Page 12 20. Some species of social insect are of economic importance to humans by providing ecosystem services. Which of the following are examples of ecosystem services? 1 Braconid wasps parasitising hornworms which are a pest of tomatoes. 2 Bumblebees pollinating an orchard of apple trees. 3 Worker termites caring for the queen and her offspring. A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3 [END OF SECTION 1. NOW ATTEMPT THE QUESTIONS IN SECTION 2 OF YOUR QUESTION AND ANSWER BOOKLET.] 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 2017 Total marks — 100 SECTION 1 — 20 marks Attempt ALL questions. Instructions for the completion of Section 1 are given on Page 02. SECTION 2 — 80 marks Attempt ALL questions. Questions 10 and 15 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. You should 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. X707/76/01 TUESDAY, 23 MAY 9:00 AM – 11:30 AM A/HTP Biology Section 1 — Answer Grid and Section 2 Page 02 SECTION 1 — 20 marks The questions for Section 1 are contained in the question paper X707/76/02. Read these and record your answers on the answer grid on Page 03 opposite. 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 A B C D 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 SECTION 1 — Answer Grid [Turn over Page 04 [BLANK PAGE] DO NOT WRITE ON THIS PAGE Page 05 [Turn over for next question DO NOT WRITE ON THIS PAGE Page 06 MARKS DO NOT WRITE IN THIS MARGIN SECTION 2 — 80 marks Attempt ALL questions Note that Questions 10 and 15 contain a choice 1. The diagram illustrates steps in the transcription and translation of a gene. Protein B Protein A Alternative splicing Gene DNA Primary mRNA transcript Exon 3 Exon 2 Exon 1 Exon 4 Exon 4 Exon 2 Exon 1 Exon 3 Exon 2 Exon 1 (a) Name the regions always removed from a primary mRNA transcript. (b) Insert numbers in the boxes below to show the three exons in the gene shown above which could be translated to produce a protein which is different from proteins A and B. Exon Exon Exon 1 1 Page 07 MARKS DO NOT WRITE IN THIS MARGIN 1. (continued) (c) Single gene mutations can occur which may affect the structure of the proteins produced. (i) Describe the effect of a nonsense mutation on Protein A and give a reason for your answer. Description Reason (ii) A deletion mutation occurred in Exon 2. Explain why this would have a major effect on the structure of proteins A and B. [Turn over 2 1 Page 08 MARKS DO NOT WRITE IN THIS MARGIN 2. Two heat-tolerant DNA polymerases used in polymerase chain reactions (PCR) are Taq and Pfu. Pfu has “proof reading” activity. It checks that the correct nucleotides are inserted during replication of a target sequence and then corrects any errors. The graph shows the temperatures during a single PCR cycle required to amplify a target sequence using Taq and Pfu. 4·0 3·5 3·0 2·5 2·0 1·5 1·0 0·5 0 100 90 80 70 60 50 40 Taq polymerase Pfu polymerase Key: Time (minutes) Temperature (°C) (a) (i) Calculate the time taken for 16 copies of the target sequence to be made from one DNA fragment using Taq polymerase. Space for calculation minutes 1 Page 09 MARKS DO NOT WRITE IN THIS MARGIN 2. (a) (continued) (ii) Identify the time period during which primers bind to the original DNA fragment. from to minutes. (b) A scientist was planning to amplify DNA using PCR. State which DNA polymerase should be used and describe the advantage of using this polymerase. DNA polymerase Advantage (c) Explain the importance of using heat-tolerant DNA polymerases in PCR. [Turn over 1 1 1 Page 10 MARKS DO NOT WRITE IN THIS MARGIN 3. The herbicide glyphosate is used to control the annual weed charlock (Sinapis arvensis) in cereal fields. An investigation was carried out into the effect of glyphosate on the development of glyphosate resistance in charlock plants in a cereal plot. The charlock plants were treated with glyphosate from 2009 to 2016 and the percentage of glyphosate resistant plants in the plot was recorded every year. The results are shown in the table. Year Charlock plants resistant to glyphosate (%) 2009 10 2010 18 2011 32 2012 42 2013 53 2014 58 2015 66 2016 66 (a) Using values from the table describe the change in glyphosate resistance over the time of investigation. (b) Explain how natural selection resulted in the change in glyphosate resistance. (c) Another investigation was carried out into the development of antibiotic resistance in bacteria. It was observed to be more rapid than the development of glyphosate resistance in charlock. Explain this observation in terms of gene transfer. 