page 20 [BLANK PAGE] DO NOT WRITE ON THIS PAGE Acknowledgement of copyright Question 5 Natsmith1/shutterstock.com H FOR OFFICIAL USE Fill in these boxes and read what is printed below. Number of seat Town © Mark Full name of centre Forename(s) Surname Scottish candidate number Date of birth Year Day Month National Qualications 2019 Instructions for the completion of Paper 1 are given on page 02. Record your answers on the answer grid on page 03. You may use a calculator. Use blue or black ink. Before leaving the examination room you must give your answer booklet to the Invigilator; if you do not, you may lose all the marks for this paper. X807/76/02 TUESDAY, 30 APRIL 09:00 AM – 09:40 AM A/SA Biology Paper 1 — Multiple choice Answer booklet page 02 Paper 1 — 25 marks The questions for Paper 1 are contained in the question paper X807/76/12. Read these and record your answers on the answer grid on page 03. Use blue or black ink. Do NOT use gel pens or pencil. 1. The answer to each question is either A, B, C or D. Decide what your answer is, then fill in the appropriate bubble (see sample question below). 2. There is only one correct answer to each question. 3. Any rough working should be done on the additional space for answers and rough work at the end of this booklet. Sample question The thigh bone is called the A humerus B femur C tibia D fibula. The correct answer is B — femur. The answer B bubble has been clearly filled in (see below). A B C D Changing an answer If you decide to change your answer, cancel your first answer by putting a cross through it (see below) and fill in the answer you want. The answer below has been changed to D. A B C D If you then decide to change back to an answer you have already scored out, put a tick (3) to the right of the answer you want, as shown below: A B C D or A B C D page 03 Paper 1 — Answer grid A B C D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Biology page 04 [BLANK PAGE] DO NOT WRITE ON THIS PAGE H FOR OFFICIAL USE Fill in these boxes and read what is printed below. Number of seat Town © Mark Full name of centre Forename(s) Surname Scottish candidate number Date of birth Year Day Month National Qualications 2019 Total marks — 95 Attempt ALL questions. You may use a calculator. Questions 3 and 16 contain a choice. Write your answers clearly in the spaces provided in this booklet. Additional space for answers and rough work is provided at the end of this booklet. If you use this space you must clearly identify the question number you are attempting. Any rough work must be written in this booklet. Score through your rough work when you have written your final copy. Use blue or black ink. Before leaving the examination room you must give this booklet to the Invigilator; if you do not, you may lose all the marks for this paper. X807/76/01 TUESDAY, 30 APRIL 10:10 AM – 12:30 PM B/SA Biology Paper 2 page 02 MARKS DO NOT WRITE IN THIS MARGIN Total marks — 95 Attempt ALL questions Questions 3 and 16 contain a choice. 1. The diagram shows the replication of DNA in a chromosome from a eukaryotic cell. The arrows show the directions of replication. 3′ 5′ primer protein X (a) Name protein X. (b) Explain why primers are necessary for DNA replication. (c) (i) Explain why only the leading strand can be replicated continuously. (ii) Name the enzyme that joins fragments together in the lagging strand. (d) Describe how DNA is organised in prokaryotes. 1 1 1 1 2 page 03 MARKS DO NOT WRITE IN THIS MARGIN 2. Three different mutated bacteria, X, Y and Z were studied. Each had a mutation in a different region of its DNA that is transcribed to rRNA. Protein synthesis was measured in cultures of each mutated bacteria and in a culture of unmutated bacteria. The results are shown in the table. Bacterial culture Protein synthesis (%) Unmutated 100 X 9 Y 15 Z 90 (a) Calculate the simplest whole number ratio of percentage protein synthesis in cultures X, Y and Z. Space for calculation : : (b) Name the other component of ribosomes, apart from rRNA. (c) Using your knowledge of biology, suggest how a change in the sequence of bases in DNA transcribed to rRNA in the mutated cultures resulted in a decrease in protein synthesis. (d) Describe one structural difference between DNA and rRNA. 1 1 2 1 [Turn over page 04 MARKS DO NOT WRITE IN THIS MARGIN 3. Attempt either A or B. Write your answer in the space below. A Write an account of ATP synthesis in the electron transport chain during cellular respiration. OR B Write an account of competitive and feedback inhibition of enzymes. You may use labelled diagrams where appropriate. 