2024_AQA: A-level BIOLOGY Paper 2 (Merged Question paper and marking scheme) Friday 14 June 2024

2024_AQA: A-level BIOLOGY Paper 2 (Merged Question paper and marking scheme) Friday 14 June 2024 Please write clearly in block capitals. Centre number Surname Forename(s) Candidate signatu re Candidate number I declare this is my own work. A-level BIOLOGY Paper 2 Friday 14 June 2024 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. Morning  You must answer the questions in the spaces provided. Do not write outside the box around each page or on blank pages. Time allowed: 2 hours For Examiner’s Use Question Mark 1 2 3 4 5 6  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 91. 7 8 9 10 TOTAL A-level Biology Paper 2: Key Areas to Revise This paper focuses on more advanced topics and builds on your understanding of biological principles. Key areas to revise include: 1. Cell Recognition and the Immune System: Build on your understanding of the immune system, including the role of T-cells, B-cells, and antibodies in recognizing and responding to pathogens. Study the primary and secondary immune responses, the role of antigen-presenting cells, and the use of vaccines and monoclonal antibodies. 2. Bioenergetics: Deepen your understanding of photosynthesis and cellular respiration. Be familiar with the light-dependent and light-independent reactions of photosynthesis, and know how they differ from each other. For cellular respiration, understand glycolysis, the Krebs cycle, oxidative phosphorylation, and anaerobic respiration. 3. Infectious Diseases: Study the characteristics of pathogens (bacteria, viruses, fungi, etc.) and how they cause diseases in humans and other organisms. Understand the transmission, prevention, and treatment of infectious diseases. Be familiar with the role of antibiotics, antiviral drugs, and emerging diseases. 4. Inheritance, Variation, and Evolution: Review the principles of genetic inheritance, including Mendelian genetics, codominance, and sex-linked inheritance. Understand genetic variation in populations and how natural selection, genetic drift, and speciation lead to evolutionary change. 5. The Nervous System: Focus on the structure and function of neurons, synapses, and the nervous system. Understand how nerve impulses are transmitted, including action potentials, synaptic transmission, and the role of neurotransmitters. Be familiar with the central and peripheral nervous systems, including reflex actions. 6. Plant and Animal Responses: Study the mechanisms of coordination in plants and animals. For plants, focus on tropisms and the role of plant hormones like auxins. For animals, focus on the nervous and endocrine systems in regulating physiological processes such as the fight-or-flight response. 7. Practical Skills and Data Analysis: Expect questions related to interpreting experimental data, drawing conclusions, and understanding laboratory techniques. Be sure to revise methods used in biological investigations, such as enzyme activity experiments, the use of microscopes, and measuring rates of biological processes. By reviewing these topics thoroughly, you'll be well-equipped for the diverse range of questions you may encounter on A-level Biology Paper 2. IB/M/Jun24/G4006/E7 7402/2 2 Do not write outside the box Answer all questions in the spaces provided. IB/M/Jun24/7402/2 0 1 Figure 1 shows a drawing of a neuromuscular junction. Figure 1 0 1 . 1 Name the parts labelled A to D. [2 marks] A B C D 3 Do not write outside the box IB/M/Jun24/7402/2 0 1 . 2 Following the release of acetylcholine into a neuromuscular junction, a muscle contraction occurs. Describe the sequence of events, following the release of acetylcholine, that leads to stimulation of this contraction. Do not include in your answer the events following the release of calcium ions in the myofibril. [4 marks] 0 1 . 3 Inhibitory synapses cause hyperpolarisation in postsynaptic neurones. Explain how this inhibits synaptic transmission. [2 marks] Turn over ► 8 4 Do not write outside the box IB/M/Jun24/7402/2 0 2 . 1 Figure 2 shows part of a relaxed myofibril. Figure 2 The myofibril represented in Figure 2 has 34 sarcomeres. The length of every sarcomere is 2 µm After contraction of this myofibril, the length of each sarcomere changed by 20%. Use the information provided to calculate the length of the myofibril after contraction. Give your answer in mm and in standard form. Show your working. [2 marks] Answer mm 5 Do not write outside the IB/M/Jun24/7402/2 2 . Which statement correctly describes the changes in length in a sarcomere when a myofibril contracts? box Tick () one box. [1 mark] H-zone decreases, I-band increases, A-band decreases H-zone increases, I-band decreases, A-band decreases H-zone decreases, I-band decreases, A-band no change H-zone increases, I-band increases, A-band no change 0 2 . 