2 2 1 Page 11 MARKS DO NOT WRITE IN THIS MARGIN 4. (a) Human muscles contain satellite cells within the muscle tissue. The diagram illustrates the division and differentiation of satellite cells. satellite cell differentiation muscle cells myoblast cell cell division satellite cells (i) Using information from the diagram explain why satellite cells are an example of tissue (adult) and not embryonic stem cells. (ii) State one benefit to the human body of satellite cells differentiating into myoblast cells. (iii) Satellite cells could be used to treat muscle diseases. Give one ethical reason for using satellite cells instead of embryonic stem cells in order to treat such diseases. (b) Give one example of how stem cells are used as model cells in medical research. [Turn over 1 1 1 1 Page 12 MARKS DO NOT WRITE IN THIS MARGIN 5. (a) The phylogenetic tree illustrates the evolutionary relatedness of six groups of animals. 600 500 400 300 200 100 0 Salmon Frogs Eagles Humans Rats Mice Millions of years ago (i) Using information from the phylogenetic tree state when the last common ancestor of salmon and frogs lived. million years ago (ii) Calculate how many million years separate the divergence of eagles and humans from the divergence of rats and mice. Space for calculation million years (iii) Rats are more closely related to humans than they are to frogs. Use evidence from the phylogenetic tree to justify this statement. 1 1 1 Page 13 MARKS DO NOT WRITE IN THIS MARGIN 5. (continued) (b) The graph shows a molecular clock which compares the amino acid sequence of the protein cytochrome c between a range of species. 600 500 400 300 200 100 0 30 20 10 0 Amino acids in cytochrome c which are different (%) Time of last common ancestor (millions of years ago) (i) Cytochrome c is a protein containing 112 amino acids. Calculate the number of amino acids in cytochrome c that are different between two species whose last common ancestor lived 500 million years ago. Space for calculation (ii) Predict the percentage of amino acids in cytochrome c which would be different between two species who shared a common ancestor 550 million years ago. % (c) Using information from the phylogenetic tree and the graph, state the percentage of amino acids in cytochrome c that are different between rats and frogs. % 1 1 1 [Turn over Page 14 MARKS DO NOT WRITE IN THIS MARGIN 6. The diagram shows genetically modified yeast growing in a fermenter in a medium to which the amino acid lysine has been added. air in stirrer filter genetically modified yeast + growth medium + lysine (a) (i) Name the process for which the yeast cells need the amino acid lysine. (ii) The fermenter contains 5·5 litres of growth medium. Calculate the mass of lysine which should be added to the medium to give a concentration of 300 mg/l. Space for calculation mg (iii) The air entering the fermenter passes through a filter to prevent contamination. Explain why it is necessary to prevent contamination of the culture. 1 1 1 Page 15 MARKS DO NOT WRITE IN THIS MARGIN 6. (a) (continued) (iv) The optimum pH for yeast growth is 4·5. Suggest how this pH could be maintained in the fermenter. (b) Some phases of a growth curve of yeast culture are shown. A B Time Yeast cell number Complete the table by selecting growth phase A or B. Name the chosen phase and describe an event which occurs during that phase of growth. Letter Phase of growth Description (c) Describe a safety mechanism used to prevent the survival of genetically modified microorganisms in the external environment. [Turn over 1 2 1 Page 16 MARKS DO NOT WRITE IN THIS MARGIN 7. Sea bass are saltwater fish that can regulate their internal salt concentration. They have specialised cells in their gills with protein pumps in the membrane. These pumps actively transport excess salt from their bodies. (a) The specialised cells have many mitochondria. Explain why this is necessary. (b) Many animal species regulate their body temperature. Explain the importance of regulating body temperature. (c) Compare regulators and conformers in terms of their ecological niches. 