ACS(I) Y4 Pure Bio 2023 Y4 Exp Common Test - Answers

2023 YEAR 4 EXPRESS BIOLOGY COMMON TEST Section A: Multiple Choice Questions (30 marks) 1 D 11 B 21 C 2 A 12 C 22 D 3 C 13 A 23 B 4 C 14 A 24 A 5 A 15 A 25 C 6 B 16 D 26 B 7 B 17 B 27 D 8 C 18 B 28 B 9 A 19 D 29 B 10 A 20 C 30 D

Section B: Structured Questions (50 marks) 1 (a)(i) (ii) 1: pulmonary vein 2: semi-lunar valve/ pulmonary valve 3: right atrium Y (left ventricle) has thicker/ more muscular wall than the X (right ventricle) • more muscular force/contraction is required to generate a higher blood pressure • to push/ transport blood over a longer distance to the rest of the body organs / tissues / systemic circulation • there is also a greater resistance to blood flow to be overcome. [3] [3] (b)(i) (iii) coronary artery max. 3 • damaged tissues and platelets release thrombokinase • which in presence of calcium ions, converts prothrombin into active thrombin • thrombin converts soluble fibrinogen into insoluble fibrin • fibrin threads form mesh to trap red blood cells and platelets stick to fibrin mesh, forming clot [1] [3] [Total: 10] 2 (a)(i) (ii) (iii) • a chemical produced in small amounts by an endocrine gland • transported by blood (plasma) to the target organs where they alter the activity of target organ(s) • They are destroyed in the liver and excreted by the kidneys after they have carried out their functions. adrenaline hormone uptake of glucose by cells concentration of glucose in the blood insulin increases decreases glucagon decreases increases/stays in the same [3] [2] [1] (b) max. 4 • blood glucose concentration is kept constant/ within narrow limits (makes reference to homeostasis) • any deviation/ change from norm is detected/ acts as a stimulus • triggers corrective mechanism(s) • e.g. increased secretion of insulin to stimulate conversion of excess blood glucose to glycogen /ORA OR increased uptake of glucose by cells • to return concentrations/levels back to norm [4] [Total: 10] 3 (a)(i) (ii) 8% most amount of pollen grain germinated; longest length of pollen tube; [1] [2] (b)(i) (ii) wind pollinated; protruding/feathery stigma • pollen grain germinates in response to the sugary fluid secreted by the stigma • pollen tube grow out from the pollen grain and secretes enzymes to digest the surrounding tissue • travel down the stigma, style and ovary • enter through the micropyle • absorbs sap and burst, release the male gametes leading to fertilisation with the ovum [2] [5] [Total: 10]

4 (a)(i) (ii) X: oestrogen Y: progesterone Any of the correctly stated roles X (oestrogen) • to repair and stimulate the thickening of the endometrium/uterine lining after menstruation • very high concentration, it indirectly stimulates ovulation Y (progesterone) • main