3 Fast muscle fibres have a higher concentration of glycogen than slow muscle fibres. Explain how the difference in glycogen concentration is related to the different properties of these muscle fibres. [4 marks] Turn over ► 7 2 0 6 Do not write outside the box IB/M/Jun24/7402/2 0 3 . 1 A biologist investigated photosynthesis. They:  measured the percentage of light absorbed by a plant when it was exposed to different wavelengths  measured the rate of photosynthesis at each wavelength of light. Figure 3 shows the results they obtained. Figure 3 Using Figure 3, what can you conclude about the relationship between: [2 marks] the percentage of light absorbed and the rate of photosynthesis the colour of light and the rate of photosynthesis 7 Do not write outside the box IB/M/Jun24/7402/2 0 3 . 2 Give three environmental factors that should be controlled when measuring the rate of photosynthesis in this investigation. Do not include features of the plant in your answer. [2 marks] 1 2 3 0 3 . 3 Describe how the products of the light-dependent reaction are used in the light-independent reaction to produce triose phosphate. Do not include the role of ribulose bisphosphate (RuBP) in your answer. [3 marks] Turn over ► 7 8 Do not write outside the box IB/M/Jun24/7402/2 0 4 . 1 In fruit flies, a gene for body colour has a dominant allele for grey body, G, and a recessive allele for black body, g. Explain how you would determine if the genotype of a grey fly is homozygous or heterozygous for body colour. [2 marks] 0 4 . 2 In fruit flies, males are XY and females are XX. A cross between a grey-bodied male fly and a black-bodied female fly produced some black-bodied females. Explain how this shows that the gene for body colour is not sex-linked. [1 mark] 9 Do not write outside the box IB/M/Jun24/7402/2 Genotypes of offspring Phenotypes of offspring Ratio of offspring 8 0 4 . 3 A population of fruit flies contained 19% grey-bodied flies. Use the Hardy–Weinberg equation to calculate the percentage of flies heterozygous for gene G. Show your working. [2 marks] Answer % 0 4 . 4 In fruit flies, a gene for wing shape has a dominant allele for curly wings, R, and a recessive allele for normal wings, r. The alleles for this gene are on a different pair of chromosomes from the gene for body colour. Fruit flies that are homozygous dominant for curly wings do not survive beyond the embryo stage. A curly-winged fly, homozygous for grey body colour was crossed with a curly-winged, black-bodied fly. Complete the genetic diagram to show all the possible genotypes and the ratio of phenotypes expected to develop into adults from this cross. [3 marks] Phenotypes of parents Curly-winged, grey-bodied, × Curly-winged, black-bodied Turn over ► Genotypes of parents × 10 Do not write outside the box IB/M/Jun24/7402/2 0 5 . 1 A weed is a plant growing where it is not wanted. Fat hen is a weed which grows in some crop fields. Describe how you could estimate the number of fat hen plants in a field. [5 marks] 11 Do not write outside the box IB/M/Jun24/7402/2 0 5 . 2 In potato plant fields, fat hen plants can grow up to a height of 2 m and absorb large quantities of nutrients from the soil. Fat hen has a negative effect on the growth of potato plants. Use the information provided to explain why. In your answer, name the type of competition occurring between fat hen plants and potato plants. [3 marks] Question 5 continues on the next page Turn over ► 12 Do not write outside the IB/M/Jun24/7402/2 3 During a growing season, it was estimated that a total number of 550 fat hen plants grew on the fields of a farm. Calculate the maximum mass, in kg, of viable fat hen seeds on this farm after a growing season. Show your working. Assume that all the seeds produced during the growing season remain on the farm. [2 marks] Answer kg 10 . Table 1 gives some features of fat hen seeds. Table 1 box Feature of seed Mean mass / mg 0.77 Maximum number produced per fat hen plant during a growing season 20 000 Percentage viable (able to develop) after a growing season 79 5 0 13 Do not write outside the IB/M/Jun24/7402/2 Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED box Turn over ► 14 Do not write outside the IB/M/Jun24/7402/2 box 0 6 . 