AQA 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 2 *02* IB/M/Jun22/7402/2 Do not write ou ...

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/Jun22/7402/2 Do not write outside the Answer all questions in the spaces provided. box 0 1 . 1 In the following passage the numbered spaces can be filled with biological terms. During photosynthesis, plants produce (1) compounds which contain carbon, such as carbohydrates, lipids and proteins. Most of the sugars synthesised by plants are used by the plant in (2) . The rest are used to make other groups of biological molecules. These biological molecules form the biomass of the plants. Biomass can be measured in terms of mass of (3) per given area per given time. The chemical energy store in dry biomass can be estimated using (4) . Write the correct biological term beside each number below, that matches the space in the passage. [2 marks] (1) (2) (3) (4) 3 *03* Turn over ► IB/M/Jun22/7402/2 Do not write outside the box 0 1 . 2 Describe the light-independent reaction of photosynthesis. [6 marks] 8 4 *04* IB/M/Jun22/7402/2 Do not write outside the box 0 2 . 1 Put a tick ( ) in the box next to the equation that shows how the net production of consumers, N, can be calculated where I represents the chemical energy store in ingested food F represents the chemical energy lost to the environment in faeces and urine R represents the respiratory losses to the environment. [1 mark] N = (I – F) + R N = I – (F + R) N = I + (F + R) N = I – (F – R) In the UK, some female cattle are only used for breeding. This female breeding herd has dairy cows and beef cows. Table 1 shows data on dairy cows and beef cows in the UK female breeding herd in December 2013 and December 2017. Table 1 Date Total number in female breeding herd / millions Percentage of total female breeding herd Dairy cows Beef cows December 2013 3.35 54 46 December 2017 3.45 55 45 5 *05* Turn over ► IB/M/Jun22/7402/2 Do not write outside the box 0 2 . 2 In December 2017, the female breeding herd was 48% of all female cattle in the UK. Use Table 1 to calculate the percentage of all female cattle that were beef cows in the UK in December 2017. [1 mark] Answer % 0 2 . 3 Use Table 1 to calculate the increase in the number of dairy cows in the UK female breeding herd between December 2013 and December 2017. Show your working. [2 marks] Increase in number 0 2 . 4 Farming cattle for humans to eat is less efficient than farming crops because of energy transfer. Explain why. [2 marks] 6 6 *06* IB/M/Jun22/7402/2 Do not write outside the box 0 3 Nitrogen-fixing bacteria such as Azotobacter chroococcum use the enzyme nitrogenase to produce ammonia from nitrogen gas in the air. A. chroococcum can use ammonium chloride as a direct source of ammonia. When a source of ammonia is not available this bacterium uses nitrogen fixation. A scientist investigated the effect of an increase in the concentration of ammonium chloride on the activity of nitrogenase in this bacterium. He prepared several liquid medium cultures of the bacterium. Each liquid culture had the same volume. He grew each culture in a different concentration of ammonium chloride. In each culture: • he recorded the nitrogenase activity in arbitrary units • he removed the bacteria and then recorded the concentration of ammonium chloride remaining in each liquid medium. Table 2 shows the scientist’s results. Table 2 Concentration of ammonium chloride / µg cm–3 Nitrogenase activity / arbitrary units Concentration of ammonium chloride remaining in liquid medium / µg cm–3 0 45 0 20 30 0 40 17 0 60 7 0 80 0 6 100 0 14 120 0 20 0 3 . 1 Apart from temperature and pH, give two variables the scientist would have controlled when preparing the liquid medium cultures. [2 marks] 1 2 7 *07* Turn over ► IB/M/Jun22/7402/2 Do not write outside the box 0 3 . 2 A student concluded that this investigation showed that ammonia inhibits nitrogenase activity in nitrogen-fixing bacteria. Use all the information to evaluate the student’s conclusion. [3 marks] 0 3 . 3 Nitrogenase catalyses the reduction of nitrogen during nitrogen fixation. The reaction requires 16 molecules of ATP for each molecule of nitrogen that is reduced. When ammonia inhibits nitrogenase activity, nitrogen-fixing bacteria may benefit. Explain how. [2 marks] 7 8 *08* IB/M/Jun22/7402/2 Do not write outside the box 0 4 . 1 Put a tick ( ) in the box next to the process that occurs in anaerobic respiration but does not occur in aerobic respiration. [1 mark] Phosphorylation of glucose Reduction of NAD Reduction of pyruvate Substrate-level phosphorylation A student used the apparatus shown in Figure 1 to measure the rate of aerobic respiration of seeds for 48 hours. Figure 1 9 *09* Turn over ► IB/M/Jun22/7402/2 Do not write outside the box 0 4 . 2 During the 48 hours, the coloured liquid moved to the left. Explain why. [3 marks] 0 4 . 