GCSE Biology. BL3HP Report on the Examination June Version: 1.0

Transcription

1 GCSE Biology BL3HP Report on the Examination 4401 June 2014 Version: 1.0

2 Further copies of this Report are available from aqa.org.uk Copyright 2014 AQA and its licensors. All rights reserved. AQA retains the copyright on all its publications. However, registered schools/colleges for AQA are permitted to copy material from this booklet for their own internal use, with the following important exception: AQA cannot give permission to schools/colleges to photocopy any material that is acknowledged to a third party even for internal use within the centre.

3 Question 1 (Standard Demand) (a) (i) The vast majority of students gained full credit in this question. Where students failed to gain the full two marks, it was often due to incorrect rounding of the answer. (a) (ii) Most students gained two or more marks on this question. Most students correctly identified the increase and decrease in the pattern. Students that went on to give reasons for the increase and decrease often mixed the reasons up, with a significant number suggesting the decrease was due to the introduction of quotas and the increase was also due to the introduction of quotas. The most able students could correctly link the decrease with overfishing and the subsequent increase to the introduction of quotas. A significant minority of students described the pattern for the sustainable fish instead of fish from all sources. (a) (iii) A number of students failed to gain credit on this question, often due to describing why it was important to fish sustainably rather than answering the question that was asked. Thus answers relating to fishermen choosing to fish sustainably was insufficient for this question. Those students who did gain credit expressed the increase in public awareness or impact of legislation in a variety of ways. (c) There was a good spread of marks in this question and many students gained credit. Students often attempted to describe net regulation and confused net and mesh size, and therefore did not gain the mark. Over half of all students gained three or four marks on this question. Students generally understood the idea of restricted movement leading to a saving of energy, which could then be used for growth. Some students mentioned that food could be controlled but not many expressed the idea that they could be given more or better quality food. A popular misconception was that fish are warm blooded and a significant number of students described temperature regulation, and how fish farming made temperature regulation easier for fish as they are close together. There was also a number of references to the fish being protected from predators, without taking it a stage further to gain the less movement mark e.g. as they don t need to escape. Question 2 (Standard Demand) Most students managed to score marks in Level 2 or 3. Most students could suggest some reasons for deforestation although some penalised themselves by concentrating solely on uses for the reclaimed land rather than also considering uses for the timber. More able students could list three or four reasons for deforestation and linked them to the changes in carbon dioxide and methane levels. The consequences of deforestation were well known with some excellent answers given. However there are still too many students who seem to think that trees are like balloons full of carbon dioxide which is released when a tree is felled. More able students were well versed in the recycling of carbon dioxide from trees, including: photosynthesis; sequestration of carbon locking carbon in trees and release of carbon dioxide by microbes respiring during decomposition. 3of 7

4 A reasonable number thought through the whole procedure of deforestation, mentioning carbon dioxide production from transport and logging machinery. A number of students used the picture and question statements to map out a brief plan or bullet points to help guide them. Question 3 (Standard Demand) (a) Most students gained 2 marks for correctly identifying the partially permeable membrane, and approximately a quarter of all students went on to gain the third mark for correctly identifying the direction of travel of water. If students stated a movement of water from high to low concentration, this was only awarded if the student made it clear that they are referring to the concentration of water, i.e. from dilute to concentrated solutions. A significant number of students simply referred to movement of water from a high to a low concentration, which was not creditworthy. Movement along or up the gradient were seen quite often with a correct description for mark point 3, and unfortunately, this cancelled the mark for these students. Gases and mineral ions moving by osmosis were seen occasionally. A small number of students gained one mark for correctly identifying that osmosis is a passive process. Just over half of all students gained two or three marks in this question, with most students correctly identifying the large surface area of the structures. However, there was confusion between root, root hair and root hair cell. A significant number of students started their explanations with it or they and were not awarded the first mark point. Some students referred to fibres or the root itself for no credit, and similarly long root hairs was insufficient. Students often failed to gain the third mark as they simply restated the stem by stating therefore more water can be absorbed, and did not clearly identify that more osmosis would occur. Erroneous responses about movement of mineral ions or water moving by active transport were seen. Question 4 (Standard and High Demand) (a) (i) Approximately two thirds of students gained credit in this question. Some students are still confusing antigen and antibody which led to them losing marks. A significant minority answered in vague terms such as destruction of the disease or illness rather than pathogens or named microorganisms. Many synonyms for destroy were seen and were creditworthy, such as kill, digest, engulf and ingest. (a) (ii) The vast majority of students correctly identified the feature of platelets. (c) The vast majority of students gained one or two marks in this question. Incorrect answers often referred to urea being made in the kidney and removed from the blood by the bladder. Over three quarters of all students gained one or two marks on this question. A significant number of students frequently gave 3 or 4 creditworthy responses in their answer. There were some vague references to pressure which did not gain credit as they did not clearly relate to the valve having to withstand the pressure. A significant minority of students made reference to the valve having to pump blood which was clearly incorrect. 4of 7