4 4 page 05 MARKS DO NOT WRITE IN THIS MARGIN 4. Myoglobin and haemoglobin are oxygen-binding proteins in mammals. The myoglobin molecule is a single globin polypeptide. The haemoglobin molecule is composed of both alpha globin and beta globin polypeptides. (a) Myoglobin consists of a chain of 154 amino acids folded in a specific three-dimensional shape. (i) Name a bond that holds the polypeptide chain in this shape. (ii) The gene for myoglobin contains 1154 bases while its mature mRNA transcript contains 462 bases. Give a reason for this difference. (b) The genes for myoglobin and haemoglobin have evolved from a single ancestral globin gene as shown in the diagram. ancestral globin gene beta globin gene myoglobin alpha globin gene myoglobin gene haemoglobin beta globin alpha globin In the genome of mammals there are multiple copies of alpha and beta globin genes. (i) The multiple copies of alpha and beta globin genes are the result of duplication mutations. Describe how a duplication mutation occurs. (ii) Explain the importance of duplication mutations in evolution. 1 1 1 2 [Turn over page 06 MARKS DO NOT WRITE IN THIS MARGIN 5. The Galapagos are a group of islands 600 to 800 miles off the coast of South America. Less than three million years ago some finches of a single ancestral species reached these islands from South America and bred successfully. The number of islands has increased over time, further isolating groups of finches. (a) Use this information to name the type of isolation barrier involved in the speciation of these finches and explain its role. Name Explanation (b) The table shows the estimated number of islands and finch species in the Galapagos over the last 2·8 million years. Time (millions of years ago) Estimated number of islands in the group Estimated number of finch species present 2·8 4 0 1·0 6 5 0·5 18 9 0·0 18 14 (i) Calculate the average increase in the number of finch species per million years over this entire period. Space for calculation species per million years 2 1 page 07 MARKS DO NOT WRITE IN THIS MARGIN 5. (b) (continued) (ii) Suggest what could have caused the change in the number of finch species over the last 0·5 million years. (c) A molecular clock was used to estimate the dates of the divergence of each species. Give one example of the type of data required to generate a molecular clock. [Turn over 1 1 page 08 MARKS DO NOT WRITE IN THIS MARGIN 6. Cystic fibrosis in humans is caused by mutations in a gene that reduces chloride transport across the cell membrane. An investigation was carried out to determine the effectiveness of two drugs, P and Q, on improving chloride transport in individuals with cystic fibrosis. Individuals with different mutations, A, B, and both A and B, were treated as follows. • No drugs • Drug P alone • Drug Q alone • Drug P and drug Q combined Chloride transport across cell membranes was measured and compared to the chloride transport in a control group with no mutations in the gene. The results are shown in the graph. Treatment drug P no drugs drug Q average chloride transport (% of control) drugs P + Q mutation B A 60 50 40 30 20 10 0 both A + B (a) State the purpose of including a control group in this investigation. 