AQA A-level BIOLOGY 7402/2 Paper 2 Version: 1.0 Final *jun* IB/M/Jun23/E13 7402/2QUESTION PAPER & MARKING SCHEME/ [MERGED] Marl( scheme June 2023

AQA A-level BIOLOGY 7402/2 Paper 2 Version: 1.0 Final *jun* IB/M/Jun23/E13 7402/2 For Examiner’s Use Question Mark 1 2 3 4 5 6 7 8 9 10 TOTAL Friday 16 June 2023 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. Please write clearly in block capitals. Centre number Candidate number Surname Forename(s) Candidate signature I declare this is my own work. A-level BIOLOGY Paper 2 2 *02* IB/M/Jun23/7402/2 Do not write outside the Answer all questions in the spaces provided. box 0 1 . 1 A student used chromatography to separate the different photosynthetic pigments in a chlorophyll solution. She had the following materials. Chromatography paper A ruler and pencil Suitable glassware A solvent (solvent A) 2 cm3 of the chlorophyll solution Describe how she could use these materials to separate the photosynthetic pigments by chromatography. [4 marks] 0 1 . 2 Using solvent A, the student separated five pigments. She then repeated her method using a different solvent, B. Using solvent B, she separated six pigments. Explain the difference between these results. [2 marks] 6 3 *03* Turn over ► IB/M/Jun23/7402/2 Do not write outside the box 0 2 . 1 Glutamate is a neurotransmitter involved in the transmission of nerve impulses from pain receptors to the brain. Ziconotide is a drug that can reduce severe, constant pain. Ziconotide blocks the calcium ion channels at some of the synapses which use glutamate. The transmission of glutamate at synapses is similar to that of acetylcholine. Explain how ziconotide reduces severe, constant pain. [5 marks] Ziconotide is a polypeptide and acts on synapses in the spinal cord. Scientists investigated the effectiveness of ziconotide in reducing severe, constant pain. Ziconotide was injected into each patient’s cerebrospinal fluid that bathes the brain and spinal cord. Patients recorded the intensity of their pain using a statistically valid scale. 0 2 . 2 Suggest two reasons why the patients had ziconotide injected into their cerebrospinal fluid rather than taking a pill containing the drug. [2 marks] 1 2 Question 2 continues on the next page 4 *04* IB/M/Jun23/7402/2 Do not write outside the box 0 2 . 3 Ziconotide was injected at 3 ng kg–1 h–1 for 8 days into each patient. 1 ng = 1 × 10–9 g Calculate the total mass in grams of ziconotide injected after 8 days into a patient with a body mass of 82 kg Show your working. [2 marks] Answer g 0 2 . 4 When the patients recorded the intensity of pain, suggest two reasons why it was important to use a statistically valid scale. [2 marks] 1 2 11 5 *05* Turn over ► IB/M/Jun23/7402/2 Do not write outside the 0 3 box Figure 1 shows part of a phosphorus cycle, including the mass of phosphorus in two stores. Figure 1 One teragram (Tg) is 1 × 1012 grams. The supply of phosphorus to the soil is shown as a percentage of the total phosphorus mass of each store. 0 3 . 1 Calculate in teragrams the difference in the supply of phosphorus to the soil from the two stores shown in Figure 1. Show your working. [2 marks] Answer Tg Question 3 continues on the next page 6 *06* IB/M/Jun23/7402/2 Do not write outside the Water shortage can inhibit crop production. box Scientists investigated the effect of the mycorrhizal species Glomus intraradices on the growth of tomato plants under conditions of water shortage and no water shortage. • The scientists planted tomato seeds into a large number of pots containing sterilised soil. • They added a culture of G. intraradices to 50% of the pots and 50% were left untreated. • After the seeds had developed into seedlings (young plants), the seedlings from the untreated and treated pots were planted into four separate large greenhouses (glasshouses). • A very limited supply of water (water shortage) was provided to two of the greenhouses. A sufficient supply of water (no water shortage) was provided to the other two greenhouses. • After 60 days, the scientists determined the mean mass of tomatoes (kg m–2) from each greenhouse. Greenhouse P – untreated seedlings with water shortage Greenhouse Q – treated seedlings with water shortage Greenhouse R – untreated seedlings with no water shortage Greenhouse S – treated seedlings with no water shortage Treated seedlings are plants grown with G. intraradices. Figure 2 shows the scientists’ results. The error bars represent ± 2 standard deviations from