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Primary 6 PSLE Science Practice Paper 5
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TuitionGoWhere Practice Paper - Science Primary 6 PSLE
Answer Key - Version 5 of 5
SECTION A: Multiple Choice Questions (Questions 1–20)
20 marks
| Question | Answer | Explanation |
|---|---|---|
| 1 | C | Rusting is a chemical process that happens to non-living things like iron. Living things show characteristics such as growth, reproduction, and response to stimuli, but they cannot "rust." |
| 2 | B | Plants are living things that can grow, reproduce (by seeds, spores, or other methods), and respond to changes in their environment (such as growing toward light). While plants do make their own food (photosynthesis), this alone does not define them as living—bacteria and some protists also make their own food but are not plants. |
| 3 | C | Following the key: No wings leads to fish or frog; no scales indicates frog. Position X must be the frog. The key uses dichotomous (either/or) choices at each step. |
| 4 | C | Green plants and algae contain chlorophyll and can carry out photosynthesis to make their own food. Fungi and animals cannot make their own food. |
| 5 | C | Fish have a backbone (vertebrate), live in water, and do NOT have wings or feathers. Organism R matches all these characteristics. |
| 6 | B | Spore-producing plants, such as ferns and mosses, reproduce using spores—not seeds, bulbs, or runners. |
| 7 | B | The correct classification order from largest to smallest is: Kingdom → Phylum → Class → Order → Family → Genus → Species. This is the Linnaean system used worldwide by scientists. |
| 8 | A | Fungi lack chlorophyll and cannot photosynthesize. They must absorb nutrients from dead or decaying organic matter through their hyphae. Plants can make their own food using chlorophyll and sunlight. |
| 9 | D | Touch-me-not (Balsam) disperses seeds by explosion of the seed pod. Coconut by water, dandelion by wind, mango by animal (fleshy fruit eaten). |
| 10 | B | Snail population increased from 20 to 35, while butterfly population decreased from 15 to 2. Snails were not most numerous in March (20 vs worms 12, but ladybirds 10—though snails were indeed highest, option B is definitively correct about the trend). |
| 11 | B | Bacteria (Lactobacillus) ferment milk sugar (lactose) into lactic acid, which thickens milk and gives yoghurt its texture and tangy taste. |
| 12 | C | Plastic is a man-made material that microorganisms cannot easily break down. It is non-biodegradable. Paper, vegetable peel, and banana skin are biodegradable. |
| 13 | D | Producers are organisms that can make their own food through photosynthesis. Water plants are the only producers in this food chain. |
| 14 | B | Mammals have backbones (vertebrates), cannot make their own food, have hair or fur, and most give birth to live young. The description matches mammal characteristics perfectly. |
| 15 | C | A wooden table is made from wood, which comes from trees that were once living. Glass, plastic, and metal are non-living materials that were never part of living things (though some metals are extracted from mineral ores, the ore itself was never alive). |
| 16 | B | Dandelion (parachute/pappus) and sycamore (wing) are both adapted for wind dispersal. Coconut floats and is water-dispersed; mango is animal-dispersed through its fleshy fruit. |
| 17 | B | Yeast respires anaerobically, producing carbon dioxide and ethanol. The carbon dioxide gas creates bubbles that make bread rise and become light and fluffy. |
| 18 | B | Mould grows best in warm (around 20-30°C), moist conditions. The graph shows 30°C and 85% humidity—ideal for rapid fungal growth. |
| 19 | C | All living things need energy to carry out life processes such as growth, reproduction, movement, and repair. Some bacteria do not need oxygen (anaerobic), not all can move (plants cannot), and not all reproduce by eggs (binary fission, budding, spores are alternatives). |
| 20 | C | Bread mould (Rhizopus) reproduces asexually by producing spores in sporangia. When the sporangium bursts, spores are released into the air and can land on new food sources to grow. |
SECTION B: Short Answer Questions (Questions 21–35)
40 marks
21. [4 marks]
(a) Insects [1 mark]
Teaching note: Insects are a class of invertebrates (animals without backbones) within the arthropod phylum.
