ACSI P2 MS - Y4 Exp Bio Prelim 2024

2024 YEAR 4 EXPRESS BIOLOGY PRELIMINARY EXAMINATION PAPER 2 MARK SCHEME Section A 1a) right ventricle; 1b) increases when heart / ventricle + contracts/systole; decreases when heart / ventricle + relaxes/diastole; 1ci) lung; 1cii) Oxygen diffuse from the air spaces in the alveoli/lung to the blood capillaries; Carbon dioxide diffuse from the blood into the air spaces in the alveoli/lung; 1d) clusters of alveoli -> increase SA:V single cell epithelium/ thin wall -> reduce distance travelled constant blood flow -> maintain concentration gradient (any 2 pairs) Reject: Moist surface-> allow gases to dissolve (does not increase efficiency) 2a) Percentage difference in mean fresh mass = (98.0-86.5/86.5)x100%=13(whole number) 2b) Increase in height → more sunlight can be absorbed; allow more room for corn to form/grow; Increased number of leaves → increases the surface area exposed to sunlight; increases the amount of gaseous exchange; increases amount of chloroplast/chlorophyll; (any 3) leading to increases the yield of corn; 2c) Reject: Light intensity/Temperature/Carbon dioxide concentration/humidity (all these factors will change in the glass house) Accept: amount of water, type of corn seeds, space between corn plant, type of soil, nutrients/fertilizer level, number of plants for experiment 2d) Light intensity: lights can be installed to provide light to the plants under low light conditions (e.g. at night, early morning); Temperature: heater may be installed to provide sufficient heat for enzymes to function close to their optimum temperature for photosynthesis; Carbon dioxide: Any valid method to increase carbon dioxide levels. E.g. burning of candles, rearing of pets / livestock in glasshouse; 3a) correct label on the diagram 3b) hotter/warmer/higher temperature;

3c) Sweat glands more active/more sweat secreted; More latent heat (of vapourisation) removed from body due to evaporation of water in the sweat; Skin arteriole dilated; more blood reaches the skin arterioles, resulting in more heat lost through the surface of the skin via through convection, radiation and conduction; 3di) ADH increased 3dii) Walls of the collecting duct more permeable to water, more water selectively reabsorbed via osmosis from the lumen of the collecting duct back into blood; Lesser volume and more concentrated urine produced; 4ai) aa; 4aii) A and a OR A and a. Reject a and a, AA, Aa 4b) *Correct shading required 4c) State one type of chemical, e.g. tar; radiation, e.g. ultraviolet radiation 4d) closely related people possess similar genotype Higher chance of homozygous genotype Recessive condition will be expressed 5a) the process involving the fusion of nuclei of male and female gametes to form a zygote; and the production of genetically dissimilar/ different/ non-identical offspring; 5bi) menstruation 5bii) pregn