4(b)(i) to (vi) tested how well candidates were able to analyse data from a practical and suggest modifications to procedure. Many candidates gave answers to this question, as shown in the example, that suggested that the pH varied during the experiment but were not able to link this to the production of fatty acids following the action of lipase on lipids. There were a variety of phrases accepted including pH being the dependent variable, or being measured, or indicating the end point. Most candidates gained the mark for this question. 31
32 Question 4(b)(ii) There were 5 different correct answers to this question. Candidates that failed to gain the mark often did so because they did not use correct scientific terminology or, as in this example, did not give enough detail in their answer. Time is one of the controlled variables, but the candidate needed to state that it was the time between samples that was controlled. ‘Amount’ is often seen in answers, but needs to be replaced with volume or concentration in order to get the mark. Candidates lost marks for failing to give the term ‘solution’ after lipase, enzyme or alkaline. In this example answer, ‘30 seconds’ has been stated but this is how the variable was controlled instead of the variable itself. For the same reason 0.5% was also not acceptable – the concentration of lipase solution was needed for the answer. 32
33 Question 4(b)(iii) Candidates that did not gain this mark often gave imprecise terminology again, as in this example. A surprisingly high number of candidates gave temperature as an answer even though the second bullet point on the experimental procedure clearly states the use of a water bath maintained at each temperature. 33
34 Question 4(b)(iv) Many candidates scored the mark on this question by stating that the use of a white tile would make the colour easier to observe. This is a technique used in many practicals where the colour change is observed on a white background of either a tile or in a test tube held against a white lab coat. 34
35 Question 4(b)(v) Few candidates scored this mark. The data indicates that the optimum temperature lies in the range of 30 to 35 °C. Most candidates gave a single figure for their answer, as indicated in the example. When drawing a graph of enzyme activity with students it is useful to sketch three different peaks on the board showing that without carrying out the practical at the intermediate temperatures the actual optimum cannot be known. Units needed to be stated on at least one of the temperatures in the range, so an answer of ‘30 to 35’ would not have gained credit. 35
36 Question 4(b)(vi) This question was challenging for many candidates. Very few scored more than 2 marks. Candidates who talked about repeats did not gain marks here as the key word in the question was ‘accurate’. This candidate has obtained full marks with clear instructions of how to modify procedure. Units were again needed when giving the temperature range. Some candidates talked about the use of a colorimeter but did not always explain that this would lead to a less subjective result. A few candidates mentioned the use of a pH meter or probe but usually failed to pick up the second mark by stating that this would give a numerical value which would be more accurate. 36
37 Question 4(c) This was the first of two Level of Response (LoR) questions on this paper. These questions are marked holistically, looking at the whole answer. Most candidates scored level 2 on this question. Only those candidates that talked clearly about both low and high temperatures and their different effects on enzyme action scored the maximum mark as shown in this example. Descriptions of the lock and key and induced fit hypotheses were generally good. Weaker candidates incorrectly stated that denaturation occurred at low temperatures and failed to talk about the induced fit mechanism in full detail. Some candidates gave very detailed answers but a common omission was detail of the effect of low temperature on enzyme action for example a discussion of kinetic energy and collisions between active site and substrate. Candidates generally used correct terminology for example active site, enzyme substrate complex and products.
38 Question 5(a)(ii) Most candidates scored this mark for stating that fish have a single circulation whereas mammals have a double circulation. Candidates that failed to gain a mark here often gave vague answers without the key terms as in this example. This candidate is also using ‘it’ in an answer where they could be describing either the fish or the mammal. It is worth noting that candidates are asked to compare both circulations in the question and should therefore describe both, not just one. 38
39 Question 5(b) This question produced a wide spread of marks and many candidates found it challenging. Candidates who scored full marks, as in the example, described both circulations and were able to compare the efficiency of both. Many candidates realised the oxygenated and deoxygenated blood mixed in the frog but not the mammal with better candidates discussing the septum. Not many candidates referred to the spiral valve despite it being shown on the insert. A surprisingly low number of candidates discussed the number of chambers in each heart even though this was clear from the insert. In general the description of the circulatory system was better than the discussion of the effectiveness. Candidates tended to say that the frog circulation would be less efficient than the mammal, although a discussion of the lower metabolic rate and therefore decreased oxygen requirement of the frog appeared in the best answers. This second LoR question tended to be more challenging than the first. 39
40 Question 6(a)(i) Many candidates found this question challenging. In this example, the candidate has not made it clear that these bacteria were on the original plate and also in the third diagram, or also present when the plate was flooded with penicillin. They describe the bacteria being placed into the penicillin but this is referring to the second plate and is therefore not creditworthy. 40
41 Question 6(a)(i) In this answer the candidate is clear that the bacteria continue to grow after the plate is flooded and therefore gains the mark. 41
42 Question 6(a)(ii) Many candidates answered this question correctly with the response ‘natural selection’. A significant minority incorrectly stated that mitosis occurred in bacteria. Other answers that did not gain credit included evolution, mutation and binary fission. These are not enough for a mark as mutation and binary fission would not necessarily increase the proportion of penicillin-resistant bacteria; natural selection needs to be stated as it is the process by which evolution occurs. 42
43 Question 6(b)(i) Candidates found the mathematical requirements of this question challenging. Although many were able to select the correct figures to use, candidates often were unable to calculate the percentage increase correctly, and were also often unable to give an answer to three significant figures. This candidate demonstrates the importance of showing working in an answer as they have gained one mark for correct working even though their final answer is incorrect. 43
44 Question 6(b)(ii) Candidates found this question more straightforward and were able to calculate the correct answer 52%. The majority of candidates gained two marks for this question by correctly stating that the figure for 2012 was an increase compared to 1993. 44
45 Question 6(b)(iii) Most candidates scored one mark on this question for stating that there had been a decrease in deaths in the time period. Candidates who talked about a large decrease did not always get the mark as they needed to specify that MRSA showed the large decrease, not S. aureus in general. This candidate has been awarded the mark for correctly processing data to give a 73% decrease and there were several different ways to process the data to gain this mark. Candidates who merely quoted data from the table did not gain a mark. Some manipulation of data needed to be carried out such as percentage decrease or actual decrease. This candidate would not have gained the mark for cross-infection control as they needed to state more detail for this mark, such as the use of pre operation screening for MRSA. 45
46 Summary In conclusion, the aim of this presentation was to show which parts of the H020/02 Depth in Biology exam paper were done well and which were done badly. In general candidates demonstrated good factual recall and tended to find questions requiring the application of knowledge more challenging. The greater mathematical requirements of the new specification proved more challenging for some candidates and the calculation of percentage change continues to be poorly answered in many cases. The new LoR questions gave candidates opportunities to discuss two areas of biology in great depth and the question on enzymes, 4c, showed good biological knowledge from many candidates. It is important to stress to candidates the importance of reading a question carefully and, if faced with an unfamiliar context, to think about how their own studies can be related to this new situation, before starting to write their answer.
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