(b) Any two from: [2 marks]
- It has no backbone (invertebrate)
- It has six legs (characteristic of insects—3 pairs)
- It has wings (most adult insects have wings)
- It has feelers/antennae (sensory organs typical of insects)
Marking note: Must give two distinct characteristics that match insect features.
(c) Any correct example: Butterfly / Bee / Ant / Grasshopper / Housefly / Mosquito [1 mark]
22. [7 marks]
(a) [4 marks]
- Order: Carnivora
- Family: Felidae
- Genus: Panthera
- Species: tigris
Teaching note: The complete classification is Kingdom Animalia → Phylum Chordata → Class Mammalia → Order Carnivora → Family Felidae → Genus Panthera → Species tigris. The scientific name is Panthera tigris.
(b) Panthera tigris [1 mark]
Accept: Panthera tigris (either underlined or italicized, or written clearly as two words)
(c) [2 marks]
- Common names vary between languages and regions (e.g., "tiger" in English, "老虎" in Chinese, "harimau" in Malay)
- Scientific names are universal and used by all scientists worldwide
- Prevents confusion between different species that might share common names
- Every species has exactly one unique scientific name
Marking note: Any two valid reasons, 1 mark each.
23. [6 marks]
(a) Organism Q [1 mark] Reason: It has a backbone, has wings, AND has feathers [1 mark]
Teaching note: Feathers are unique to birds among living animals. The combination of backbone (vertebrate), wings, and feathers specifically identifies birds.
(b) Organisms P and R [1 mark] Reason: They can make their own food / they are producers [1 mark]
Teaching note: Only plants, algae, and some bacteria can carry out photosynthesis to make their own food. The presence of this ability strongly indicates plant or plant-like organisms.
(c) Mammals / Amphibians / Reptiles / Fish [1 mark] Acceptable answer with reason: It could be a mammal because mammals have backbones, cannot make their own food, and do not have wings or feathers (or it could be a fish, reptile, or most amphibians).
Reason: [1 mark] must link to the characteristics given—backbone present, no food-making, no wings, no feathers.
24. [8 marks]
(a) To find out if moisture/water affects the growth of mould on bread. [1 mark]
Must mention moisture/water as the factor being tested.
(b) Any two from: [2 marks]
- Same type/brand of bread
- Same size/thickness of bread slice
- Same type of mould spores present initially
- Same duration (7 days)
- Same location/exposure to light
(c) Setups A and B [1 mark] Explanation: [2 marks]
- Both have air and are at room temperature (same conditions)
- Only difference is moisture (A = dry, B = wet)
- This makes it a fair test because only one variable differs
Teaching note: This is the controlled variable principle. To test one factor, all other factors must be kept constant.
(d) [2 marks]
- Moisture/water is needed for mould growth (B had mould, A did not)
- Mould grows better/faster when there is moisture present
Also accept: Temperature affects mould growth too (comparing B and D shows less mould in cold).
25. [8 marks]
(a) Grass and shrubs (either or both) [1 mark]
(b) Any valid four-organism chain, e.g.: [2 marks]
- Grass → Grasshopper → Frog → Snake
- Grass → Grasshopper → Lizard → Snake
- Grass → Mouse → Snake → Hawk
- Shrubs → Deer → ? (no deer predator shown as 4th, so check web)
Must trace actual arrows in diagram. 1 mark for correct sequence, 1 mark for all arrows correct.
(c) [3 marks]
- The population of frogs would decrease [1 mark]
- Frogs feed on grasshoppers / grasshoppers are frogs' food source [1 mark]
- With no grasshoppers, frogs would starve / lack food / not survive [1 mark]
Alternative: If student mentions frogs might eat other things (lizards, etc.), accept if plausible within the food web.
(d) [2 marks]
- A food web shows many interconnected food chains
- Organisms often eat more than one type of food / have multiple food sources
- If one organism is removed, the web shows alternative pathways
- A single food chain is too simple and does not show these complex relationships
26. [6 marks]
(a) Organism Y [1 mark] Reason: It reproduces by binary fission / it feeds on dead organic matter in soil [1 mark]
Teaching note: Binary fission is the characteristic method of reproduction for bacteria. Bacteria are decomposers that break down dead organic matter.