5 Question 5 (High Demand) (a) (i) The vast majority of students gained credit in this question. (a) (ii) Many students did well in this question and understood aspects of gaseous exchange. For those who took this approach a minority lost the mark for having CO 2 or O 2 moving in the 'wrong direction' as they hadn't specified that this occurred at night. Those who took the water approach did less well as the 'control' aspect was missing from their response. (i) Only a third of all students gained credit for calculating the number of stomata per mm 2, and around half did not gain any marks. There was evidence that many students are not good at multiplying decimals and put the decimal point in the incorrect place, giving 2 or 20 as the number of stomata. (ii) Approximately two thirds of all students could correctly identify a disadvantage of having a large number of stomata. Where students did not gain credit, it was often for giving an answer that was not comparative, e.g. plant will lose water as opposed to the plant will lose more water. (c) (i) Just over half of all students correctly worked out the amount of water lost. (c) (ii) Approximately two thirds of students gained two or three marks on this question. Those students who recognised the role of stomata in water loss could gain at least 1 mark, usually for stating that the stomata were blocked by the grease. Many did not point out that the majority of the stomata are on the lower surface of the leaf, merely stating that there were many stomata on the lower surface and so failed to gain that mark. Those students who failed to mention stomata and rephrased the given data, gained no credit. Question 6 (High Demand) (a) (i) Approximately three quarters of students gained credit in this question. (a) (ii) About two thirds of all students gained three or more marks in this question. Most students were correctly able to describe the shape of both lines on the graph. Many students used data to enhance their descriptions giving more depth than was required in the mark scheme. Some students had not read the question correctly and described the body and skin temperatures before 9.15 or after in addition to the section between 9.15 and as the question asked. Marking point 2 was very rarely awarded as most students did not refer to respiration or muscle contractions as the reason for body temperature increasing. Those that did often did not include the idea of more respiration or muscle contraction and therefore were not awarded this mark. Few marks were awarded for the marking point of releasing energy. Often students did not mention this but when they did many referred to energy being made or produced as opposed to released and so could not be awarded this mark. 5of 7

6 The majority of students referred to sweating as the reason that skin temperature decreases during exercise and many of these students then explained how this happens by referring to cooling by evaporation in their answers. Many students spent time explaining how blood vessels could alter the blood flow to the skin as a method of heat loss, which was not relevant. Others included information about hairs lying flat on the skin or about the role of the thermoregulatory centre, both of which were ignored by examiners. Some students who did not realise the importance of the command words used in the question wrote lengthy descriptions of the graph instead of explaining the shape of the graph as well. (a) (iii) Students found this question difficult, and over half did not gain any marks. Many students thought that the body needed to conserve heat and so described vasoconstriction. Many of those who chose vasodilation lost a mark by referring to blood vessels moving about in the skin. Students were generally scoring two marks for realising that glucagon was involved and that this caused the conversion of glycogen into glucose. Few students stated that the pancreas detects changes in blood glucose levels, but they did say that it was the pancreas that was involved or was producing the glucagon. There were a significant number of spelling errors, students maybe knowing the story but not gaining marks because the spellings were ambiguous, such as glygogon or glucogen. A number of students stated that glucagon was an enzyme. Question 7 (High Demand) (a) (i) Examiners found that students struggled to apply their knowledge to the context of the biogas generator given in this question. Most answers stated that not enough time had elapsed for enough biogas to be generated, with no reference to aerobic or anaerobic respiration and the gases produced. Very few students recognised that oxygen would be present and available to the microbes at the start of the investigation. (a) (ii) Approximately a quarter of students gained credit on this question. Where students didn t it was often because they did not refer to the potato peelings having the most carbohydrate. A number of other responses suggested that the other foods, having been cooked, would somehow prevent them giving as much biogas. (i) This question was answered well. The correct positioning of the decimal point was problematic for a number of students who were permitted '1 mark for 22.1' alternative. Some students are still losing out on possible credit by not showing working. (ii) This question was generally answered well with most students comparing the volume of biogas and percentage of methane for sheep and cow to gain two marks. A few students did the calculation, and were invariably correct. Some students gained only one mark for comparing either biogas volume or percentage methane but not both. A number chose to compare other animals in the table. 6of 7

7 Mark Ranges and Award of Grades Grade boundaries and cumulative percentage grades are available on the Results Statistics page of the AQA Website. Converting Marks into UMS marks Convert raw marks into Uniform Mark Scale (UMS) marks by using the link below. UMS conversion calculator 7of 7