SJI_2020 Y3 EOY Biology 6093 student answers

St Joseph’s Institution END-OF-YEAR Examination 2020 Year 3 Biology OP Page 1 of 12 Marking Scheme SUBJECT: BIOLOGY EXAMINATION: END-OF-YEAR LEVEL: YEAR 3 OP Paper 1 Paper 2 Section A: QN NO. SUGGESTED ANSWER SCHEME (PAPER 2 SECTION A) 1ai) Gland cell ii) To secrete mucus to trap dust particles and micro-organisms. bi) Increase in volume will lead to decrease in pressure of thoracic cavity. Inversely proportional ii) Internal intercostal muscle contracts, external intercostal muscle relaxes; Ribcage and sternum moves downwards and inwards; Diaphragm relaxes and arches upwards; This leads to decrease in thoracic cavity volume and increase in pressure of thoracic cavity; Pressure in the thoracic cavity is higher than the surrounding and air leaves the lungs; c) Carbon monoxide binds permanently with haemoglobin to from carboxyl haemoglobin; 1 C 9 A 17 C 25 A 2 B 10 D 18 C 26 B 3 B 11 D 19 A 27 D 4 A 12 C 20 D 28 A 5 B 13 A 21 C 29 A 6 D 14 B 22 D 30 D 7 C 15 A 23 A 8 A 16 D 24 A

St Joseph’s Institution END-OF-YEAR Examination 2020 Year 3 Biology OP Page 2 of 12 QN NO. SUGGESTED ANSWER SCHEME (PAPER 2 SECTION A) This results in lesser oxygen being transported in the body; Lower rate of aerobic respiration, less energy released+ person will feel fatigued; Increase fatty deposits on the arteries; Lesser oxygen supplied to heart muscles+ lower rate of aerobic respiration+ higher chance of coronary heart disease 2a 0.3s 0.1-0.4s b) During ventricular systole, ventricle walls contract. Pressure in the ventricles is higher than the atria+ This increase in pressure in the ventricles causes the bicuspid and tricuspid valves to close to prevent backflow of blood into the atria. This produces a ‘lub’ sound. During ventricular diastole, the ventricle walls relax. Pressure in the ventricles is lower than the atria+ The lowered pressure in the ventricles causes the semilunar valves to close. This produces a ‘dub’ sound. ci) 138-64/64X100%=116% ii) Increase in heartbeat+ Increase in breathing rate; (no explanation) Increase in muscular contractions during the exercise + requires large amount of energy Increase rate of aerobic respiration to meet the increase in energy demand; Increase in heartbeat to supply blood containing oxygen and glucose at a faster rate +to muscle tissues; Increase in breathing rate to supply oxygen for aerobic respiration and to remove carbon dioxide produced; iii) Produced during anaerobic respiration in muscle cells, when insufficient oxygen is available for aerobic respiration. Accumulation of lactic acid in muscles may cause fatigue, muscular pains and cramps.

St Joseph’s Institution END-OF-YEAR Examination 2020 Year 3 Biology OP Page 3 of 12 QN NO. SUGGESTED ANSWER SCHEME (PAPER 2 SECTION A) 3a capillary, Any two from: blood cells move in Vessel B in single file AW / running between body cells / walls are