(b) Organism Z [1 mark] Reason: It makes its own food using sunlight / it carries out photosynthesis [1 mark]
Teaching note: Making food using sunlight is the defining characteristic of photosynthetic organisms—plants and algae. Being found on pond surface suggests it may be duckweed or similar aquatic plant.
(c) [2 marks]
- Both are decomposers / feed on dead organic matter / absorb nutrients (if comparing X and Y by feeding method)
- OR: Both reproduce using spores (if comparing X and Z—though Y uses binary fission)
Better answer: Organisms X and Y are both decomposers that break down dead organic matter to obtain nutrients. They help in nutrient recycling in ecosystems.
27. [5 marks]
(a) Pollination [1 mark]
(b) [2 marks]
- After pollination, fertilization occurs
- The pollen tube grows down the style to the ovary
- The male gamete fuses with the female gamete (ovule)
- This fusion of gametes forms a zygote, which develops into an embryo within the seed
Accept key terms: fertilization, fusion of male and female gametes, formation of seeds/embryo.
(c) [2 marks]
- Prevents overcrowding near the parent plant
- Reduces competition for light, water, and nutrients
- Allows plants to colonize new areas / spread to suitable habitats
- Increases chances of survival of the species
Any two points, 1 mark each.
28. [6 marks]
(a) Type D [1 mark] Reason: It has a fleshy, sweet-smelling fruit that attracts animals [1 mark]
Teaching note: Animal-dispersed seeds often have fleshy, tasty, or brightly colored fruits. The animal eats the fruit and excretes the seeds elsewhere.
(b) [2 marks]
- Type A (45 found): fluffy hairs for wind dispersal
- Type C (28 found): wing-like structure for wind dispersal
- Together: 73 out of 108 seeds (about 68%) had wind dispersal features
- This is more than half / the majority of seeds found
(c) [2 marks]
- Seeds beneath parent plant must compete with parent for resources
- Limited space for growth
- Less light available due to parent plant shading
- Greater chance of disease/pest transfer from parent
- Reduced genetic diversity in population
Any two valid points, 1 mark each.
29. [8 marks]
(a) [2 marks]
- To collect the gas produced by the plant
- The water prevents the gas from escaping
- The inverted position traps gas at the top as bubbles rise
(b) Oxygen [1 mark] Test: Insert a glowing splint into the gas [1 mark] Result: The glowing splint relights / bursts into flame [1 mark]
Teaching note: Oxygen supports combustion, so it rekindles a glowing splint. This is the standard test for oxygen.
(c) [3 marks]
- The rate would decrease / fewer bubbles would be produced [1 mark]
- Light intensity decreases as distance increases [1 mark]
- Photosynthesis requires light energy; less light means slower rate of photosynthesis / less oxygen produced [1 mark]
Teaching note: Light intensity follows the inverse square law; students at P6 level need only understand that more distance = less light = slower photosynthesis.
30. [6 marks]
(a) Asexual reproduction / Vegetative reproduction [1 mark]
Either term acceptable. "Asexual" preferred.
(b) [2 marks]
- Faster than growing from seeds (no need for pollination, fertilization, seed formation)
- Identical/clone offspring—preserves desirable characteristics of parent
- More reliable success rate than seeds in some conditions
Any one advantage with explanation, 2 marks.
(c) Method A (Runners) [1 mark] Explanation: [2 marks]
- Strawberries naturally produce runners/stolons that grow along the ground
- At nodes on the runner, new daughter plants develop with roots and shoots
- These can be separated and planted as genetically identical copies of the parent
- This is faster than growing from seed and ensures all plants have the same desirable traits (taste, size, disease resistance)
31. [6 marks]
(a) Gills [1 mark]
Teaching note: The gills (lamellae) on the underside of the cap are lined with basidia that produce spores.
