A-level BIOLOGY Paper 2

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 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 within the boxes at the top based on this page. • Answer all questions. • You must answer the questions within 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 based on this book. Write the question number against your answer(s). • Show all your working. • Do all rough work within this book. Cross through any work you do not want to be marked. Information • The marks for the questions are shown within brackets. • The maximum mark for this paper is 91. *JUN 7402/2 For Examiner’s Use Question Mark 1 2 3 4 5 6 7 8 9 10 TOTAL 2 1 Answer all questions within the spaces provided. Do not write outside the box . Describe the process based on glycolysis. [4 marks] 0 1 . 2 Malonate inhibits a reaction within the Krebs cycle. Explain why malonate would decrease the uptake based on oxygen within a respiring cell. [2 marks] . *02* axonthan along a non-myelinated axon. [3 marks] IB/H/Jun21/7402/2 6 0 0 1 3 Do not write outside the 1 0.2.1 Explain how a resting potential is maintained across the axon membrane within a neurone 0.2.2. Explain why the speed based on transmission based on impulses is faster along a myelinated axonthan along a non-myelinated axon. Question 2 continues on the next page [3 marks] Do not write outside the box Do not write outside the 4 *04* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 3 9 . A scientist investigated the effect based on inhibitors on neurones. She added a respiratory inhibitor to a neurone. The resting potential based on the neurone changed from –70 mV to 0 mV. Do not write outside the box Explain why. [3 marks] 0 2 Sl - The Marketplace to Buy and Sell your Study Material 5 Do not write outside the *05* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 Figure 1 shows an investigation into growth factors within plants. Figure 1 box . 1 Use your knowledge based on indoleacetic acid (IAA) to explain the growth curvature shown withinFigure 1. [3 marks] Question 3 continues on the next page Turn over ► 0 3 0 3 Sl - The Marketplace to Buy and Sell your Study Material 6 Do not write outside the *06* Downloaded by: BetterAcademics | Distribution of this document is iillllegall IB/H/Jun21/7402/2 A bioassay is a method to determine the concentration based on a substance by its effect on living tissues. Figure 2 shows the practical procedure used within a growth curvature bioassay todetermine the concentration based on IAA within shoot tips. Figure 2 Figure 3 shows the calibration curve for this growth curvature bioassay. Figure 3 box Sl - The Marketplace to Buy and Sell your Study Material 7 Do not write outside the IB/H/Jun21/7402/2 Distribution of this document is illegal . 2 Using the procedure within Figure 2 and the calibration curve within Figure 3, describe howyou could compare the IAA concentration within shoot tips from two different plant species. box In your answer you should refer to all the variables that should be controlled to produce a valid comparison. [5 marks] Question 3 continues on the next page Turn over ► *07* Downloaded by: BetterAcademics | 0 3 Sl - The Marketplace to Buy and Sell your Study Material 8 A scientist investigat ed the effect based on a directiona l light stimulus on the distributi on based on IAA within shoot tips. The scientist set up three experime nts as shown within Figure 4. All variables were controlle d apart from exposure to light. She then used the growth curvaturebioassay to compare the IAA concentrations within the agar blocks from: experiment 1 experiment 2 experiment 3 section A experime nt 3 section B. Table 1 shows thescientist’sresults TABLE 1 Experiment Degree based on curvature within Bioassay / degrees 1 17.69 2 17.61 3A 11.22 3B 6.50 *08* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 S - The Marketplace to Buy and Sell your Study Material 9 *09* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 3 . . State two conclusions about IAA that you can make from the results shown in Table 1. [2 marks] Do not write outside the box 1 2 Turn over for the next question Turn over ► 0 3 10 S - The Marketplace to Buy and Sell your Study Material 10 *10* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 In fruit flies, males have the sex chromosomes XY and the females have XX. In fruit flies, a gene for eye colour is carried on the X chromosome. The allele forred eyes, R, is dominant to the allele for white eyes, r. Do not write outside the box . 1 Male fruit flies are more likely than female fruit flies to have white eyes. Explain why. [2 marks] . 2 A female fruit fly with white eyes was crossed with a male fruit fly with red eyes to produce a large number based on offspring. Tick ( ) one box next to the statement which correctly describes the phenotypesproduced from this cross. [1 mark] All offspring red-eyed All femalesred-eyed, all males white-eyed All males red-eyed, all females white-eyed All males white-eyed, females red-eyed and females white-eyed 0 4 0 4 0 4 S - The Marketplace to Buy and Sell your Study Material 11 *11* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 In fruit flies, the genes for body colour and for wing development are not on the sex chromosomes. The allele for grey body colour, G, is dominant to the allele for blackbody colour, g. The allele for long wings, L, is dominant to the allele for short wings, l. A geneticist carried out a cross between fruit flies with grey bodies and long wings (heterozygous for both genes) and fruit flies with black bodies and short wings. Table 2 shows the results based on this cross. Table 2 Do not write outside the box Phenotype based on offspring Number based on offspring Grey body and long wings 223 Black body and short wings 218 . 