2015 GCE O Level Bio Suggested Answer JEN (FPE Edited)

2015 GCE O Level Biology Suggested Answer Paper 1 1 2 3 4 5 6 7 8 9 10 B C B B B B D B D C 11 12 13 14 15 16 17 18 19 20 B C C B B A D C C C 21 22 23 24 25 26 27 28 29 30 B D B A D A C B A D 31 32 33 34 35 36 37 38 39 40 C B B A A D A A A B Paper 2 (Section A) 1 (a) A: starch [1] B: maltose [1] C: salivary amylase [1] (b) (i) Temperature [1] (ii) pH [1] (c) When gallstones block the bile duct, bile cannot be secreted from the gall bladder into the duodenum [1]. This prevents the emulsification of fats and there is reduced surface area to volume ratio available for digestion of fats by lipases [1]. This would slow down the digestion of fats in fatty acid and glycerol [1]. 2 (a) Sexual reproduction is a process involving the fusion of a male and female haploid gamete to form a diploid zygote [1]. Meiosis is involved in the production of haploid gametes [1]. Sexual reproduction produces genetically dissimilar offspring [1]. (b) The pollen are large with spiky, rough surfaces [1] so that they can readily cling onto the body of insects [1]. (c) (i) A: pollen tube [1] Questions to note: Question to note: 1a, 3, 5a, 5b, 6bii, 8bii, 9, 10, 11O

(ii) The pollen tube secretes enzymes that will digest the tissue in the style and allow the pollen tube to grow through the style and into the ovary [1]. It enters the ovule through the micropyle [1]. Within the ovule, the tip of the pollen tube absorbs sap and bursts, releasing two male gametes into the ovule [1]. 3 (a) 24 °C (b) 1. As air temperature increases, the body temperature of the insect also increases [1]. 2. The insect was not able to maintain a constant internal body temperature through homeostasis [1]. (c) 1m – constant temperature of 36.5 °C to 37.4 °C 1m – not extrapolation; graph spans only between air temperatures of 20 °C and 36 °C. (d) When body temperature increases beyond the set point, thermoreceptors detect the increase and stimulate the sweat glands to become more active [1]. More sweat is being produced and when sweat evaporates from the skin, more heat is loss as latent heat of vaporisation [1], hence cooling the body and bringing down body temperature back to the normal set point [1]. 4 (a) A: aorta [1] B:pulmonary vein [1] (b) The semi-lunar valves prevent the backflow of blood from the pulmonary artery into the right ventricle [1], ensuring blood only travels in one direction. (c) Deoxygenated blood is returned to the right atrium from the body organs via the vena cava [1]. The muscles of the right atrium contract during atrial systole. When pressure in the right atrium is higher than right ventricle, tricuspid valves open and blood is forced into the right ventricle [1]. The muscles of the right ventricle then contract during ventricular systole, pushing open the semi-lunar valves and forcing blood out of the heart into the pulmonary artery