(b) [3 marks]
- Mushrooms need moisture for spore germination and hyphal growth [1 mark]
- Darkness prevents desiccation/drying out [1 mark]
- Decomposers grow where there is dead organic matter (rotting wood, leaf litter, soil) which is typically found in damp, shaded areas [1 mark]
- Warm temperatures speed up metabolic processes [additional, not required]
Any three valid points, 1 mark each.
(c) [2 marks] Any two from:
- Fungi cannot make their own food (no chlorophyll); plants can photosynthesize
- Fungi absorb nutrients through hyphae; plants make food in leaves
- Fungi have cell walls made of chitin; plants have cell walls made of cellulose
- Fungi reproduce by spores (not seeds like most plants)
- Fungi are not green in color (lack chlorophyll)
Any two distinct differences, 1 mark each.
32. [8 marks]
(a) Woodland edge [1 mark] Evidence: [2 marks]
- Has the highest total number of species: 35 plant + 28 animal = 63 species
- Higher than Pond (15+22=37), Grassland (25+18=43), Flower garden (20+15=35)
- Has highest in both categories (plants AND animals)
Must show evidence of calculation or clear comparison to get both marks.
(b) [2 marks]
- Ponds contain many different microhabitats (surface, open water, bottom mud, plants, edges)
- Aquatic animals include insects, fish, amphibians, crustaceans, mollusks, larvae, etc.
- Some animals are temporary visitors (birds, mammals coming to drink)
- Aquatic ecosystems support diverse food webs
Any two valid points, 1 mark each.
(c) [3 marks]
- Biodiversity would decrease [1 mark]
- Habitats would be destroyed/cleared for construction [1 mark]
- Plants would be removed, removing food sources and shelter for animals
- Noise and human activity would disturb/displace animals
- Pollution from construction might affect remaining organisms
Prediction: decrease, 1 mark. Two valid explanations, 1 mark each.
33. [5 marks]
(a) Stamen [1 mark]
Teaching note: The stamen consists of anther + filament and is the male reproductive part.
(b) [2 marks]
- The stigma is sticky / has a rough surface
- This helps trap/catch pollen grains when they land on it
- Often feathery or broad to increase surface area for catching pollen
Structure feature, 1 mark; function linked to pollination, 1 mark.
(c) [2 marks]
- Ovules develop into seeds (after fertilization)
- Ovary develops into a fruit (to protect and disperse the seeds)
34. [7 marks]
(a) To exclude light / control for light as a variable / to ensure light does not affect the results [1 mark]
Teaching note: Light is needed for photosynthesis, not germination. By excluding light, the experiment tests only water, air, and temperature.
(b) It acts as a control / to compare with the other setups / to show normal germination conditions [1 mark]
(c) [2 marks]
- Seeds need water to activate enzymes that break down stored food
- Water is needed for chemical reactions to begin
- Stored food must be transported in solution to growing embryo
- Water softens the seed coat to allow the radicle to emerge
Any two points, 1 mark each.
(d) [3 marks]
- Water [1 mark]
- Air/oxygen [1 mark]
- Suitable/warm temperature [1 mark]
35. [9 marks]
(a) [2 marks] Any two from:
- Algae bloom covering the water surface
- Water became murky/green
- Fish died / floating dead fish
- Fewer visible animals
- Reduced plant diversity / fewer water plants
(b) [2 marks]
- Fertilizers contain nitrogen and phosphorus / minerals / nutrients
- These are food for algae
- Excess nutrients cause rapid algae growth / algal bloom
(c) [3 marks]
- Algae cover the surface, blocking sunlight [1 mark]
- Submerged plants cannot photosynthesize and die [1 mark]
- Bacteria decompose dead plants and algae, using up oxygen in the water [1 mark]
- Fish suffocate / lack oxygen and die
Alternative pathway: Respiration by excessive algae at night uses up oxygen; decomposition of dead algae uses oxygen.