1 Describe the myogenic stimulation of the heart and how the regular contraction of the atria and ventricles is coordinated. Do not include the autonomic nervous system in your answer. [5 marks] 15 Do not write outside the IB/M/Jun24/7402/2 2 . Atrial fibrillation (AF) is a condition that causes an irregular heart rate. Scientists used a statistical test to investigate the association between different factors and the risk of developing AF. Table 2 shows some of the scientists’ results, including the probability (P) values obtained using the statistical test. Table 2 box Factor Probability (P) value for association between factor and risk of AF Age 0.004 High blood pressure 0.001 High LDL (Low-density lipoprotein) concentration 0.222 Hyperthyroidism 0.018 What can you conclude from Table 2? [3 marks] Turn over ► 8 6 0 16 Do not write outside the IB/M/Jun24/7402/2 box 0 7 . 1 BamH1 and HindIII are both restriction endonucleases. Figure 4 shows the positions where these enzymes cut a linear molecule of DNA. Figure 4 In two experiments, multiple copies of the DNA molecule shown in Figure 4 were all completely cut into fragments using these restriction enzymes. The DNA fragments produced were then separated by electrophoresis. Experiment 1 – DNA cut into fragments using BamH1. Experiment 2 – DNA cut into fragments using BamH1 and HindIII. 17 Do not write outside the box Complete Figure 5 to show the relative positions of the bands following IB/M/Jun24/7402/2 electrophoresis in experiments 1 and 2. [2 marks] Figure 5 0 7 . 2 Suggest how you could determine the size of the different DNA fragments produced in these experiments. [2 marks] Turn over ► 18 Do not write outside the box IB/M/Jun24/7402/2 0 7 . 3 How many DNA fragments would be produced in experiment 2 if the original DNA molecule was a plasmid? [1 mark] 0 7 . 4 Describe how restriction endonuclease and DNA ligase are used to insert a gene into a plasmid. [2 marks] 7 19 Do not write outside the box Turn over for the next question IB/M/Jun24/7402/2 DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Turn over ► 20 Do not write outside the box IB/M/Jun24/7402/2 0 8 Plant cells are surrounded by a rigid cell wall. Cell wall plasticity refers to the ability of a cell wall to stretch permanently. IAA is a growth factor which can activate enzymes that loosen the cell wall. Scientists investigated the effect of IAA concentration on cell wall plasticity and the growth of stem segments. Figure 6 shows some of the scientists’ results. Figure 6 0 8 . 1 Use the information provided to explain the relationship between IAA concentration, cell wall plasticity and mean growth of the stem segments. [2 marks] 21 Do not write outside the box IB/M/Jun24/7402/2 0 8 . 2 Use Figure 6 to calculate the percentage increase in mean growth of the stem segments when the IAA concentration was increased from 10–8 mol dm–3 to 10–5 mol dm–3 Give your answer to 2 significant figures. Show your working. [2 marks] Answer % Question 8 continues on the next page Turn over ► 22 Do not write outside the box Gibberellic acid (GA) is another plant growth factor. A student was asked to design IB/M/Jun24/7402/2 and carry out an investigation into the effect of different concentrations of GA on the growth of stem segments. The student was provided with:  10–1, 10–2, 10–3, 10–4 and 10–5 mol dm–3 concentrations of GA solution  distilled water  6 Petri dishes and access to glassware  60 stem segments of different lengths. 0 8 . 3 A technician produced the different concentrations of GA solution from a stock 10–1 mol dm–3 concentration of GA. Describe how the technician produced the 10–3 mol dm–3 solution. [1 mark] 23 Do not write outside the box IB/M/Jun24/7402/2 0 8 . 4 Describe a suitable procedure the student could follow to investigate the effect of different concentrations of GA on the growth of stem segments. In your answer, you should include the variables that should be controlled in this investigation. [5 marks] Turn over ► 10 24 Do not write outside the box There are no questions printed on this page IB/M/Jun24/7402/2 DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED 25 Do not write outside the box IB/M/Jun24/7402/2 0 9 A person with diabetes is in diabetes remission if their blood glucose concentration is below the diabetes threshold concentration for at least 3 months. This diabetes remission is achieved without taking medication. Scientists investigated whether a weight-loss programme would result in type II diabetes remission. The scientists:  used a computer-generated list to select 380 volunteers from a large number of health centres  selected volunteers aged 25 to 60 years, each with less than 5 years duration of type II diabetes  divided the volunteers in the ratio 1 : 1 between experimental group P and control group Q  placed group P on a weight-loss programme for the 2-year duration of this investigation  recorded loss of mass and percentage of volunteers in each group in type II diabetes remission after 2 years. 0 9 . 