CCHY 2012 Bio Yearly TYS ANS

6093 Biology Yearly TYS 2012 No Paper 1 Marks Remarks 1 B 1 2 C 1 3 D 1 4 D 1 5 A 1 6 A 1 7 C 1 8 B 1 9 C 1 10 D 1 11 C 1 12 C 1 13 B 1 14 C 1 15 D 1 16 B 1 17 C 1 18 D 1 19 D 1 20 C 1 21 C 1 22 B 1 23 A 1 24 A 1 25 D 1 26 C 1 27 C 1 28 A 1 29 B 1 30 C 1 31 A 1 32 D 1 33 A 1 34 B 1 35 A 1 36 C 1 37 C 1 38 B 1 39 D 1 40 B 1 Total 40

Paper 2 Section A 1a Gene is a unit of inheritance, born on a particular locus of a chromosome; gene is a small segment of DNA in a chromosome, made up of a sequence of nucleotides that codes for the production of polypeptides; 1 1 1bi Both parents are Aa. 1 1bii 3:1 1 1biii AA, Aa 1 Total 5 2a Larger sample size to increase accuracy of results + offset any anomaly in readings 1 2b amount of urea increased almost 4 times when amount of protein increases from low protein level at 4.75g of urea per day to normal protein level at 19.2g of urea per day; amount of urea increased almost 6 times when amount of protein increases from low protein level at 4.75g of urea per day to high protein level at 31.5g of urea per day; 1 1 Compare low and normal Compare low and high 2ci Protein At glomerulus, proteins are retained in the glomerular capillaries; they are too large to pass through the walls of the glomerular capillaries and the partially permeable basement membrane; Glucose High hydrostatic blood pressure in glomerulus forces glucose out of glomerulus into Bowman’s capsule by ultrafiltration; At PCT, most glucose are selectively reabsorbed through the walls of the tubule into the surrounding blood capillaries by diffusion and active transport + glucose are required by the body + reabsorbed readily; 1 1 1 1 2cii 0.015 ÷ 0.01 = x1.5 1 Total 8

3ai A: hair B: blood capillary D: adipose tissue 1 1 1 3aii body temperature is higher than normal level detected by the thermoreceptors, stimulates hypothalamus which in turn stimulates sweat glands to become more active; Increased production of sweat + more water in sweat evaporates into water vapour from skin surface; More latent heat of vaporisation is lost from body + lose heat + temperature is restored to normal level; 1 1 1 Stimulus + gland + effect 3bi 37.1 – 36.72 = 0.38 1 3bii Decreased metabolic rate; reduce the amount of heat released; / Sweat glands are more active; results in more sweat produced, more water in sweat evaporates into water vapour, more latent heat of vaporisation lost; / Dilation of arterioles; allow more blood flow + more heat loss by radiation, convection, conduction; 1 1 Total 9 4ai Carbon dioxide + water glucose + oxygen 1 R: no conditions, sunlight 4aii chloroplasts 1 4aiii Palisade mesophyll cell 1 R: layer 4bi stomata 1 R stoma 4bii Open in presence