2 1 1 Page 17 [Turn over for next question DO NOT WRITE ON THIS PAGE Page 18 MARKS DO NOT WRITE IN THIS MARGIN 8. Deer mice (Peromyscus maniculatus) are small mammals living in a variety of habitats ranging from low to high altitude. An investigation was carried out to compare the haemoglobin from two populations of deer mice living at low and high altitudes. Blood samples were taken from both populations and exposed to different levels of oxygen. The percentage of haemoglobin in the blood samples which had oxygen bound to it was measured. The results are shown in the graph. 120 100 80 60 40 20 100 90 80 70 60 50 40 30 20 10 0 Oxygen level to which blood sample was exposed (units) Haemoglobin with bound oxygen (%) haemoglobin from deer mice living at high altitude haemoglobin from deer mice living at low altitude Key (a) (i) State one variable that should be controlled when exposing the blood samples to oxygen in order for a valid conclusion to be drawn. 1 Page 19 MARKS DO NOT WRITE IN THIS MARGIN 8. (a) (continued) (ii) State the oxygen level at which there is the greatest difference in the percentage of haemoglobin bound to oxygen between the two groups. units (iii) Use information from the graph to explain how the deer mice from the population living at high altitude are adapted to a low oxygen niche. (b) Suggest one physiological adaptation, other than differences in haemoglobin, that deer mice from high altitudes could have to increase the efficiency of oxygen delivery to cells. (c) Describe the structure of a deer mouse heart and explain how this allows efficient delivery of oxygen to cells. Description Explanation [Turn over 1 1 1 2 Page 20 MARKS DO NOT WRITE IN THIS MARGIN 9. Catalase is an enzyme which breaks down hydrogen peroxide into oxygen and water. Paper discs soaked in catalase sink when placed into hydrogen peroxide solution. The discs rise to the surface when oxygen is produced. The time taken for the discs to rise can be used to measure catalase activity. An experiment was set up to investigate the effect of copper sulfate concentration on catalase activity. Six tubes were set up, each containing 10 cm3 of hydrogen peroxide and 5 cm3 of a different concentration of copper sulfate. One paper disc was then placed into each test tube as shown in the diagram. The time taken for each paper disc to rise to the surface was recorded. hydrogen peroxide (10 cm3) + copper sulfate (5 cm3) Paper disc The results are shown in the table. Concentration of copper sulfate solution (mol l−1) Time taken for paper disc to rise (seconds) 0·2 8 0·3 12 0·4 15 0·6 18 0·8 19 1·0 20 (a) (i) Name the independent variable in this experiment. (ii) Describe a suitable control for this experiment. (iii) Suggest how the temperature of the tubes could be kept constant. 1 1 1 Page 21 MARKS DO NOT WRITE IN THIS MARGIN 9. (a) (continued) (iv) Give a feature of the experiment which may make the results unreliable. (b) (i) Draw a line graph using the results in the table. (Additional graph paper, if required, will be found on Page 32.) (ii) Calculate the percentage increase in the time taken for the paper disc to rise when the copper sulfate concentration increased from 0·2 mol l−1 to 1·0 mol l−1. Space for calculation % (c) Draw a conclusion from the results of this experiment. 1 2 1 1 [Turn over Page 22 MARKS DO NOT WRITE IN THIS MARGIN 10. Answer either A or B in the space below. A Write notes on primate behaviour. OR B Write notes on invasive species. 4 4 Page 23 MARKS DO NOT WRITE IN THIS MARGIN 11. During photosynthesis light energy is absorbed by photosynthetic pigments in the chloroplasts. (a) (i) State one fate of the light which is not absorbed by the photosynthetic pigments. (ii) Describe the effect of absorbed light energy on the pigment molecules. (iii) Plants contain several pigments including chlorophyll a, chlorophyll b and carotenoids. Explain the advantage to a plant of having more than one type of photosynthetic pigment. (b) Following photolysis, hydrogen is transferred to the coenzyme NADP. State the source of this hydrogen. (c) Describe the role of the NADPH in the Calvin cycle (carbon fixation). [Turn over 1 1 1 1 1 Page 24 MARKS DO NOT WRITE IN THIS MARGIN 12. Potato plants are attacked by leaf eating caterpillars. Bacillus thuringiensis is a bacterium which can be used to control these pests. The bacteria produce a protein (Bt toxin) which kills these caterpillars. (a) (i) Explain how an attack by leaf eating caterpillars causes a reduction in crop yield. (ii) State an advantage of using this type of