page 14 19. Some processes involved in evolution are shown. 1 sexual selection 2 disruptive selection 3 genetic drift Which of these processes involve non-random changes in the frequency of DNA sequences? A 1 and 2 only B 1 and 3 only C 2 and 3 only D 1, 2 and 3 20. The analysis of DNA sequences from different organisms is used in the production of molecular clocks. This analysis is based on the assumption that over time DNA sequences undergo mutations A randomly B spontaneously C at a varying rate D at a constant rate. [END OF SECTION 1. NOW ATTEMPT THE QUESTIONS IN SECTION 2 OF YOUR QUESTION AND ANSWER BOOKLET.] page 15 [BLANK PAGE] DO NOT WRITE ON THIS PAGE page 16 [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 2018 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 11 and 14 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. X707/76/01 TUESDAY, 15 MAY 9:00 AM – 11:30 AM A/PB 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 Questions 11 and 14 contain a choice 1. The diagram illustrates thermoregulation in mammals following a decrease in body temperature. (a) (i) Name the type of control used in thermoregulation as shown in the diagram. (ii) Name the part of the brain in which thermoreceptors are found. (iii) State how information travels to the effectors in the skin. 1 1 1 thermoreceptors in the brain decrease in body temperature information travels to effectors in the skin corrective mechanism normal body temperature page 07 MARKS DO NOT WRITE IN THIS MARGIN 1. (continued) (b) Effectors in the skin include muscles in the walls of blood vessels. (i) Describe the response of these effectors to a decrease in body temperature. (ii) Explain how this response would help return body temperature to normal. (c) Explain why it is important for a mammal to regulate its body temperature. [Turn over 1 1 1 page 08 MARKS DO NOT WRITE IN THIS MARGIN 2. Daphnia (Daphnia pulex) is a species of water flea that lives in fresh water. An investigation was carried out into the effect of water temperature on the heart rate of one Daphnia. The results are shown in the table. Water temperature (°C) Heart rate (beats per minute) 2 175 7 184 12 194 17 207 22 219 (a) Calculate the average increase in heart rate per °C between 2 °C and 22 °C. Space for calculation beats per minute per °C (b) Daphnia is a conformer. Use evidence from the table to confirm this statement. (c) Explain how an increased water temperature would result in a higher metabolic rate in Daphnia. (d) State the type of response shown by conformers to maintain an optimum metabolic rate. 1 1 2 1 page 09 [Turn over for next question DO NOT WRITE ON THIS PAGE page 10 MARKS DO NOT WRITE IN THIS MARGIN 3. The bacteria Streptomyces is a microorganism found in soil. It produces a secondary metabolite, the antibiotic streptomycin, which kills other microorganisms. Streptomyces live in close association with plant roots. These plants produce soluble carbohydrates which are released into the soil through their roots. (a) (i) Name the growth phase during which streptomycin is produced. (ii) Explain the advantage to Streptomyces of producing an antibiotic such as streptomycin. (b) The relationship between Streptomyces and the plant roots is described as mutualistic. (i) Suggest the benefit to Streptomyces. (ii) Suggest the benefit to the plant. 1 1 1 1 page 11 MARKS DO NOT WRITE IN THIS MARGIN 3. (continued) (c) An investigation was set up to compare the effectiveness of streptomycin with other antibiotics by measuring the survival of bacteria. A species of bacteria was grown in the presence of different concentrations of antibiotics and the percentage which survived was calculated. The results are shown in the table. Antibiotic Concentration of antibiotic (µg/cm3) Survival of bacteria (%) Fusidic acid 10 6 Chloramphenicol 25 42 Erythromycin 5 49 Gentamycin 10 5 Tetracycline 25 35 Streptomycin 10 35 (i) Name one antibiotic with which streptomycin could be validly compared. (ii) Give a conclusion which can be drawn from the results. [Turn over 1 1 page 12 MARKS DO NOT WRITE IN THIS MARGIN 4. The diagram shows information on the breeding and migration of Monarch butterflies (Danaus plexippus). Each generation dies after laying eggs. (a) State one advantage and one disadvantage to the Monarch butterfly of migration to Mexico. Advantage Disadvantage 2 4th generation migrate to North America in the spring and breed to produce a new 1st generation 1st generation breed and produce the 2nd generation in early summer in North America 2nd generation breed and produce the 3rd generation in late summer in North America 4th generation migrate south to Mexico for the winter 3rd generation breed and produce the 4th generation in autumn in North America page 13 MARKS DO NOT WRITE IN THIS MARGIN 4. (continued) (b) The migratory behaviour of the Monarch butterfly from North America to Mexico is innate. Use the information given to justify this statement. (c) Some species of hummingbird also migrate between North America and Mexico. They have high metabolic rates which they reduce while resting each night during the migration period. Name this reduction in metabolic rate. [Turn over 1 1