TKGS 2024 S4 Prelim Bio P1 & P2 Answers

Tanjong Katong Girls’ School Secondary 4 Preliminary Examinations 2024 Answer Key Biology 6093/01 1 B 11 B 21 D 31 B 2 D 12 B 22 B 32 D 3 B 13 C 23 B 33 A 4 C 14 A 24 D 34 A 5 B 15 B 25 B 35 B 6 C 16 C 26 B 36 A 7 B 17 B 27 B 37 B 8 C 18 B 28 C 38 D 9 A 19 D 29 B 39 D 10 D 20 C 30 A 40 A Biology 6093/02 Question Answer Marks 1 (a) One-cell thick wall + decrease diffusion distance, increase rate of diffusion of gases; Close proximity to a blood capillary + decrease diffusion distance, increase rate of diffusion of gases; Max 1m (b) Microvilli; 1m (c) Lacteal; 1m (d) Oxygen; Glucose / amino acids / water / vitamins / minerals; 2m 2 (a) B is thicker, more elastic, more muscular than A; (vice versa) 1m (b) Arrows must show the following to get 1m: 1. right atrium to right ventricle 2. right ventricle to pulmonary artery 3. left atrium to left ventricle 4. left ventricle to aorta 1m (c) Tricuspid valve; Closes during ventricular systole + prevent blood from entering right atrium; 2m (d)(i) (60 / 0.8) = 75; 1m

(d)(ii) time / s at rest during exercise atrium ventricle atrium ventricle 0.0 – 0.1 0.1 – 0.2 0.2 – 0.3 0.3 – 0.4 0.4 – 0.5 0.5 – 0.6 0.6 – 0.7 0.7 – 0.8 0.8 – 0.9 0.9 – 1.0 1.0 – 1.1 1.1 – 1.2 Ventricle contraction – 1 or 2 rectangles, as long as lesser than 3 All chambers relaxation – 1 or 2 or 3 rectangles, as long as lesser than 4 Must shade until the end 1m 3 (a)(i) A – glomerulus; B – collecting duct; 2m (a)(ii) Afferent arteriole’s lumen is bigger than efferent arteriole’s; Creates a high hydrostatic/blood pressure in the glomerulus to force small substances out; 2m (b) Maintain a steep concentration gradient between fluid and blood; (must write properly) Allows waste products to diffuse out of blood into fluid; (reject: “if” answers e.g. if the fluid is not changed…) 2m 4 (a) 6CO2 + 6O2 → C6H12O6 + 6O2; (light energy and chlorophyll written on the arrow); 2m (b) Carbon, hydrogen, oxygen; 1m (c) Proteins in water flea is digested into amino acids; Amino acids is used for growth and repair of cells; 2m 5 (a) Rate of transpiration is higher in environment A than B + 9.8 gh-1 vs 4.7 gh-1; Or Rate of transpiration in environment A is higher than B by 5.1 gh-1; Increase in humidity lowers rate of transpiration; Gentler / lower concentration gradient between water vapour of air spaces of leaves and environment; (must write properly) 3m (b) Did not take into account light intensity; 1m