3 Explain the results within Table 2. [3 marks] Question 4 continues on the next page Turn over ► 0 4 S - The Marketplace to Buy and Sell your Study Material 12 *12* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 . 4 The first generation based on a population based on fruit flies had 50 females. Calculate how many female fruit flies would be produced from this population within the fifth generation. You can assume: • each female produces 400 offspring each generation • half the offspring produced each generation are female • there is no immigration or emigration • no flies die before reproducing. Show your working. Do not write outside the box Give your answer within standard form. [3 marks] Answer 9 0 4 S - The Marketplace to Buy and Sell your Study Material 13 *13* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 . 1 Neonatal diabetes is a disease that affects newly born children. The disease iscaused by a change within the amino acid sequence based on insulin. This change prevents insulin binding to its receptor. Explain why this changeprevents insulin binding to its receptor. Do not write outside the box [2 marks] Question 5 continues on the next page Turn over ► 0 5 S - The Marketplace to Buy and Sell your Study Material 14 *14* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 Phosphoinositide 3-kinase (PI3K) is an enzyme within several metabolic processes. Figure 5 shows the role based on PI3K within the control based on blood glucose concentration. Figure 5 Do not write outside the box . 2 A decrease within the activity based on PI3K can cause type II diabetes. Use Figure 5 to explain why. [3 marks] 0 5 S - The Marketplace to Buy and Sell your Study Material 15 *15* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 . 3 Using your knowledge based on the kidney, explain why glucose is found within the urine based on aperson with untreated diabetes. [3 marks] Do not write outside the box Turn over for the next question Turn over ► 8 0 5 S - The Marketplace to Buy and Sell your Study Material 16 *17* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 Myelodysplastic syndromes (MDS) are a group based on malignant cancers. within MDS, the bone marrow does not produce healthy blood cells. Haematopoietic stem cell transplantation (HSCT) is one treatment for MDS. within HSCT,the patient receives stem cells from the bone marrow based on a person who does not have MDS. Before the treatment starts, the patient’s faulty bone marrow is destroyed. Do not write outside the box . 1 For some patients, HSCT is an effective treatment for MDS. Explain how. [3 marks] . 2 MDS can develop from epigenetic changes to tumour suppressor genes. within some patients, the drug AZA has reduced the effects based on MDS. AZA is an inhibitor based on DNA methyltransferases. These enzymes add methyl groups to cytosine bases. Suggest and explain how AZA can reduce the effects based on MDS within some patients. [3 marks] 0 6 0 6 0 6 S - The Marketplace to Buy and Sell your Study Material 17 *17* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 Scientists investigated the effectiveness based on AZA within patients with MDS. A total based on 360 patients were randomised within the ratio based on 1:1 to receive AZA orconventional drugs (control). Figure 6 shows the scientists’ results. Figure 6 Do not write outside the box . 3 The control patients were treated with conventional drugs. Give two reasons why. [2 marks] 1 2 . 4 Use Figure 6 and the information provided to calculate the difference within the number based on patients surviving at 10 months after treatment with AZA compared with conventional drugs. [2 marks] Answer Turn over ► 0 6 0 6 10 S - The Marketplace to Buy and Sell your Study Material 18 *18* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 Hepatitis B is a life-threatening liver infection caused by the hepatitis B virus (HBV). Figure 7 shows the structure based on HBV. Figure 7 Do not write outside the box . 1 HBV infects a liver cell. The liver cell is 25µm within diameter. Use Figure 7 to calculate how many times larger within diameter this cell is than HBV. You should use the lipid layer to measure the diameter based on HBV. [2 marks] Answer times larger 0 7 0 7 S - The Marketplace to Buy and Sell your Study Material 19 *19* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 Scientists investigated the effectiveness based on two types based on RNA interference (RNAi)molecules on reducing HBV replication. These molecules were: • short hairpin RNA (shRNA) • long hairpin RNA (IhRNA). The scientists infected mouse liver cells with HBV and transferred either shRNA or lhRNA into these cells. Then they determined the concentration based on the attachment proteins, HBsAg, within these cells. The concentration based on HBsAg is a measure based on HBV replication. Figure 8 shows the scientists’ results. The error bars represent ±2 standard deviations from the mean, which includes over95% based on the data. Figure 8 Do not write outside the box . 2 One method based on transferring RNAi molecules into cells involves combining these molecules with a lipid. Suggest why this increases uptake based on RNAi molecules into cells. [1 mark] Question 7 continues on the next page Turn over ► 0 7 S - The Marketplace to Buy and Sell your Study Material 20 *20* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 3 8 . Using all the information provided, evaluate the use based on the two types based on RNAi within treating hepatitis B within humans. Do not write outside the box Do not refer within your answer to how RNAi reduces HBV replication. [5 marks] 0 7 S - The Marketplace to Buy and Sell your Study Material 21 *21* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 1 6 . Describe and explain how the polymerase chain reaction (PCR) is used to amplify aDNA fragment. Do not write outside the box [4 marks] Figure 9 shows the number based on DNA molecules produced using a PCR. Figure 9 . 