3 Apart from time, give two measurements the student would have to make to determine the rate of aerobic respiration of these seeds in cm3 hour –1 [2 marks] 1 2 Question 4 continues on the next page 10 *10* IB/M/Jun22/7402/2 Do not write outside the box 0 4 . 4 The student used the same apparatus to determine the volume of carbon dioxide the seeds produced during 48 hours. Give the change the student would need to make to the contents of the apparatus and describe how he could calculate the volume of carbon dioxide produced. [3 marks] 0 4 . 5 The student calculated that during the 48 hours, 6.2 × 10–4 cm3 of oxygen was absorbed by 40 g of seeds. Calculate the oxygen uptake in cm3 g–1 hour –1 [1 mark] Answer cm3 g–1 hour –1 10 11 *11* Turn over ► IB/M/Jun22/7402/2 Do not write outside the Turn over for the next question box DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED 12 *12* IB/M/Jun22/7402/2 Do not write outside the box 0 5 Lemurs are small mammals. Lemurs live in trees and feed on leaves and fruit. Scientists used a computer program to predict the expected distribution of two species of lemur, Eulemur rufus and Eulemur rufifrons, on the island of Madagascar. These predictions were based on the environmental needs of each species. Then, the scientists determined the actual distribution of these two species of lemur on the island of Madagascar. Figure 2 shows the scientists’ results. Figure 2 13 *13* Turn over ► IB/M/Jun22/7402/2 Do not write outside the box 0 5 . 1 Using Figure 2, give three conclusions you can make about the distribution of these lemur species. [3 marks] 1 2 3 0 5 . 2 Using all the information, suggest how speciation happened to produce two species of lemur. [5 marks] Question 5 continues on the next page 14 *14* IB/M/Jun22/7402/2 Do not write outside the The scientists used the mark box -release-recapture method to determine the number of lemurs in one area of forest. They captured, marked and released a first sample of 30 lemurs. A week later, they captured a second sample of 25 lemurs from the same area of forest. The scientists calculated that there were 250 lemurs in that area of forest. 0 5 . 3 Suggest one precaution needed when marking the lemurs to make sure the estimate of the number of lemurs is valid. [1 mark] 0 5 . 4 Using the information provided, calculate how many lemurs in the second sample were marked. [1 mark] Answer 10 15 *15* Turn over ► IB/M/Jun22/7402/2 Do not write outside the Turn over for the next question box DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED 16 *16* IB/M/Jun22/7402/2 Do not write outside the box 0 6 In humans, the ABO blood groups and Rhesus blood groups are under genetic control. The inheritance of the ABO blood groups is controlled by three alleles of a single gene, I A, I B and I O. The alleles I A and I B are codominant, and the allele I O is recessive to I A and recessive to I B. There are four ABO phenotypes, A, B, AB and O. The gene for the Rhesus blood groups has two alleles. The allele for Rhesus positive, R, is dominant to the allele for Rhesus negative, r. The genes for the ABO and Rhesus blood groups are not sex-linked and are not on the same chromosome. Figure 3 shows the phenotypes in a family tree for the ABO and Rhesus blood groups. Figure 3 0 6 . 1 Give the genotypes of the ABO blood groups for individuals 1 and 2. Do not include the genotypes for the Rhesus blood groups in your answer. [1 mark] 1 2 17 *17* Turn over ► IB/M/Jun22/7402/2 Do not write outside the box 0 6 . 2 Explain one piece of evidence from Figure 3 that the allele for Rhesus positive is dominant. [2 marks] 0 6 . 3 Calculate the probability of individuals 1 and 2 producing a Rhesus positive son with blood group A (individual 3). You can assume that individual 1 is heterozygous for the Rhesus blood group. Show your working. [2 marks] Probability Scientists determined the frequencies of the ABO alleles and ABO phenotypes in a large population. They then used a statistical test to determine if the frequencies of the four phenotypes differed significantly from the frequencies expected according to the Hardy–Weinberg equation. 0 6 . 4 The frequencies of the I A and I O alleles were 0.15 and 0.65. What is the frequency of the I B allele? [1 mark] Frequency of I B allele 18 *18* IB/M/Jun22/7402/2 Do not write outside the box 0 6 . 5 Name the statistical test you should use to determine if the observed frequencies of the four phenotypes differed significantly from the frequencies expected according to the Hardy–Weinberg equation. State how many degrees of freedom should apply. [2 marks] Statistical test Number of degrees of freedom 0 6 . 6 The scientists concluded that the observed frequencies of the four phenotypes differed significantly from the expected frequencies. Use your knowledge of the Hardy–Weinberg principle to suggest two reasons why. [2 marks] 1 2 10 19 *19* Turn over ► IB/M/Jun22/7402/2 Do not write outside the box 0 7 . 1 Give two reasons why transmission across a choline