1 page 09 MARKS DO NOT WRITE IN THIS MARGIN 6. (continued) (b) Identify the treatment and mutation for which the drug(s) had no effect. Treatment Mutation (c) State how the graph shows that each treatment was carried out on more than one individual with each mutation. (d) State the term used to describe the selection of drugs to treat individuals based on their genomic sequence. [Turn over 2 1 1 page 10 MARKS DO NOT WRITE IN THIS MARGIN 7. The genome of all organisms contains both protein coding genes and non-coding DNA. The size of the genome varies between different species. The table shows the size of the genome and the number of protein coding genes in several different organisms. Organism Size of genome (base pairs) Number of protein coding genes Eukaryotes yeast 1·2 × 107 6600 fruit fly 1·4 × 108 14 000 human 3·2 × 109 21 000 Prokaryotes V. cholera 4·0 × 106 3900 E. coli 4·6 × 106 4200 (a) (i) Using information from the table, compare the size of genomes of eukaryotes and prokaryotes. (ii) Calculate how many times greater the human genome is compared to the V. cholera genome. Space for calculation times greater (iii) The prokaryote M. tuberculosis has a genome size of 4·4 × 106 base pairs. Predict the number of protein coding genes in M. tuberculosis. 1 1 1 page 11 MARKS DO NOT WRITE IN THIS MARGIN 7. (continued) (b) Protein coding genes are used to produce mRNA, which is translated into protein. The bar graph shows the percentage of the genome that codes for protein in four of the organisms shown in the table. V. cholera E. coli yeast fruit fly organism 100 90 80 70 60 50 40 30 20 10 0 percentage of genome coding for protein Use the information in the table and the graph to calculate the size of the genome coding for protein in a fruit fly. Space for calculation base pairs (c) Give one role of the non-coding DNA in the genome. (d) In eukaryotes, alternative RNA splicing occurs. Explain how this results in different proteins being expressed from a single gene. 1 1 1 [Turn over page 12 MARKS DO NOT WRITE IN THIS MARGIN 8. The bacterium E.coli was cultured in a growth medium containing 0·6 mM glucose and 0·6 mM lactose for 180 minutes. Glucose and lactose concentrations were measured every 20 minutes. The results are shown in the table. Time (minutes) Glucose concentration (mM) Lactose concentration (mM) 0 0·60 0·60 20 0·50 0·60 40 0·38 0·60 60 0·09 0·60 80 0·00 0·55 100 0·00 0·44 120 0·00 0·32 140 0·00 0·15 160 0·00 0·04 180 0·00 0·00 (a) Using values from the table, describe changes in the concentration of lactose over the 180 minutes of the experiment. 2 page 13 MARKS DO NOT WRITE IN THIS MARGIN 8. (continued) (b) E.coli breaks down lactose using the enzyme beta-galactosidase as shown. beta-galactosidase lactose glucose + galactose Beta-galactosidase is produced by E.coli only when lactose is present and glucose is absent. (i) Using information from the table, identify the time when E.coli started producing beta-galactosidase. minutes (ii) Suggest a benefit to E.coli of producing beta-galactosidase only when lactose is present. (c) In terms of activation energy, state how enzymes increase the rates of reactions in living cells. [Turn over 1 1 1 page 14 MARKS DO NOT WRITE IN THIS MARGIN 9. Respiration is a cellular process that produces ATP. The first stage in this process is glycolysis. Some steps of glycolysis are shown in the diagram. Pyruvate NAD ATP NADH ADP ADP Step 2 ATP Intermediates Glucose Step 1 (a) State the exact location of glycolysis. (b) (i) Describe the role of ATP in Step 1. (ii) Explain how glycolysis results in a net gain of ATP. (iii) Describe the role of dehydrogenase enzymes in the conversion of intermediates to pyruvate. 1 1 1 2 page 15 MARKS DO NOT WRITE IN THIS MARGIN 9. (continued) (c) When fermentation occurs in animal cells, pyruvate is converted to lactate as shown. pyruvate + NADH lactate + NAD (i) State the conditions required for fermentation. (ii) Using all the information given, suggest why the conversion of pyruvate to lactate is required for glycolysis to continue. [Turn over 1 1 page 16 MARKS DO NOT WRITE IN THIS MARGIN 10. The fungus Aspergillus niger (A.niger) is used to produce citric acid in fermenters using sugars as substrates. Citric acid is an intermediate in a metabolic pathway as shown. isocitrate citric acid aconitase enzyme enzymes enzymes intermediates sugars (a) The aconitase enzyme requires iron to function. Explain why the growth medium used to produce citric acid should not contain iron. (b) The optimum temperature for citric acid production by A.niger is 30 °C. Explain why less citric acid would be produced if the temperature in the fermenter was reduced. 