Temasek Sec 2024 Prelim 4E BIO ANS

1 Temasek Secondary School 6093 Biology Prelim 2024 Answers PAPER 1 (40 marks) No Answer No Answer 1 C 21 D 2 A 22 C 3 B 23 B 4 D 24 C 5 B 25 D 6 C 26 A 7 B 27 B 8 B 28 C 9 A 29 B 10 B 30 D 11 C 31 C 12 C 32 B 13 C 33 D 14 D 34 C 15 B 35 B 16 D 36 B 17 A 37 B 18 A 38 C 19 D 39 A 20 C 40 C

2 6093 Biology Prelim 2024 Answers Paper 2 Answers Qn Answer Remarks 1a Insect pollination; Large petals REJECT: colourful petals / scent / nectar guides / compact stigma Both for 1 m bi A sepal / calyx B petal / corolla C fruit / ovary D style Any error deducts 0.5 m bii E produces the pollen biii Circle and name the stigma. [1] (structure tip of style) Both are female parts that receive the male gametes or pollen which contain male gametes. [1] OWTTE 2a Smoking. Cigarette smoke contains tar that can cause uncontrolled cell division Both points 1 m b • Tumor / lumps of cells blocks the alveolar wall / alveolar space / alveoli / bronchiole space / makes the alveolar wall less elastic / less able to inflate/ deflate / reduces surface area of alveoli [1] • This reduces the volume in the lungs [0.5] and increases pressure in the lungs. [0.5] / Decreases the surface area for gaseous exchange / diffusion hence lower rate of diffusion of gaseous [1] • During inhalation, less air can be forced into the lungs / during exhalation less air can flow out of the lungs / there will be breathing difficulty [1] c Patient has a slower rate of fat digestion by lipase [1] due to less / little bile released into gall bladder hence duodenum. [0.5] Lesser / no emulsification of fats can occur. SA:V of fat droplets / globules remain low. [0.5]

3 Qn Answer Remarks d Non-infectious as it cannot be spread from person to person and not caused by pathogens 3a Voluntary as the action is controlled consciously / by choice / initiated by her b Nerve impulse initiated in her brain [0.5] Transmitted via the relay neurone [0.5] from the brain to the spinal cord [0.5] In the spinal cord the nerve impulse is transmitted across a synapse to the motor neurone [0.5] The motor neurone transmits the nerve impulse to the bicep muscles [0.5] Bicep muscles contract to move her arm to lift the tool [0.5] c Any one: Water pollution: There will not be any insecticides / fertiliser in the nearby water bodies reducing / no / less water pollution / cleaner water [0.5] • So no bioaccumulation and biomagnification [0.5] of non-biodegradable substances up the food chain, [0.5] top consumers are not harmed [0.5] • No eutrophication / algal bloom / growth of algae will occur [0.5] so no death/decomposition of water plants by bacteria, no increase in bacterial growth [0.5] thus no oxygen depletion in water / water continues to have high oxygen [0.5 ] Biodiversity: Insects in the ecosystem/ habitat not killed by insecticides [0.5] • There will be an increase in biodiversity / no loss of biodiversity [0.5] Insect pollinators of the crops / plants can continue pollination [0.5]

4 Qn Answer Remarks greater variety of plant species can be pollinated [0.5] 4a Movement increases rate of respiration which releases more heat [1] thus would increase his body temperature / increase in sweating b The internal body temperature near the brain decreases from 37.4 oC to 37.06 oC. [1] Blood in the capillaries (at the mouth / stomach) is cooled by the ice-cold drink. [0.5] The cooled blood flows to the brain [0.5] c Thermoreceptors in the brain [1] d The rate of sweating decreases from 3.6 to 0.9 arbitrary units.[1] Less water evaporates from the skin surface [0.5], reducing heat loss in the form of latent heat [0.5] 5a Water content decreases steeply from 76 % to 74% initially and decreases further to 73.8% / when crabs first moved / from day 0 to day 4.5 [0.5] before i ncreasing gradually to 75% at day 15. [0.5] Sea water has a lower water potential th an cytoplasm of crab’s muscle cells, [0.5] water moves out of the crab’s muscle cell via osmosis [0.5] As the amino acid content in the muscle cells increases, the water potential of the muscle cell cytoplasm decreases to be / becomes lower than that of sea water [0.5] Water moves into the cells via osmosis [0.5] b Amino acids lowers the water potential of the crabs cells to prevent dehydration when in sea water

5 Qn Answer Remarks c concentration of amino acids in blood remains similar after a meal [0.5] the excess amino acids transported to liver are deaminated [0.5] in the liver into urea and glucose [0.5] blood leaving the liver via hepatic vein will not have excess amino acids [0.5] 6a Fast-twitch muscle fibres have low myoglobin content, thus low supply/ store of oxygen They rely on anaerobic respiration [0.5] to release additional energy to meet energy demand of vigorous exercise [0.5] by converting glucose to lactic acid. [0.5] Build up of lactic acid causes fatigue [0.5] c Mitochondrion / Mitochondria. [1] (Slow-twitch muscle fibres has more myoglobin hence larger supply of oxygen.) d Long-distance race requires slower and lower intensity muscular contraction over a longer period of time. [1] Since slow-twitching muscle fibres contract slowly over a longer period of time, they have lower overall energy demand and lower oxygen demand [1] Breathing rate and heart rate during the race are able to supply sufficient oxygen (and glucose) to slow -twitch muscle fibers during long- distance races to carry out aerobic respiration. [1] 7a Carbon dioxide is absorbed during photosynthesis and released during respiration. [1] Rate of photosynthesis of the pondweed equals to the rate of respiration of both pondweed and snail. [1] Need to have idea of direction Rej: converted Idea of rate [0.5]

6 Qn Answer Remarks Both snails and pondweed respire [0.5] b Pondweed unable to photosynthesise due to absence of light. [1] Carbon dioxide is not absorbed, but continued to be released when snail and pondweed respire. [1] Unable to photosynthesise [0.5] idea of absorbed [0.5], released [0.5] c From yellow to (red then) purple Qn focus on over the next few hours Starting colour [0.5] final clour [0.5] Change must have “from” “to” 8a The offsprings have similar beak depth to their parents Not trend but must compare the actual beak depth of parent and offspring Scatterplot x and y reading should be simillar b Both continuous and discontinuous variations. Size of ground finish is discontinuous as there are only 2 discrete/ distinct phenotypes, small and medium. [1] Beak depth is continuous variation as there are many values over a range, from 7 to 17 mm. [1] c Finches on Isabela Island have a larger range of beak depth, between 10 to 16.5 mm, while finches on Daphne Island have a narrower range of beak depth between 8.5 to 11.5 mm. / Highest percentage of finches on Isabela Island has beak depth of 12 mm, while on Daphne Island is 10 mm. [1] 1. Idea of mutation leads to variation Ancestor/ coloniser finches on Daphne Island have a range of beak depth due to random mutation / different combination of alleles of one / several genes. [1] Mark can be awarded if mentioned later on in answer Answer should focus on Daphne island

7 Qn Answer Remarks 2. Selector on Daphne Island Daphne Island have smaller seeds than on Isabela Island [1] 3. Phenotype/ trait with advantage and effect of having advantage Finches with s hallower beaks on Daphne Island are able to feed on the smaller seeds better, have sufficient food to survive and reproduce [1] They are able to pass on their genes to their offspring, increasing the population of finches with shallower beaks (8.5-11.5 mm) [1]