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AQA A LEVEL (7402/2) BIOLOGY PAPER 2 QUESTION PAPER+ MARK
SCHEME JUNE 2024
A-level
BIOLOGY
Paper 2
Friday 14 June 2024 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. 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 91. For Examiner’s Use Question Mark 1 2 3 4 5 6 7 8 9 10 TOTAL
- IB/M/Jun24/G4006/E7 7402/
Do not write outside the box (^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 ►
Do not write outside the box (^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
Do not write outside the box (^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
Do not write outside the box (^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 ►
Do not write outside the box 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 ×
Do not write outside the box (^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]
Do not write outside the 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. Maximum number produced per fat hen plant during a growing season
Percentage viable (able to develop) after a growing season 79
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Do not write outside the
. (^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. High blood pressure 0. High LDL (Low-density lipoprotein) concentration
Hyperthyroidism 0. What can you conclude from Table 2? [3 marks] Turn over ►
Do not write outside the (^0 7). (^1) Bam H1 and Hin dIII are both restriction endonucleases. box 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 Bam H1. Experiment 2 – DNA cut into fragments using Bam H1 and Hin dIII.
Do not write outside the box (^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
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