1 1 page 17 MARKS DO NOT WRITE IN THIS MARGIN 10. (continued) (c) A.niger was grown in a fermenter over an 8 day period and the pH was measured every 2 days. The results are shown in the graph. 8 7 time (days) 6 6 5 0 4 4 2 3 pH (i) Predict the pH at 10 days. (ii) Suggest a reason for the change in the pH observed. (iii) State a variable, other than temperature or pH, that should be monitored and controlled in this process. (iv) Explain why it was necessary to sterilise the fermenter before A.niger was added. [Turn over 1 1 1 2 page 18 MARKS DO NOT WRITE IN THIS MARGIN 11. Djungarian hamsters (Phodopus sungorus) are small mammals with high metabolic rates. Under certain conditions they will enter torpor. An experiment was carried out to investigate the effect of daily food intake on torpor frequency. Four groups of six hamsters were fed different masses of food each day and the number of times they entered torpor in one week was recorded. The results are shown in the table. Group Mass of food eaten each day (g) Average torpor frequency (number of times entering torpor in the week) 1 2·5 42 2 3·0 25 3 3·5 15 4 4·0 7 (a) State an advantage to the hamsters of entering torpor. (b) Suggest a measurement that could have been taken to determine whether the hamsters had entered torpor. (c) The average time spent in each period of torpor was 120 minutes. Calculate the average time spent in torpor per day by a hamster with a daily food intake of 2·5 g. Space for calculation minutes 1 1 1 page 19 MARKS DO NOT WRITE IN THIS MARGIN 11. (continued) (d) State how the design of the experiment ensured that the results were reliable. (e) Suggest a factor, other than daily food intake, which could affect torpor frequency. (f) Daily torpor is a way in which animals survive adverse conditions. Give one way in which animals avoid adverse conditions. [Turn over 1 1 1 page 20 MARKS DO NOT WRITE IN THIS MARGIN 12. An investigation was carried out into the effect of increasing time of exposure to UV light on the survival of wild type (WT) and mutant (M) yeast cells. Each type of yeast cell was grown in separate liquid media at 30 °C for 24 hours, diluted and plated onto separate agar plates. They were then exposed to a UV light source for between 0 and 30 seconds in a darkened room. The plates were incubated for four days at 20 °C and the number of yeast colonies that had grown was counted. Each colony grew from a single cell. The results are shown in the table. Time of exposure to UV light (seconds) Number of yeast colonies WT M 0 360 400 5 210 120 10 90 25 15 45 10 20 20 0 30 10 0 (a) (i) State an independent variable in this experiment. (ii) Suggest why exposure to UV light was carried out in a darkened room. 1 1 page 21 MARKS DO NOT WRITE IN THIS MARGIN 12. (continued) (b) On the grid, draw a line graph using the results in the table for both WT yeast and M yeast. (Additional graph paper, if required, can be found on page 31) (c) Draw one conclusion from the results of this investigation. (d) Sunscreen lotions can protect cells from UV damage. Suggest how the investigation could be modified to test the effectiveness of a sunscreen lotion using M yeast as model cells. [Turn over 3 1 2 page 22 MARKS DO NOT WRITE IN THIS MARGIN 13. Apples and plums are grown in North America as food crops. Brown stink bugs (Halyomorpha halys) feed on apples and plums reducing fruit yield. Insecticides are often sprayed onto fruit crops to help control these pests. (a) State how the use of insecticides can be harmful to the environment. (b) Wheel bugs (Arilus cristatus) are a species of insect native to North America that prey on many different insects, including brown stink bugs. Wheel bugs are used along with insecticides to reduce the number of brown stink bugs. (i) Explain why this method of control would require the use of less insecticide. (ii) Name the method of control that involves using both insecticides and wheel bugs. (c) If brown stink bugs spread to the UK, introducing the non-native wheel bugs from North America could be used as a method of control. If this method of control was used, wheel bugs could become an invasive species. (i) Describe evidence that could suggest the wheel bugs had become an invasive species. (ii) Give one reason why invasive species are more successful in their new habitat. 