AQA A Level Biology Paper 1: 2018 Exam Questions and Answers, Exams of Advanced Education

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2018 Paper 1 (A Level) , AQA

Biology

What is meant by 'species richness'? (1) - 1. A measure if the number of different species in a community From the data in Figure 4, a student made the following conclusions.

1. The natural habitat is most favourable for bees.
2. The town is the least favourable for bees. Do the data in Figure 4 support these conclusions? Explain your answer. (4) - The natural habitat is most favourable for bees
3. Peak of mean bee numbers in natural habitat is highest
4. The mean number of bees was higher in the natural habitat until day 200
5. Mean species richness highest at all times The town is the least favourable for bees
6. Mean species richness is lower in farmland until day 125
7. Similar mean number of bees to farmland The scientists collected bees using a method that was ethical and allowed them to identify accurately the species to which each belonged. In each case, suggest one consideration the scientists had taken into account to make sure their method (2) - was ethical
8. Must not harm bees OR Must allow the bee to be release unchanged Allowed them to identify accurately the species to which reach belonged
9. Must allow close examination
10. Use a key/photo evidence to identify species

Suggest and explain two ways in which the scientists could have improved the method used for data collection in this investigation. (2) - 1. Collect at more times of the year so more points on graph/line of best fit on graph

2. Counted number of individuals in each species so that they could calculate index of diversity
3. Collected from more area/sites to increase accuracy of mean data Formation of an enzyme-substrate complex increases the rate of reaction. Explain how. (2) - 1. Reduces activation energy
4. Due to bending bonds
5. Without enzymes, substrates don't have sufficient energy for reaction released per second. Without the enzyme, 3.0 × 10 amino acids were released per second. Calculate by how many times the rate of reaction is greater with the enzyme present. Give your answer in standard form. (2) - 1. 1.93 x 10 (-9) times faster
6. 1 mark for; 578/3.0x10(-9) Calculate the rate of reaction of the enzyme activity with no lyxose at 2.5 mmol dm−3 of ATP as a percentage of the maximum rate shown with lyxose. (2) - 1. 31.4%
7. 1 mark for; 0.44 and 1.4/32.8/33.1/30/29/ Lyxose binds to the enzyme. Suggest a reason for the difference in the results shown in Figure 5 with and withoutlyxose. (3) - 1. Binding alters the tertiary structure of the enzyme
8. This causes active site to change shape
9. More successful ES complexes form
10. ES complexes form more quickly Explain how the treatment with antivenom works and why it is essential to use passive immunity, rather than active immunity. (2) - 1. Antibodies bind to the toxin/venom/antigen and causes its destruction
11. Active immunity would be too slow

A mixture of venoms from several snakes of the same species is used. Suggest why. (2) - 1. May be different from of antigen/toxin

2. Different antibodies needed in the anti venom Horses or rabbits can be used to produce antivenoms. When taking blood to extract antibody, 13 cm3 of blood is collected per kg of the animal's body mass. The mean mass of the horses used is 350 kg and the mean mass of the rabbits used is 2 kg Using only this information, suggest which animal would be better for the production of antivenoms. Use a calculation to support your answer. (2) - 1. Horses because more antivenom/antibodies could be collected as more blood collected
3. 455o cm cubed v 26cm cubed blood collected During the procedure shown in Figure 8 the animals are under ongoing observation by a vet. Suggest one reason why. (1) - 1. So the animal doesn't suffer from the venom/vaccine/toxin
4. So animal doesn't suffer anaemia as a result of blood collection
5. So the animal does not have pathogen that could be transferred to human During vaccination, each animal is initially injected with a small volume of venom. Two weeks later, it is injected with a larger volume of venom. Use your knowledge of the humoral immune response to explain this vaccination programme. (3) - 1. B cell specific to the venom reproduce by mitosis
6. B cells produce plasma cell and memory cells
7. The second dose produces antibodies in secondary immune response in higher concentration and faster
8. First does must be small so animal isn't killed The scientists concluded that this heat treatment damaged the phloem. Explain how the results in Figure 9 support this conclusion. (2) - 1. Radioactively labelled carbon converted into sugars/organic substances during photosynthesis

2. Mass flow/translocation in phloem only in untreated plants OR
3. Phloem requires living cells/respiration
4. Heat treatment damages living cells so transport in the phloem throughout plant only in untreated plants The scientists also concluded that this heat treatment did not affect the xylem. Explain how the results in Table 4 support this conclusion. (2) - 1.water content was not significantly different because standards deviations overlap
5. Water therefore still being transported in xylem to the leaf
6. Movement in xylem is passive so unaffected by heat treatment What can you conclude about the movement of Fe3+ in barley plants? Use all the information provided. (4) - 1. Heat treatment has greater effect on young leaves than old leaves
7. Heat treatment damages phloem
8. Fe3+ moves up the leaf/plant
9. Fe3+ transported in the xylem in the older leaf
10. Higher ratio of Fe3+ in old leaves than young
11. All ratios show there is less Fe3+ in the top than the lower part of the leaves
12. No stats test so show if difference is significant Describe the gross structure of the human gas exchange system and how we breathe in and out. (6) - 1. Named structure; trachea, bronchi, bronchioles then alveoli
13. Correct order
14. Breathing in - diaphragm contracts and external intercostal muscles contract
15. Causes volume increase in thorax and pressure decrease in thoracic cavity below atmospheric pressure to air flows in
16. Breathing out - diaphragm relaxes and internal intercostal muscles contract

6. Volume decrease in thorax and pressure increase in thoracic cavity above atmospheric to air flows out Mucus produced by epithelial cells in the human gas exchange system contains triglycerides and phospholipids. Compare and contrast the structure and properties of triglycerides and phospholipids. (5) - 1. Both contain an ester bond between glycerol and fatty acids
7. Both contain glycerol
8. Fatty acids on both may be saturated or unsaturated
9. Both are insoluble in water
10. Both contain C, H and O but phospholipids also contain P
11. Triglyceride has 3 fatty acids and phospholipids have 2 fatty acids plus phosphate group 7 triglycerides are non polar, phospholipids have hydrophilic and hydrophobic regions
12. Phospholipids form bilateral but triglycerides don't Mucus also contains glycoproteins. One of these glycoproteins is a polypeptide with the sugar, lactose, attached. Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein. (4) - 1. Glucose and galactose
13. Joined by condensation reaction
14. By glycosidic bond
15. Added to polypeptide in Golgi apparatus