biological control rather than using chemicals. (b) Bt toxin does not kill all caterpillars. A study was carried out to investigate the effectiveness of the Bt toxin compared with a modified Bt toxin by exposing different groups of caterpillars to them. The results are shown in the table. Number of caterpillars tested Number of caterpillars surviving Caterpillars killed (%) Toxin tested Bt toxin alone 240 204 Modified Bt toxin alone 300 105 65 Bt toxin and modified Bt toxin used together 210 42 80 (i) Complete the table to show the percentage of caterpillars killed by the Bt toxin alone. Space for calculation 2 1 1 Page 25 MARKS DO NOT WRITE IN THIS MARGIN 12. (b) (continued) (ii) The Bt toxin and modified Bt toxin work by different mechanisms. Use information from the table to justify this statement. [Turn over 1 Page 26 MARKS DO NOT WRITE IN THIS MARGIN 13. Gluten is a protein found in crops that can cause human health problems. Scientists are breeding barley cultivars to produce ultra low gluten levels. A commercially produced barley (Sloop) and a low gluten cultivar (LG) were crossed to produce two different cultivars with ultra low gluten levels (ULG 1 and ULG 2). The gluten content of each cultivar is shown in the table. Barley cultivar Gluten content (mg/g) Sloop 57·0 LG 5·1 ULG 1 1·7 ULG 2 0·004 (a) Calculate how many times greater the gluten content of Sloop is compared to that of ULG 2. Space for calculation times greater (b) The allele for ultra low gluten is recessive. To investigate if the cultivar LG was heterozygous for gluten, it was crossed with the cultivar ULG1 which was homozygous for this recessive allele. offspring ULG1 low gluten cultivar × (i) Name this type of cross. (ii) Describe the expected phenotypes of the offspring if LG was heterozygous. 1 1 1 Page 27 MARKS DO NOT WRITE IN THIS MARGIN 13. (continued) (c) Barley is a naturally inbreeding plant. Explain why inbreeding depression would be unlikely to be a problem when a barley cultivar self-pollinates for many generations. (d) Barley grains contain the enzyme amylase which breaks down starch in the grain to sugar used in brewing beer. Average grain mass, starch content and amylase activity for three barley cultivars are shown in the table. Average mass of a single grain (mg) Starch content of grains (%) Amylase activity (units/mg ) Barley cultivar Sloop 53·6 70 0·6 ULG1 33·5 65 1·0 ULG2 39·2 64 1·4 (i) As well as total mass of all the grains, state the information required in order to calculate the average mass of a single grain. (ii) Select a cultivar from the table that would be best to use in beer production and justify your selection. Cultivar Justification [Turn over 1 1 1 Page 28 MARKS DO NOT WRITE IN THIS MARGIN 14. African wild dogs are carnivores which live in packs and use cooperative hunting. Each wild dog requires an average of 30 000 kJ of energy per day for the pack to survive. The bar chart shows the relationship between pack size and energy gain per wild dog per day. 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 50 000 40 000 30 000 20 000 10 000 0 Pack size (number of wild dogs) Energy gain (kJ/wild dog/day) (a) Using information from the bar chart, state the minimum pack size (i) at which cooperative hunting becomes an advantage; wild dogs (ii) for survival of the pack. wild dogs (b) Suggest why wild dogs in larger packs gain more energy per individual from hunting even though there are more animals to be fed. (c) Most of the wild dogs in a pack are related. Usually only one dominant female has offspring which other members of the pack will feed. Explain why pack members feed offspring which are not their own. 1 1 1 1 Page 29 MARKS DO NOT WRITE IN THIS MARGIN 15. Answer either A or B in the space below and on Pages 30 and 31. A Write notes on the citric acid cycle of cell respiration. OR B Write notes on how animals survive and avoid adverse conditions. 7 7 [Turn over Page 30 MARKS DO NOT WRITE IN THIS MARGIN SPACE FOR ANSWERS Page 31 MARKS DO NOT WRITE IN THIS MARGIN SPACE FOR ANSWERS [END OF QUESTION PAPER] Page 32 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK ADDITIONAL GRAPH PAPER FOR QUESTION 9 (b) (i) Page 33 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK Page 34 MARKS DO NOT WRITE IN THIS MARGIN ADDITIONAL SPACE FOR ANSWERS AND ROUGH WORK Page 35 [BLANK PAGE] DO NOT WRITE ON THIS PAGE Page 36 [BLANK PAGE] DO NOT WRITE ON THIS PAGE