1 1 1 2 1 page 23 [Turn over for next question DO NOT WRITE ON THIS PAGE page 24 MARKS DO NOT WRITE IN THIS MARGIN 14. A tick is a small invertebrate. Some ticks carry the bacteria Borrelia burgdorferi (B.burgdorferi) in their gut after biting infected animals. If these ticks bite humans to feed on blood, the bacteria may enter the human bloodstream and cause Lyme disease. (a) Use the information given to suggest why ticks can be described as (i) vectors (ii) parasites. 1 1 page 25 MARKS DO NOT WRITE IN THIS MARGIN 14. (continued) (b) The tables show the average global temperatures between 1981 and 2010, and the number of cases of Lyme disease in the UK between 1999 and 2009. Table 1 Table 2 Year Average global temperature (°C) Year Number of cases of Lyme disease in the UK 1981–1990 14·12 1999 200 1991–2000 14·26 2004 515 2001–2010 14·47 2009 870 (i) Calculate the percentage increase in cases of Lyme disease in the UK between 1999 and 2009. Space for calculation % (ii) It was concluded from the information in Table 1 and Table 2 that the increase in the number of cases of Lyme disease in the UK was caused by an increase in temperature. Suggest why this conclusion may not be valid. (c) Two methods used to reduce the number of cases of Lyme disease in humans were suggested. Method 1 Use pesticide to kill ticks Method 2 Treat infected animals with antibiotics Explain how each method could reduce the number of cases of Lyme disease in humans. Method 1 Method 2 1 1 2 [Turn over page 26 MARKS DO NOT WRITE IN THIS MARGIN 15. White-faced capuchin monkeys (Cebus capucinus) are primates that live in large social groups in tree tops in South America. Their predators include humans, birds of prey and snakes. If a capuchin sees a predator it gives an alarm call to warn others in the group. Capuchins give a different alarm call for each predator they encounter. Scientists recorded these alarm calls from adult monkeys. The results are shown in the table. Predator Total number of encounters Percentage of encounters when only one monkey called Percentage of encounters when more than one monkey called Birds of prey 155 60 40 Humans 12 67 33 Snakes 65 15 85 (a) (i) Calculate the number of encounters with birds of prey when only one monkey called. Space for calculation (ii) Using the information given, suggest why the highest number of encounters were with birds of prey. (b) Explain why giving alarm calls can be described as altruistic behaviour. 1 1 2 page 27 MARKS DO NOT WRITE IN THIS MARGIN 15. (continued) (c) Primates, such as capuchin monkeys, have a long period of parental care. Explain why the scientists only recorded the calls from adult monkeys. (d) Primates often form alliances with others and carry out appeasement behaviour within their group. State the advantages of these behaviours. Forming alliances Appeasement [Turn over for next question 1 2 page 28 MARKS DO NOT WRITE IN THIS MARGIN 16. Attempt either A or B. Write your answer in the space below and on pages 29 and 30. A Write notes on photosynthesis under the following headings. (i) Use of energy absorbed by photosynthetic pigments (ii) Carbon fixation OR B Write notes on the effects of the following on biodiversity. (i) The bottleneck effect (ii) Habitat fragmentation and habitat corridors You may use labelled diagrams where appropriate. 3 4 2 5 page 29 MARKS DO NOT WRITE IN THIS MARGIN SPACE FOR ANSWERS [Turn over page 30 MARKS DO NOT WRITE IN THIS MARGIN SPACE FOR ANSWERS [END OF QUESTION PAPER] page 31 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK ADDITIONAL GRAPH PAPER FOR QUESTION 12 (b) page 32 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK Acknowledgement of copyright Question 14 nechaevkon/shutterstock.com