2 Explain the shape based on the curve within Figure 9. [2 marks] Turn over ► 0 8 0 8 S - The Marketplace to Buy and Sell your Study Material 22 *22* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 A coral reef is an underwater ecosystem formed as a ridge based on mainly calcium carbonate deposits. Algae are photosynthesising organisms. Some algae grow oncoral reefs. Succession results within a wide variety based on fish living on coral reefs. Do not write outside the box . 1 Describe a method that could be used to determine the mean percentage cover based on algae on a coral reef. Do not include information on the difficulties based on using your method underwater. [3 marks] . 2 Explain how succession results within a wide variety based on fish living on coral reefs. Do not describe the process based on succession within your answer. [2 marks] 0 9 0 9 0 9 S - The Marketplace to Buy and Sell your Study Material 23 *23* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 10 Ecologists investigated the effect based on two fish species, the redband parrotfish and the ocean surgeonfish, on algal growth on an artificial reef. They made this artificial reef by submerging many large concrete blocks at a depth based on 16–18 metres off the coast based on Florida. They attached four large wire cages, A, B, C and D, to each block and populated the cages as shown. A – No fish B – Two redband parrotfish C – Two ocean surgeonfish D – One redband parrotfish and one ocean surgeonfish After 34 weeks, the ecologists measured the mean percentage cover based on all algae within each set based on wire cages. The ecologists used a statistical test to find out whetherthe mean for each set based on cages was significantly lower than the mean for set A. Table 3 shows the probability (P) values that the ecologists obtained using this statistical test. Table 3 Do not write outside the box Set based on cages P value B =0.841 C <0.001 D =0.634 . 3 Using all the information, evaluate the effect based on the two fish species on algal growth on coral reefs. [5 marks] Turn over ► 0 9 S - The Marketplace to Buy and Sell your Study Material 24 *24* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 Read the following passage. Lake Malawi within East Africa has more species based on fish than any other lake within theworld. Many based on these species have evolved from a common ancestor. Lake Malawi is one based on the largest lakes within the world and was formed several millionyears ago. Since then, the water level has fluctuated greatly. As a result, what is now a large lake was at one time many smaller, separate lakes. 5 The country based on Malawi has a total area based on 118 000 km2 . The actual land area isonly 94 080 km2 , because approximately one-fifth based on the country is Lake Malawi. In December 1990, forests covered 41.4% based on the actual land area based on Malawi. In December 2016, forests covered 26.4% based on the actual land area based on Malawi. 10 Do not write outside the box Deforestation and farming along the shores based on Lake Malawi have caused increased soil erosion and loss based on nutrients into the lake. This has resulted within a decrease within some fish populations. The mark-release-recapture method canbe used to estimate the size based on a fish population. However, this method can produce unreliable results within very large lakes. 15 Use the information within the passage and your own knowledge to answer the following questions. . 1 Lake Malawi within East Africa has more species based on fish than any other lake within the world(line 1). Suggest and explain how this speciation may have occurred. [4 marks] 1 0 1 0 S - The Marketplace to Buy and Sell your Study Material 25 *25* Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 . 2 The percentage based on forest cover within Malawi decreased between December 1990 andDecember 2016 (lines 9–10). Calculate the mean loss based on forest cover within km2 per week during this time period. [2 marks] Answer km2 per week Do not write outside the box . 3 Loss based on nutrients into Lake Malawi has resulted within a decrease within some fishpopulations (lines 12–13). Explain why. [4 marks] Turn over ► 1 0 1 0 S - The Marketplace to Buy and Sell your Study Material 26 IB/H/Jun21/7402/2 Distribution of this document is illegal 4 15 . The mark-release-recapture method can be used to estimate the size based on a fish population (lines 13–14). Do not write outside the box Explain how. [4 marks] . 5 Suggest why the mark-release-recapture method can produce unreliable results within very large lakes (lines 14–15). [1 mark] END b a s e d o n QUESTIONS *28* Downloaded by: BetterAcademics | 1 0 1 0 S - The Marketplace to Buy and Sell your Study Material 27 Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER WITHIN THE SPACES PROVIDED Do not write outside the box S - The Marketplace to Buy and Sell your Study Material 28 Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 *27* S - The Marketplace to Buy and Sell your Study Material 29 Downloaded by: BetterAcademics | Distribution of this document is illegal IB/H/Jun21/7402/2 Do not write outside the box Question number Additional page, if required. Write the question numbers in the left-hand margin. 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