(d) [2 marks] Any two from:
- Use less fertilizer on farms / apply fertilizer more carefully
- Create buffer zones / vegetation strips between farms and water
- Treat farm runoff before it enters waterways
- Use organic farming methods / slow-release fertilizers
- Regularly monitor water quality
SECTION C: Structured Application Questions (Questions 36–40)
40 marks
36. [20 marks]
(a) [2 marks]
- The higher the temperature, the faster bacteria grow (up to a certain limit)
- OR: Bacteria grow fastest at 37°C and slowest at 5°C
- Must state a clear testable relationship between temperature and bacterial growth
(b) [5 marks]
Independent variable: Temperature [1 mark]
Dependent variable: Area covered by bacteria / percentage of dish covered / amount of bacterial growth [1 mark]
Controlled variables (any three): [3 marks]
- Same type/strain of bacteria
- Same amount/type of nutrient agar
- Same size of petri dish
- Same duration of incubation (48 hours)
- Same method of inoculation / same starting amount of bacteria
- Same sealing method / same air exposure
(c) [4 marks]
Marking for graph:
- Correctly labelled axes with units [1 mark]
- Correct scale on both axes [1 mark]
- All three points accurately plotted [1 mark]
- Line drawn correctly (straight line or smooth curve through points) [1 mark]
Expected shape: upward trend from 5°C to 37°C, showing positive correlation between temperature and bacterial growth rate.
(d) [2 marks]
- As temperature increases, the area covered by bacteria increases
- The relationship is directly proportional / positive correlation
- The rate of increase becomes steeper as temperature rises
- OR: Growth is slow at low temperatures and rapid at higher temperatures
(e) [2 marks]
- 37°C is body temperature / near human body temperature
- Many bacteria that affect humans are adapted to this temperature
- Enzymes in bacteria work most efficiently / optimally at this temperature
- Metabolic reactions occur fastest at this temperature
(f) [3 marks]
- Prediction: Very little/no growth / 0-5% coverage [1 mark]
- 60°C is too hot for most bacteria to survive [1 mark]
- Enzymes are denatured / damaged at high temperatures [1 mark]
- Proteins lose their shape and metabolism stops / cells die
(g) [2 marks]
- To prevent contamination from other microorganisms in the air
- To prevent the escape of bacteria into the environment (safety)
- To maintain sterile conditions inside the dish
- To keep the same air/moisture conditions in each dish
37. [11 marks]
(a) The passage states that 91% of ocean species may not yet be discovered / most ocean species are undiscovered. [1mark]
(b) [2 marks]
- Plants can make their own food using sunlight (photosynthesis) [1 mark]
- Fungi cannot make their own food — they must absorb nutrients from their surroundings [1 mark]
Must use information from passage—direct quote or clear paraphrase.
(c) [3 marks]
- Habitat destruction / habitats destroyed for farms, roads, cities
- Pollution (of air, water, soil)
- Climate change / altering temperature and rainfall patterns
1 mark each. Must be from passage.
(d) [3 marks]
- Destroying habitats removes homes/food sources/breeding places for organisms [1 mark]
- Organisms may die or be forced to move to unsuitable areas [1 mark]
- Many specialist species cannot survive elsewhere / biodiversity decreases when habitats are lost [1 mark]
- Food webs are disrupted / populations cannot be sustained
(e) [2 marks]
- To preserve genetic diversity for future use
- To allow breeding/restoration if species become endangered later
- Climate change might make currently common plants vulnerable in future
- Unknown future benefits — medicinal, agricultural, or ecological uses
38. [12 marks]
(a) To show the rate of photosynthesis / as an indicator of how much photosynthesis is occurring [1 mark]
Teaching note: More bubbles = faster rate of photosynthesis. The bubbles are oxygen released as a byproduct.
(b) [2 marks]
- Tube A has all normal conditions for photosynthesis
- It acts as a control / standard for comparison
- It shows the normal rate with which other setups can be compared
- Without it, we cannot tell if changed conditions increase or decrease photosynthesis
(c) [3 marks]
- Tube A (bright light): many/rapid bubbles [1 mark]
- Tube B (dim light): few/slow bubbles [1 mark]
- Conclusion: Greater light intensity increases rate of photosynthesis / photosynthesis needs light; more light = faster rate
(d) [2 marks]
- Enzymes work slowly at low temperatures / cold slows down chemical reactions [1 mark]
- Temperature affects enzyme activity / metabolic rate of plant cells [1 mark]
- Even with sufficient light, the chemical reactions of photosynthesis cannot proceed quickly when cold
Teaching note: The light-dependent reactions may still occur, but the Calvin cycle (light-independent) is enzyme-controlled and temperature-sensitive.