(c) Prevent evaporation of water from the soil; 1m 6 (a) Double helix structure; 2 strands of polynucleotides that are anti-parallel; 2 strands / each base pair held together by hydrogen bonds; Sugar-phosphate backbone of each strand; Each nucleotide consists of sugar, phosphate group and nitrogen- containing base; 4 types of bases adenine, thymine, cytosine, guanine; Each base pair is either adenine to thymine, or cytosine to guanine; Max 3m (b) (circle correctly the lower strand including the bases); 1m (c) A – transcription; Nucleus; 2m 7 (a) (pondweed → snails → small fishes + “stable shape”); (labels + same width); 2m (b) 90% of energy is lost from one trophic level to the next; (must write properly) Only 10% is successfully transferred into the organism; Energy is lost by heat energy from respiration / uneaten body parts e.g. ____ / undigested body parts e.g _______; Energy availability at the 5th trophic level is too small to ensure organism to survive; Max 3m (c)(i) Eutrophication; 1m (c)(ii) Algae blocks sunlight from penetrating into the depths of the pond; Producers deeper in pond unable to photosynthesise; No photosynthesis + no oxygen production; OR Respiration of all organisms depletes oxygen concentration; Max 2m 8 (a) Type B; Cross C2 creates only offspring of type B + allele of type A is recessive / allele of type B is dominant; 2m (b) Type A parent is homozygous recessive; Type B parent is heterozygous; Offspring inherit 1 allele from type A and 1 allele from type B; 50% chance to create a heterozygous offspring OR ratio of getting type A to type B is 1:1; Max 3m (c) Discontinuous variation; 1m (d) Mutation creates variation in wing patterns; Variations enables the butterfly to adapt to environment + escape from predators / camouflage into the surroundings; Grow to maturity + reproduce successfully; Pass the genes in wing pattern to the next generation; Max 3m

9 (a)(i) Increase from 29 billion metric tons to (approx.) 35 billion metric tons; OR Increase in 6 billion metric tons; From 2008 to 2009 + decrease by 1 billion metric tons; From 2019 to 2020 + decrease by 2 billion metric tons; (capped at 2m) 2m (a)(ii) Deforestation; Burning of fossil fuels; 2m (a)(iii) COVID pandemic + less human activity e.g. public transport; 1m (b) Carbon dioxide is a greenhouse gas + traps heat; Higher temperature, melting of ice in polar regions + raise sea levels / release trapped pathogens; Higher temperature, bleaching of corals + decrease biodiversity; Higher concentration of carbon dioxide in water + decrease pH; Dissolves calcium compounds of shell fishes; Climate change + erratic weather conditions; Climate change + vulnerabilities in some animals e.g. polar bears (temperature) and bees (reproduction cycles of plants); Max 5m 10 (a) Allows more time for pectinase to break down pectin and release the apple juice; 1m (b) Axes + units; Appropriate scale + origin; Plots; Best-fit line; 4m (c) Increase temperature + increase kinetic energy of enzyme and substrate molecules; Increase collision rate of enzyme and substrate molecules; Increase formation of enzyme-substrate complex; Increase formation of product molecules; Max 3m (d) Biological/organic catalyst + protein; Speed up chemical reactions without itself chemically altered after the reaction; 2m 11 (a) Through droplets in the air / airborne transmission + when individual talks / sneezes / coughs; The droplets inhaled by another individual; Exchange of body fluids during sexual intercourse; Baby receiving milk from mother through breastfeeding; Direct contact through mucous membranes e.g. conjunctivitis / HFMD / chicken pox; Transmitted through ingestion of contaminated food / water e.g. cholera, typhoid; Max 4m

(b) HIV destroys/lowers a person’s immune system by destroying white blood cells; Hence the body is unable to produce antibodies to protect the person from foreign pathogens; Person infected might not display signs and symptoms for a long time and may unknowingly transmit the virus during this period of time; Social stigma and discrimination against people who are affected will deter affected individuals from seeking medical treatment; Lack of awareness and education about HIV transmission / HIV prevention / misconceptions about viral infections; High-risk behaviours from affected individuals through sharing of unsterilised needles / sharp instruments due to lack of resources, education, awareness, etc; Limited access to healthcare in low-income / remote areas; Virus is able to mutate rapidly which slows down the research on a vaccine against HIV infection; Hard to track movement of people on a global scale, which can spread the infection; (any four) Max 6m 12 (a) Advantage Only 1 parent is required; High chance that beneficial qualities is passed down to offspring; Does not require external pollinators e.g. wind / insect; High chance of pollination due to close proximity of male and female parts; Less energy is used to produce lesser pollen grains; (any three) Disadvantage Less genetic variation due to only 1 parent; Less adapted to changes in environment; Long-term, offspring becomes weaker