AQA BIOLOGY PAPER 3 JUNE 2020 QUESTION PAPER

Distribution of this document is illegal AQA Biology Paper 3 2020 S - The Marketplace for Revision Notes & Study Guides Distribution of this document is illegal Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. IB/M/J un20/ /3 A-level BIOLOGY Paper 3 Monday 15 June 2020 Morning Time allowed: 2 hours Materials For this paper you must have:  a ruler with millimetre measurements  a scientific calculator. Instructions  Use black ink or black ball-point pen.  Fill in the boxes at the top of this page.  Answer all questions in Section A.  Answer one question from Section B.  You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages.  If you need extra space for your answer(s), use the lined pages at the end of this book. Write the question number against your answer(s).  Show all your working.  Do all rough work in this book. Cross through any work you do not want to be marked. Information  The marks for the questions are shown in brackets.  The maximum mark for this paper is 78. For Examiner’s Use Question Mark 1 2 3 4 5 6 7 TOTAL 1 Section A Answer all questions in this section. You are advised to spend no more than 1 hour and 15 minutes on this section. Do not write outside the box Guppies are small fish. Female guppies are dull in colour. Male guppies can be bright or dull in colour. Scientists investigated the effect of female brain size on choosing a mate. They used laboratory-bred female guppies with large brains and with small brains. They set up a fish tank as shown in Figure 1. Figure 1 They observed each female for 10 minutes and recorded which male they were attracted towards. They repeated this with 45 large-brained females and 45 small-brained females. . Suggest three possible limitations of this investigation. [3 marks] 1 2 3 0 1 0 1 S - The Marketplace for Revision Notes & Study Guides 3 *03* Downloaded by: jessicaonyebuchi | Distribution of this document is illegal IB/M/Jun20/7402/3 2 3 Guppies with large brains are better at identifying predators. The scientists found that only female guppies with large brains were attracted to male guppies bright in colour. Do not write outside the box . Suggest and explain the advantage of this behaviour to the population of guppies. [3 marks] . Describe how the behaviour of female guppies could result in sympatric speciation. [3 marks] Turn over ► 0 1 0 1 9 S - The Marketplace for Revision Notes & Study Guides 4 1 In northern India, there is a conflict of interests between farmers of livestock (eg cows) and people trying to conserve ibex (a type of wild goat). When livestock are given extra food, their populations can grow too large and compete with ibex. Do not write outside the box . Name the type of competition between livestock and ibex. [1 mark] Livestock will outcompete ibex if they:  are in the same habitat  eat a similar diet. Scientists investigated this conflict of interests. Table 1 summarises some of the scientists’ findings. Table 1 Type of livestock Difference between livestock food and ibex food* Difference between livestock habitat and ibex habitat* Cow 1.0 1.5 Horse 0.5 0.0 Yak 0.0 2.0 * A score of 0.0 indicates that the food or habitat is the same. 0 2 0 2 . 2 There must be a balance between the need for conservation of the ibex and the need for farmers to keep livestock. Using all the information, suggest and explain three actions that the farmers could take to achieve this balance. Do not write outside the box [3 marks] 1 2 3 Turn over for the next question Turn over ► 0 2 4 1 2 3 In Europe, viruses have infected a large number of frogs of different species. The viruses are closely related and all belong to the Ranavirus group. Previously, the viruses infected only one species of frog. Do not write outside the box . Suggest and explain how the viruses became able to infect other species of frog. [2 marks] . Name two techniques the scientists may have used when analysing viral DNA to determine that the viruses were closely related. [1 mark] 1 2 . Determining the genome of the viruses could allow scientists to develop a vaccine. Explain how. [2 marks] 0 3 0 3 0 3 0 3 . 4 Describe how the B lymphocytes of a frog would respond to vaccination against Ranavirus. You can assume that the B lymphocytes of a frog respond in the same way as B lymphocytes of a human. Do not write outside the box Do not include details of the cellular response in your answer. [3 marks] Turn over for the next question Turn over ► 0 3 8 1 Table 2 shows information about two types of medicine. Table 2 Name of medicine Mass of medicine in one tablet / mg Maximum dose of medicine an adult is allowed Mass of sodium in one tablet / g Aspirin 300 0.6 g every 4 hours 0.15 Paracetamol 500 1.0 g every 6 hours 0.43 . A journalist studied the data in Table 2. She made the following suggestion. ‘If an adult takes the maximum number of tablets allowed for either of the medicines, then the person would have more than the RDA of sodium.’ The RDA (recommended daily allowance) of sodium for an adult human is 2.4 g per day. Is the journalist’s statement true for both of the medicines in Table 2? Use suitable calculations to support your answer. Do not write outside the box Show your working. [2 marks] 0 4 0 4 Doctors investigated the link between high sodium concentrations in medicines and hypertension (high blood pressure). They analysed medical records of patients. 1 of these patients had taken medicines containing high sodium concentrations. Each of these patients was paired with a patient from a control group. Do not write outside the box 0 4 . 2 Give two factors that should have been the same for each pair of patients and one factor that should have been different. [2 marks] Same factor 1 Same factor 2 Different factor 0 4 . 3 Doctors found:  4.73% of the patients who had taken medicines containing high sodium concentrations suffered from hypertension  there were 7.18 times fewer control patients with hypertension. Calculate how many of the control patients had hypertension. Show your working. [2 marks] Answer patients Question 4 continues on the next page Turn over ► . 4 A high concentration of sodium in the blood can affect blood volume and cause hypertension. Use your knowledge of water potential to suggest how high sodium concentrations in the medicines taken could affect blood volume. Do not write outside the box [3 marks] 0 4 9 1 2 . In the UK in 2016, there were 525 048 deaths. Cancer caused 30.4% of all deaths. Throat cancer caused 5% of all deaths from cancer. Calculate the mean number of people who died of throat cancer per month in 2016. Do not write outside the box Show your working. [2 marks] Answer people per month Increased methylation of the promoter region of a tumour suppressor gene causes one type of human throat cancer. In this type of throat cancer, cancer cells are able to pass on the increased methylation to daughter cells. The methylation is caused by an enzyme called DNMT. Scientists have found that a chemical in green tea, called EGCG, is a competitive inhibitor of DNMT. EGCG enables daughter cells to produce messenger RNA (mRNA) from the tumour suppressor gene. . Suggest how EGCG allows the production of mRNA in daughter cells. [3 marks] Question 5 continues on the next page Turn over ► 0 5 0 5 3 The scientists investigated the effect of different amounts of EGCG on the growth rate of the throat cancer cells grown in vitro. Their results are shown in Figure 2. Figure 2 . A reporter who reviewed all of this work concluded that drinking green tea could be a cure for cancer. Do not write outside the box Suggest three reasons why his conclusion might not be valid. [3 marks] 1 2 3 0 5 8 Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Do not write outside the box Turn over ► . 1 Describe the advantage of the Bohr effect during intense exercise. [2 marks] Do not write outside the box A cyclist completed a fitness test on an exercise bike. The intensity of the exercise was increased every 10 seconds. The test finished when he was unable to cycle any further. The partial pressure of oxygen (pO2) and of carbon dioxide (pCO2) in air breathed out was measured. Figure 3 shows the results of the cyclist’s fitness test. Figure 3 Ventilatory threshold (VT) is a measure of the point when anaerobic respiration increases because aerobic respiration alone can no longer maintain muscle contraction. 0 6 2 3 . VT can be identified as the first point when there is an increase in pO2 breathed out, without an equivalent increase in pCO2 breathed out. Use Figure 3 to determine the time after the exercise started when the cyclist reached VT. Calculate the ratio of pO2 to pCO2 in breathed-out air at this time. Do not write outside the box Show your working. [2 marks] Time when the cyclist reached VT = min Ratio of pO2 to pCO2 at VT = :1 . An increase in the intensity of exercise produces an increase in the volume of carbon dioxide produced. However, Figure 3 shows that the pCO2 in air breathed out did not show a large increase during the exercise. Suggest one physiological change that would cause this result. Explain how the physiological change would allow for the removal of the increase in the volume of carbon dioxide produced. [2 marks] Physiological change Explanation Question 6 continues on the next page 0 6 0 6 Turn over ► 4 When muscle fibres have very low concentrations of ATP, they may get ATP in the following ways.  AMPK (an enzyme) oxidises fatty acids.  Phosphocreatine donates phosphate to ADP in anaerobic conditions. Figure 4 shows how these chemicals work. Figure 4 . At more than 80% of maximum muscle effort, ATP can only be made for a limited time. Use Figure 4 to suggest one reason why. Do not write outside the box Tick (