(e) [3 marks]
- Baking soda provides extra carbon dioxide (sodium bicarbonate releases CO₂ in water) [1 mark]
- Carbon dioxide is a raw material / reactant for photosynthesis [1 mark]
- More CO₂ available means more glucose can be produced, so faster rate / more oxygen released as byproduct [1 mark]
(f) Amount of chlorophyll / type of plant / water availability / pH / mineral nutrients [1 mark]
Any valid factor not already tested in the experiment.
39. [10 marks]
(a) [2 marks] Example: Rose → Aphid → Ladybird → Small bird → Sparrowhawk [2 marks]
Or any valid chain ending with sparrowhawk. Must be traceable from food web. 1 mark if one organism/link wrong but direction correct.
(b) [3 marks]
- Pesticide killed the aphids (or ladybirds directly if contact pesticide) [1 mark]
- Aphids were the food source for ladybirds [1 mark]
- Without aphids, ladybirds starved / lacked food / could not survive / reproduced less [1 mark]
Alternative: If pesticide killed ladybirds directly: poison absorbed through exoskeleton / contact with pesticide residues.
(c) [3 marks]
- Pesticide killed earthworms and other soil organisms [1 mark]
- These organisms normally break down organic matter / recycle nutrients in the soil [1 mark]
- Without them, nutrients were not returned to the soil / soil became poor, causing nutrient deficiency in roses [1 mark]
Alternative pathway: Pesticide may have killed nitrogen-fixing bacteria or mycorrhizal fungi that help nutrient uptake.
(d) [2 marks]
- Bees may have been killed by direct contact with pesticide [1 mark]
- Or: Fewer flowers / nectar sources as other plants affected
- Or: Pesticide accumulated in system, affecting insects
- Bees are insects—the pesticide targets insects (aphids), so affects beneficial insects too
40. [13 marks]
(a) [3 marks]
- X: Seed coat / Testa
- Y: Radicle
- Z: Plumule
1 mark each. Must match labelling—accept close equivalents (e.g., "protective outer layer" for testa).
(b) [2 marks]
- The stored food (starch, oils, proteins) provides energy for the growing embryo [1 mark]
- Before the seedling can make its own food by photosynthesis, it depends on stored reserves in the cotyledons [1 mark]
(c) [3 marks]
- The radicle grows downward due to gravitropism / geotropism (positive) [1 mark]
- Roots grow toward gravity to anchor the plant and absorb water and minerals from the soil [1 mark]
- The plumule grows upward due to negative gravitropism / phototropism [1 mark]
- Shoots grow away from gravity / toward light to reach above ground for photosynthesis
Teaching note: Tropisms are growth responses. Positive gravitropism = growth with gravity (roots); negative gravitropism = growth against gravity (shoots).*
(d) [2 marks]
- Soaking speeds up germination by providing water immediately [1 mark]
- Ensures uniform hydration of all seeds [1 mark]
- Softens the seed coat to allow embryo to emerge more easily
- Activates enzymes needed to break down stored food
Any two valid points, 1 mark each.
(e) [3 marks]
- The seed planted 1 cm deep would germinate better [1 mark]
- The surface seed may dry out / be eaten by birds or animals / be washed away by rain [1 mark]
- Soil provides protection, moisture retention, and stable temperature for the buried seed [1 mark]
- However, too deep is also bad—the seed may run out of energy before reaching the surface
Teaching note: Optimal planting depth varies by seed size, but 1 cm is reasonable for medium seeds. The key concept is that surface conditions are harsher than protected soil conditions.*
END OF ANSWER KEY
Total Marks: 100
Note: This answer key provides teaching-oriented explanations suitable for students learning the Diversity topic. All content is syllabus-aligned with the Singapore Primary Science curriculum and PSLE preparation standards.