1 Give two reasons why a weight-loss programme could be used to treat type II diabetes but not type I diabetes. [2 marks] 1 2 Question 9 continues on the next page Turn over ► 26 Do not write outside the box IB/M/Jun24/7402/2 0 9 . 2 The design of this investigation helps to support the validity of any conclusions obtained. Suggest and explain three features of this investigation that justify this statement. [3 marks] 1 2 3 27 Do not write outside the IB/M/Jun24/7402/2 3 . Table 3 shows some of the scientists’ results. Table 3 Group P Group Q Percentage achieving diabetes remission 42.1 4.7 Percentage achieving weight loss ≥15 kg 15.8 2.1 Percentage with weight loss ≥15 kg achieving diabetes remission 70.0 75.0 Percentage with weight gain achieving diabetes remission 1.9 1.9 Question 9 continues on the next page box Turn over ► 9 0 Use the information provided to calculate the difference in number of volunteers between the two groups who achieved diabetes remission. Show your working. [2 marks] Answer 28 Do not write outside the box IB/M/Jun24/7402/2 0 9 . 4 Use all the information to evaluate whether a weight-loss programme is an effective treatment for type II diabetes. [4 marks] 11 29 Do not write outside the box IB/M/Jun24/7402/2 1 0 Read the following passage. The wall gecko is a medium-sized lizard. In an isolated habitat of southern Italy, the wall gecko shows phenotypic diversity. Scientists investigated whether disruptive selection was leading to sympatric speciation in the wall gecko. Pale geckos live only on walls and are nocturnal (active at night). Dark geckos live mainly on the dark trunks of olive trees and are diurnal (active during the day). These diurnal geckos can change skin colour when occupying different surfaces during the day. Comparison of mitochondrial genes indicated that the diurnal geckos formed a distinct genetic group. This comparison also confirmed that all the geckos in the habitat were of the same species. The scientists used the mark-release-recapture method to estimate the size of the population of geckos in the habitat. 5 10 Use the information in the passage and your own knowledge to answer the following questions. 1 0 . 1 The wall gecko shows phenotypic diversity (lines 1–2). Suggest two factors that have resulted in this phenotypic diversity. [2 marks] 1 2 Question 10 continues on the next page Turn over ► 30 Do not write outside the box IB/M/Jun24/7402/2 1 0 . 2 The ability of diurnal geckos to change skin colour (lines 7–8) is advantageous. Explain why. [2 marks] 1 0 . 3 The scientists concluded that it was probable that disruptive selection was leading to sympatric speciation in the wall gecko. Use the information in the passage to evaluate this conclusion. [5 marks] 31 Do not write outside the box IB/M/Jun24/7402/2 1 0 . 4 Explain how comparison of mitochondrial genes could indicate that the nocturnal geckos formed a distinct genetic group (lines 9–10). In your answer, explain how new techniques enable the comparison of genes to be completed rapidly. [3 marks] Question 10 continues on the next page Turn over ► 32 Do not write outside the box IB/M/Jun24/7402/2 1 0 . 5 Describe and explain two precautions required to ensure that the estimate of the size of the population of geckos was valid (lines 12–13). Do not include sample size as one of the required precautions. In your answer, include the formula to estimate the size of the population using the mark-release-recapture method. [3 marks] Precaution 1 Precaution 2 Formula END OF QUESTIONS 15 33 Do not write outside the box There are no questions printed on this page IB/M/Jun24/7402/2 DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED 34 Additional page, if required. Write the question numbers in the left-hand margin. Question number IB/M/Jun24/7402/2 Do not write outside the box 35 Additional page, if required. Write the question numbers in the left-hand margin. Question number IB/M/Jun24/7402/2 Do not write outside the box 36 Do not write outside the box IB/M/Jun24/7402/2 Question number Additional page, if required. Write the question numbers in the left-hand margin. Copyright information For confidentiality purposes, all acknowledgements of third-party copyright material are published in a separate booklet. This booklet is published after each live examination series and is available for free download from Permission to reproduce all copyright material has been applied for. In some cases, efforts to contact copyright-holders may have been unsuccessful and AQA will be happy to rectify any omissions of acknowledgements. If you have any queries please contact the Copyright Team. Copyright © 2024 AQA and its licensors. All rights reserved. A-level BIOLOGY 7402/2 Paper 2 Mark scheme June 2024 Version: 1.0 Final