aqa-a-level-biology-paper-2-2020-queston-paper-verified-quest

1 The iris in the human eye is a muscular structure. The iris changes the size of the pupil. Figure 1 shows the muscles in the iris. Figure 1 . Suggest and explain how the interaction between the muscles labelled in Figure 1 could cause the pupil to constrict (narrow). [2 marks] 0 1 Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 3 Do not write outside the *03* IB/M/Jun20/7402/2 2 3 . The fovea of the eye of an eagle has a high density of cones. An eagle focuses the image of its prey onto the fovea. Explain how the fovea enables an eagle to see its prey in detail. box Do not refer to colour vision in your answer. [3 marks] . The retina of the human eye has an area of approximately 1.094 × 10 3 mm2 The circular fovea in a human eye has a diameter of 3 × 10 3 µm Calculate the area of the fovea as a percentage of the area of the retina. The area of a circle is πr 2 . Use π = 3.14 in your calculation. Show your working. [2 marks] Answer % Question 1 continues on the next page Turn over ► 0 1 0 1 Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 4 Do not write outside the *04* IB/M/Jun20/7402/2 4 10 . The retina of an owl has a high density of rod cells. Explain how this enables an owl to hunt its prey at night. Do not refer to rhodopsin in your answer. [3 marks] box 0 1 Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 5 Do not write outside the *05* IB/M/Jun20/7402/2 1 2 Testosterone is a steroid hormone that belongs to a group of male sex hormones called androgens. box . Steroid hormones are hydrophobic. Explain why steroid hormones can rapidly enter a cell by passing through its cell-surface membrane. [2 marks] . In the cytoplasm, testosterone binds to a specific androgen receptor (AR). An AR is a protein. Suggest and explain why testosterone binds to a specific AR. [2 marks] Question 2 continues on the next page Turn over ► 0 2 0 2 0 2 Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 6 Do not write outside the *06* IB/M/Jun20/7402/2 3 4 9 . The binding of testosterone to an AR changes the shape of the AR. This AR molecule now enters the nucleus and stimulates gene expression. Suggest how the AR could stimulate gene expression. box [2 marks] The gene that codes for the AR has a variable number of CAG repeats. Some studies have shown an association between the number of CAG repeats and the risk of developing prostate cancer. Table 1 shows the results of a statistical test from one study. Table 1 Number of CAG repeats in the AR gene Probability (P) value ⩽ 16 0.02 ⩽ 17 0.30 ⩽ 18 0.07 ⩽ 19 0.09 ⩾ 20 0.06 . What can you conclude from the data in Table 1? [3 marks] 0 2 0 2 Downloaded by: ibrahim03naqvi | Distribution of this document is illegal S - The Marketplace for Revision Notes & Study Guides 7 Do not write outside the IB/M/Jun20/7402/2 Question 3 continues on the next page box *07* Turn over ► 0 3 Figure 2 shows one type of calorimeter. Figure 2 A calorimeter can be used to determine the chemical energy store of biomass. A known mass of biomass is fully combusted in a calorimeter. The heat energy released from this combustion increases the temperature of the water in the calorimeter. The increase in the temperature of a known volume of water is recorded